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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
quant-ph/0609064 | Arti Chamoli | Arti Chamoli and C. M. Bhandari | Groverian entanglement measure and evolution of entanglement in search
algorithm for n(=3 and 5)-qubit systems with real coefficients | 13 pages, 2 figures | null | null | null | quant-ph | null | Evolution of entanglement with the proceeding of quantum algorithms affects
the outcome of the algorithm. Particularly, the performance of Grover's search
algorithm gets worsened if the initial state of the algorithm is an entangled
one. The success probability of search can be seen as an operational measure of
entanglement. This paper demonstrates an entanglement measure based on the
performance of Grover's search algorithm for three and five qubit systems. We
also show that although the overall pattern shows growth of entanglement, its
rise to a maximum and then consequent decay, the presence of local fluctuation
within each iterative step is likely.
| [
{
"version": "v1",
"created": "Fri, 8 Sep 2006 15:07:13 GMT"
},
{
"version": "v2",
"created": "Fri, 4 May 2007 19:31:03 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Chamoli",
"Arti",
""
],
[
"Bhandari",
"C. M.",
""
]
]
|
quant-ph/0609065 | Rubens Ramos Viana | Fabio Alencar Mendonca and Rubens Viana Ramos | Hybrid Parallel Quantum Key Distribution Protocol | 16 pages, 4 figures | null | null | null | quant-ph | null | The practical realizations of BB84 quantum key distribution protocol using
single-photon or weak coherent states have normally presented low efficiency,
in the meaning that most bits sent by Alice are not useful for the final key.
In this work, we show an optical setup to improve the transmission rate of
useful bits putting together two ideas, parallel quantum key distribution and
physical encryption using mesoscopic coherent states. The final result is a
four time faster quantum key distribution setup.
| [
{
"version": "v1",
"created": "Fri, 8 Sep 2006 16:20:39 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Mendonca",
"Fabio Alencar",
""
],
[
"Ramos",
"Rubens Viana",
""
]
]
|
quant-ph/0609066 | Dmitriy Kulikov Alexandrovitch | D. A. Kulikov, R. S. Tutik | Renormalization of expansions for Regge trajectories of the
Schr\"odinger equation | 5 pages, no figures | Dniepropetrovsk National University Scientifical Herald. Series
Physics and Radiophysics, Vol.12, pp. 28-32 (2005) | null | null | quant-ph | null | A recursion technique for the renormalization of semiclassical expansions for
the Regge trajectories of bound states of the Schr\"odinger equation is
developed. As an application of the proposed technique, the two-parameter
renormalization scheme of the Regge trajectories for the bound states in the
Martin potential is considered.
| [
{
"version": "v1",
"created": "Sun, 10 Sep 2006 13:36:44 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Kulikov",
"D. A.",
""
],
[
"Tutik",
"R. S.",
""
]
]
|
quant-ph/0609067 | Daniel A. Lidar | Ari Mizel, Daniel A. Lidar, Morgan Mitchell | Simple proof of equivalence between adiabatic quantum computation and
the circuit model | 5 pages, 2 figures. v2: improved gap estimates and added some more
details | Phys. Rev. Lett. 99, 070502 (2007) | 10.1103/PhysRevLett.99.070502 | null | quant-ph | null | We prove the equivalence between adiabatic quantum computation and quantum
computation in the circuit model. An explicit adiabatic computation procedure
is given that generates a ground state from which the answer can be extracted.
The amount of time needed is evaluated by computing the gap. We show that the
procedure is computationally efficient.
| [
{
"version": "v1",
"created": "Fri, 8 Sep 2006 21:22:30 GMT"
},
{
"version": "v2",
"created": "Mon, 26 Feb 2007 07:29:52 GMT"
}
]
| 2007-09-06T00:00:00 | [
[
"Mizel",
"Ari",
""
],
[
"Lidar",
"Daniel A.",
""
],
[
"Mitchell",
"Morgan",
""
]
]
|
quant-ph/0609068 | Sergio Boixo | Sergio Boixo, Lorenza Viola, and Gerardo Ortiz | Generalized Coherent States as Preferred States of Open Quantum Systems | 5 pages, no figures; Significantly improved presentation, new
derivation of invariant uncertainty measure via quantum Fisher information
added. | EPL, 79 (2007) 40003 | 10.1209/0295-5075/79/40003 | null | quant-ph | null | We investigate the connection between quasi-classical (pointer) states and
generalized coherent states (GCSs) within an algebraic approach to Markovian
quantum systems (including bosons, spins, and fermions). We establish
conditions for the GCS set to become most robust by relating the rate of purity
loss to an invariant measure of uncertainty derived from quantum Fisher
information. We find that, for damped bosonic modes, the stability of canonical
coherent states is confirmed in a variety of scenarios, while for systems
described by (compact) Lie algebras stringent symmetry constraints must be
obeyed for the GCS set to be preferred. The relationship between GCSs,
minimum-uncertainty states, and decoherence-free subspaces is also elucidated.
| [
{
"version": "v1",
"created": "Sat, 9 Sep 2006 01:21:18 GMT"
},
{
"version": "v2",
"created": "Fri, 29 Sep 2006 00:29:15 GMT"
},
{
"version": "v3",
"created": "Mon, 2 Apr 2007 16:55:10 GMT"
}
]
| 2008-01-23T00:00:00 | [
[
"Boixo",
"Sergio",
""
],
[
"Viola",
"Lorenza",
""
],
[
"Ortiz",
"Gerardo",
""
]
]
|
quant-ph/0609069 | Nikolai Chuprikov | N. L. Chuprikov | New Model of One-dimensional Completed Scattering and the Problem of
Quantum Nonlocality | 5 pages; no figures; submitted to Proceedings of Foundations of
Probability and Physics -4, 2006, Vaxjo, Sweden | null | 10.1063/1.2713468 | null | quant-ph | null | The origin of nonlocality in quantum mechanics (QM) is analyzed from the
viewpoint of our new model of a one-dimensional (1D) completed scattering. Our
study of quantum nonlocality complements those carried out by Volovich and
Khrennikov. They pointed to an unphysical character of nonlocality in Bell's
theorem whose context does not contain the very structure of the space-time.
However, there is another reason leading to nonlocality in QM. The existing
model of a 1D completed scattering evidences that QM, as it stands, even with a
proper space-time context, contradicts special relativity. By our model this
scattering process represents an entanglement of two coherently evolved
alternative sub-processes, transmission and reflection; whose characteristics
are measured well after the scattering event. Quantum nonlocality appears in
this problem due to the inconsistency of the superposition principle with the
corpuscular properties of a particle. It can take part only in one of the
sub-processes. However the superposition principle allows introducing
observables common for them. In the fresh wording, this principle must forbid
introducing observables for entangled states.
| [
{
"version": "v1",
"created": "Sat, 9 Sep 2006 06:38:00 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Chuprikov",
"N. L.",
""
]
]
|
quant-ph/0609070 | Gavin K. Brennen | Stephen S. Bullock and Gavin K. Brennen | Qudit surface codes and gauge theory with finite cyclic groups | 26 pages, 5 figures | J.Phys.A40:3481-3505,2007; J.Phys.A40:3481-3506,2007 | 10.1088/1751-8113/40/13/013 | null | quant-ph | null | Surface codes describe quantum memory stored as a global property of
interacting spins on a surface. The state space is fixed by a complete set of
quasi-local stabilizer operators and the code dimension depends on the first
homology group of the surface complex. These code states can be actively
stabilized by measurements or, alternatively, can be prepared by cooling to the
ground subspace of a quasi-local spin Hamiltonian. In the case of spin-1/2
(qubit) lattices, such ground states have been proposed as topologically
protected memory for qubits. We extend these constructions to lattices or more
generally cell complexes with qudits, either of prime level or of level
$d^\ell$ for $d$ prime and $\ell \geq 0$, and therefore under tensor
decomposition, to arbitrary finite levels. The Hamiltonian describes an exact
$\mathbb{Z}_d\cong\mathbb{Z}/d\mathbb{Z}$ gauge theory whose excitations
correspond to abelian anyons. We provide protocols for qudit storage and
retrieval and propose an interferometric verification of topological order by
measuring quasi-particle statistics.
| [
{
"version": "v1",
"created": "Sun, 10 Sep 2006 21:05:10 GMT"
},
{
"version": "v2",
"created": "Tue, 12 Sep 2006 16:41:12 GMT"
}
]
| 2008-11-26T00:00:00 | [
[
"Bullock",
"Stephen S.",
""
],
[
"Brennen",
"Gavin K.",
""
]
]
|
quant-ph/0609071 | Gerardo Adesso | Gerardo Adesso, Alessio Serafini, and Fabrizio Illuminati | Optical state engineering, quantum communication, and robustness of
entanglement promiscuity in three-mode Gaussian states | 33 pages, 10 figures (some low-res due to size constraints), IOP
style; (v2) improved and reorganized, accepted for publication in New Journal
of Physics | New J. Phys. 9, 60 (2007) | 10.1088/1367-2630/9/3/060 | null | quant-ph cond-mat.stat-mech math-ph math.MP physics.optics | null | We present a novel, detailed study on the usefulness of three-mode Gaussian
states states for realistic processing of continuous-variable quantum
information, with a particular emphasis on the possibilities opened up by their
genuine tripartite entanglement. We describe practical schemes to engineer
several classes of pure and mixed three-mode states that stand out for their
informational and/or entanglement properties. In particular, we introduce a
simple procedure -- based on passive optical elements -- to produce pure
three-mode Gaussian states with {\em arbitrary} entanglement structure (upon
availability of an initial two-mode squeezed state). We analyze in depth the
properties of distributed entanglement and the origin of its sharing structure,
showing that the promiscuity of entanglement sharing is a feature peculiar to
symmetric Gaussian states that survives even in the presence of significant
degrees of mixedness and decoherence. Next, we discuss the suitability of the
considered tripartite entangled states to the implementation of quantum
information and communication protocols with continuous variables. This will
lead to a feasible experimental proposal to test the promiscuous sharing of
continuous-variable tripartite entanglement, in terms of the optimal fidelity
of teleportation networks with Gaussian resources. We finally focus on the
application of three-mode states to symmetric and asymmetric telecloning, and
single out the structural properties of the optimal Gaussian resources for the
latter protocol in different settings. Our analysis aims to lay the basis for a
practical quantum communication with continuous variables beyond the bipartite
scenario.
| [
{
"version": "v1",
"created": "Sat, 9 Sep 2006 15:29:38 GMT"
},
{
"version": "v2",
"created": "Wed, 14 Feb 2007 16:51:19 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Adesso",
"Gerardo",
""
],
[
"Serafini",
"Alessio",
""
],
[
"Illuminati",
"Fabrizio",
""
]
]
|
quant-ph/0609072 | Peter Henselder | Peter Henselder | Deformed Geometric Algebra and Supersymmetric Quantum Mechanics | 5 pages | null | 10.1016/j.physleta.2006.11.043 | null | quant-ph | null | Deforming the algebraic structure of geometric algebra on the phase space
with a Moyal product leads naturally to supersymmetric quantum mechanics in the
star product formalism.
| [
{
"version": "v1",
"created": "Sat, 9 Sep 2006 16:52:59 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Henselder",
"Peter",
""
]
]
|
quant-ph/0609073 | Fedor Herbut | Fedor Herbut | On bipartite pure-state entanglement structure in terms of
disentanglement | 41 page, 2 diagrams | J. Math. Phys. 47, 122103 (2006); Virtual Journal of Quantum
Information 6(12), 2006 - Information Theory section | 10.1063/1.2375035 | null | quant-ph | null | Schroedinger's disentanglement [E. Schroedinger, Proc. Cambridge Phil. Soc.
31, 555 (1935)], i. e., remote state decomposition, as a physical way to study
entanglement, is carried one step further with respect to previous work in
investigating the qualitative side of entanglement in any bipartite state
vector. Remote measurement (or, equivalently, remote orthogonal state
decomposition) from previous work is generalized to remote linearly-independent
complete state decomposition both in the non-selective and the selective
versions. The results are displayed in terms of commutative square diagrams,
which show the power and beauty of the physical meaning of the (antiunitary)
correlation operator inherent in the given bipartite state vector. This
operator, together with the subsystem states (reduced density operators),
constitutes the so-called correlated subsystem picture. It is the central part
of the antilinear representation of a bipartite state vector, and it is a kind
of core of its entanglement structure. The generalization of previously
elaborated disentanglement expounded in this article is a synthesis of the
antilinear representation of bipartite state vectors, which is reviewed, and
the relevant results of Cassinelli et al. [J. Math. Analys. and Appl., 210, 472
(1997)] in mathematical analysis, which are summed up. Linearly-independent
bases (finite or infinite) are shown to be almost as useful in some quantum
mechanical studies as orthonormal ones. Finally, it is shown that
linearly-independent remote pure-state preparation carries the highest
probability of occurrence. This singles out linearly-independent remote
influence from all possible ones.
| [
{
"version": "v1",
"created": "Sat, 9 Sep 2006 19:12:14 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Herbut",
"Fedor",
""
]
]
|
quant-ph/0609074 | Jianda Wu | Jian-da Wu, Jian-lan Chen, Yong-de Zhang | The Generation and Exchange of Entanglement via Zeeman Effect | 9 pages, 1 figure | null | null | null | quant-ph | null | In this paper we show a new way to generate entanglement via two identical
three-level atoms splitting in the magnetic field interacting with the cavity
field. By the system we investigate, We can acquire the EPR state,
multi-dimensional entangled states etc. which are more stable than usual
realization by high-energy-level Rydberg atoms and we can realize the local
exchange operator too. We also achieve the goal of maintaining long- time
entanglement between atoms. At last, by using the procedure of local exchange,
we put forward an experimental scheme for quantum feedback.
| [
{
"version": "v1",
"created": "Sun, 10 Sep 2006 06:31:10 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Wu",
"Jian-da",
""
],
[
"Chen",
"Jian-lan",
""
],
[
"Zhang",
"Yong-de",
""
]
]
|
quant-ph/0609075 | Joel Gilmore | Joel Gilmore and Ross H. McKenzie | Quantum dynamics of electronic excitations in biomolecular chromophores:
role of the protein environment and solvent | 22 pages, 4 figures | null | null | null | quant-ph cond-mat.soft | null | We consider continuum dielectric models as minimal models to understand the
effect of a surrounding globular protein and solvent on the quantum dynamics of
electronic excitations in a biological chromophore. We derive expressions for
the frequency dependent spectral density which describes the coupling of the
electronic levels in the chromophore to its environment. The magnitude and
frequency dependence of the spectral density determines whether or not the
quantum dynamics is coherent or incoherent, and thus whether on not one can
observe quantum interference effects such as Rabi oscillations. We find the
contributions to the spectral density from each component of the chromophore
environment: the bulk solvent, protein, and water bound to the protein. The
relative importance of each component to the quantum dynamics of the
chromophore is determined by the dynamics' time scale. Our results provide a
natural explanation and model for the different time scales observed in the
spectral density extracted from the solvation dynamics probed by ultra-fast
laser spectroscopy techniques such as the dynamic Stokes shift and three pulse
photon echo spectroscopy. Our results are used to define under what conditions
the dynamics of the excited chromophore is dominated by the surrounding protein
and when it is dominated by dielectric fluctuations in the solvent. We show
that even when the chromophore is shielded from the solvent by the protein
ultra-fast solvation can be dominated by the solvent. We suggest that the
ultra-fast solvation recently seen in some biological chromophores should not
necessarily be assigned to ultra-fast protein dynamics. Spectral densities
estimated from our continuum models and extracted from experiment suggest that
most quantum dynamics of electronic excitations is incoherent.
| [
{
"version": "v1",
"created": "Mon, 11 Sep 2006 02:36:25 GMT"
},
{
"version": "v2",
"created": "Thu, 19 Oct 2006 03:46:53 GMT"
},
{
"version": "v3",
"created": "Tue, 19 Jun 2007 07:00:39 GMT"
},
{
"version": "v4",
"created": "Mon, 25 Jun 2007 00:48:44 GMT"
}
]
| 2007-06-25T00:00:00 | [
[
"Gilmore",
"Joel",
""
],
[
"McKenzie",
"Ross H.",
""
]
]
|
quant-ph/0609076 | Michael J. W. Hall | Michael J.W. Hall, Erika Andersson and Thomas Brougham | Maximum observable correlation for a bipartite quantum system | Revtex, no figures | Phys. Rev. A 74 (2006) 062308 | 10.1103/PhysRevA.74.062308 | null | quant-ph | null | The maximum observable correlation between the two components of a bipartite
quantum system is a property of the joint density operator, and is achieved by
making particular measurements on the respective components. For pure states it
corresponds to making measurements diagonal in a corresponding Schmidt basis.
More generally, it is shown that the maximum correlation may be characterised
in terms of a `correlation basis' for the joint density operator, which defines
the corresponding (nondegenerate) optimal measurements. The maximum coincidence
rate for spin measurements on two-qubit systems is determined to be (1+s)/2,
where s is the spectral norm of the spin correlation matrix, and upper bounds
are obtained for n-valued measurements on general bipartite systems. It is
shown that the maximum coincidence rate is never greater than the computable
cross norm measure of entanglement, and a much tighter upper bound is
conjectured. Connections with optimal state discrimination and entanglement
bounds are briefly discussed.
| [
{
"version": "v1",
"created": "Mon, 11 Sep 2006 09:30:54 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Hall",
"Michael J. W.",
""
],
[
"Andersson",
"Erika",
""
],
[
"Brougham",
"Thomas",
""
]
]
|
quant-ph/0609077 | David Hallwood | David W. Hallwood, Keith Burnett, Jacob Dunningham | An investigation into why macroscopic systems behave classically | 23 preprint pages, 12 figures | J. Mod. Opt. 54, 2129 (2007) | null | null | quant-ph | null | We study why it is quite so hard to make a superposition of superfluid flows
in a Bose-Einstein condensate. To do this we initially investigate the quantum
states of $N$ atoms trapped in a 1D ring with a barrier at one position and a
phase applied around it. We show how macroscopic superpositions can in
principle be produced and investigate factors which affect the superposition.
We then use the Bose-Hubbard model to study an array of Bose-Einstein
condensates trapped in optical potentials and coupled to one another to form a
ring. We derive analytic expressions for the quality of the superposition for
this system, which agrees well with direct diagonalisation of the Hamiltonian
for relatively small numbers of atoms. We show that for macroscopic
superpositions to be realised there are essentially three straightforward
requirements, other than an absence of decoherence, which become harder to
achieve as the system size increases. Firstly, the energies of the two distinct
superfluid states must be sufficiently close. Secondly, coupling between the
two states must be sufficiently strong, and thirdly, other states must be well
separated from those participating in the superposition.
| [
{
"version": "v1",
"created": "Mon, 11 Sep 2006 12:35:22 GMT"
},
{
"version": "v2",
"created": "Tue, 31 Oct 2006 17:31:43 GMT"
},
{
"version": "v3",
"created": "Thu, 2 Nov 2006 10:30:42 GMT"
},
{
"version": "v4",
"created": "Mon, 11 Dec 2006 15:50:19 GMT"
}
]
| 2011-09-05T00:00:00 | [
[
"Hallwood",
"David W.",
""
],
[
"Burnett",
"Keith",
""
],
[
"Dunningham",
"Jacob",
""
]
]
|
quant-ph/0609078 | Ho-Chih Lin | H.-C. Lin and A.J. Fisher | Configuration-Space Location of the Entanglement between Two Subsystems | RevTex, 12 pages, 9 figures (28 files). Modifications in response to
journal referees | Phys. Rev. A 75, 032330 (2007) | 10.1103/PhysRevA.75.032330 | null | quant-ph | null | In this paper we address the question: where in configuration space is the
entanglement between two particles located? We present a thought-experiment,
equally applicable to discrete or continuous-variable systems, in which one or
both parties makes a preliminary measurement of the state with only enough
resolution to determine whether or not the particle resides in a chosen region,
before attempting to make use of the entanglement. We argue that this provides
an operational answer to the question of how much entanglement was originally
located within the chosen region. We illustrate the approach in a spin system,
and also in a pair of coupled harmonic oscillators. Our approach is
particularly simple to implement for pure states, since in this case the
sub-ensemble in which the system is definitely located in the restricted region
after the measurement is also pure, and hence its entanglement can be simply
characterised by the entropy of the reduced density operators. For our spin
example we present results showing how the entanglement varies as a function of
the parameters of the initial state; for the continuous case, we find also how
it depends on the location and size of the chosen regions. Hence we show that
the distribution of entanglement is very different from the distribution of the
classical correlations.
| [
{
"version": "v1",
"created": "Mon, 11 Sep 2006 14:47:01 GMT"
},
{
"version": "v2",
"created": "Tue, 30 Jan 2007 14:45:42 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Lin",
"H. -C.",
""
],
[
"Fisher",
"A. J.",
""
]
]
|
quant-ph/0609079 | Johannes Kofler | Johannes Kofler, Caslav Brukner | Classical world arising out of quantum physics under the restriction of
coarse-grained measurements | 4 pages, 1 figure, second revised and published version | Phys. Rev. Lett. 99, 180403 (2007) | 10.1103/PhysRevLett.99.180403 | null | quant-ph | null | Conceptually different from the decoherence program, we present a novel
theoretical approach to macroscopic realism and classical physics within
quantum theory. It focuses on the limits of observability of quantum effects of
macroscopic objects, i.e., on the required precision of our measurement
apparatuses such that quantum phenomena can still be observed. First, we
demonstrate that for unrestricted measurement accuracy no classical description
is possible for arbitrarily large systems. Then we show for a certain time
evolution that under coarse-grained measurements not only macrorealism but even
the classical Newtonian laws emerge out of the Schroedinger equation and the
projection postulate.
| [
{
"version": "v1",
"created": "Mon, 11 Sep 2006 15:08:19 GMT"
},
{
"version": "v2",
"created": "Fri, 5 Jan 2007 16:52:56 GMT"
},
{
"version": "v3",
"created": "Fri, 2 Nov 2007 17:25:06 GMT"
}
]
| 2011-11-09T00:00:00 | [
[
"Kofler",
"Johannes",
""
],
[
"Brukner",
"Caslav",
""
]
]
|
quant-ph/0609080 | Marco Barbieri | M. Barbieri, G. Vallone, P. Mataloni and F. De Martini | Complete and Deterministic discrimination of polarization Bell state
assisted by momentum entanglement | 4 pages, v2, comments added | Phys. Rev. A 75, 042317 (2007) | 10.1103/PhysRevA.75.042317 | null | quant-ph | null | A complete and deterministic Bell state measurement was realized by a simple
linear optics experimental scheme which adopts 2-photon polarization-momentum
hyperentanglement. The scheme, which is based on the discrimination among the
single photon Bell states of the hyperentangled state, requires the adoption of
standard single photon detectors. The four polarization Bell states have been
measured with average fidelity $F=0.889\pm0.010$ by using the linear momentum
degree of freedom as the ancilla. The feasibility of the scheme has been
characterized as a function of the purity of momentum entanglement.
| [
{
"version": "v1",
"created": "Mon, 11 Sep 2006 16:06:44 GMT"
},
{
"version": "v2",
"created": "Tue, 19 Dec 2006 09:08:05 GMT"
}
]
| 2008-11-05T00:00:00 | [
[
"Barbieri",
"M.",
""
],
[
"Vallone",
"G.",
""
],
[
"Mataloni",
"P.",
""
],
[
"De Martini",
"F.",
""
]
]
|
quant-ph/0609081 | Xiang-Bin Wang | X. B. Wang | Secure and efficient decoy-state quantum key distribution with inexact
pulse intensities | null | Phys. Rev. A 75, 052301(2007) | 10.1103/PhysRevA.75.052301 | null | quant-ph | null | We present a general theorem for the efficient verification of the lower
bound of single-photon transmittance. We show how to do decoy-state quantum key
distribution efficiently with large random errors in the intensity control. In
our protocol, the linear terms of fluctuation disappear and only the quadratic
terms take effect. We then show the unconditional security of decoy-state
method with whatever error pattern in intensities of decoy pulses and signal
pulses provided that the intensity of each decoy pulse is less than $\mu$ and
the intensity of each signal pulse is larger than $\mu'$.
| [
{
"version": "v1",
"created": "Mon, 11 Sep 2006 16:39:13 GMT"
},
{
"version": "v2",
"created": "Mon, 18 Sep 2006 05:23:43 GMT"
},
{
"version": "v3",
"created": "Mon, 30 Oct 2006 17:28:36 GMT"
},
{
"version": "v4",
"created": "Mon, 6 Nov 2006 18:40:24 GMT"
},
{
"version": "v5",
"created": "Wed, 22 Nov 2006 17:27:30 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Wang",
"X. B.",
""
]
]
|
quant-ph/0609082 | Dmitry Gulevich | D. R. Gulevich and F. V. Kusmartsev | Magnetic relaxation of superconducting quantum dot: two-dimensional
false vacuum decay | null | Int. J. Mod. Phys. B 23, 4422 (2009) | null | null | quant-ph | null | Quantum tunneling of vortices has been found to be an important novel
phenomena for description of low temperature creep in high temperature
superconductors (HTSCs). We speculate that quantum tunneling may be also
exhibited in mesoscopic superconductors due to vortices trapped by the
Bean-Livingston barrier. The London approximation and method of images is used
to estimate the shape of the potential well in superconducting HTSC quantum
dot. To calculate the escape rate we use the instanton technique. We model the
vortex by a quantum particle tunneling from a two-dimensional ground state
under magnetic field applied in the transverse direction. The resulting decay
rates obtained by the instanton approach and conventional WKB are compared
revealing complete coincidence with each other.
| [
{
"version": "v1",
"created": "Mon, 11 Sep 2006 17:23:19 GMT"
}
]
| 2009-11-16T00:00:00 | [
[
"Gulevich",
"D. R.",
""
],
[
"Kusmartsev",
"F. V.",
""
]
]
|
quant-ph/0609083 | Feng Shuang | Feng Shuang, Herschel Rabitz, Mark Dykman | Foundations for Cooperating with Control Noise in the Manipulation of
Quantum Dynamics | submitted to Phys. Rev. E | null | 10.1103/PhysRevE.75.021103 | null | quant-ph | null | This paper develops the theoretical foundations for the ability of a control
field to cooperate with noise in the manipulation of quantum dynamics. The
noise enters as run-to-run variations in the control amplitudes, phases and
frequencies with the observation being an ensemble average over many runs as is
commonly done in the laboratory. Weak field perturbation theory is developed to
show that noise in the amplitude and frequency components of the control field
can enhance the process of population transfer in a multilevel ladder system.
The analytical results in this paper support the point that under suitable
conditions an optimal field can cooperate with noise to improve the control
outcome.
| [
{
"version": "v1",
"created": "Mon, 11 Sep 2006 18:28:51 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Shuang",
"Feng",
""
],
[
"Rabitz",
"Herschel",
""
],
[
"Dykman",
"Mark",
""
]
]
|
quant-ph/0609084 | Feng Shuang | Feng Shuang, Alexander Pechen, Tak-San Ho and Herschel Rabitz | Observation-assisted optimal control of quantum dynamics | null | J. Chem. Phys. 126, 134303 (2007) | 10.1063/1.2711806 | null | quant-ph | null | This paper explores the utility of instantaneous and continuous observations
in the optimal control of quantum dynamics. Simulations of the processes are
performed on several multilevel quantum systems with the goal of population
transfer. Optimal control fields are shown to be capable of cooperating or
fighting with observations to achieve a good yield, and the nature of the
observations may be optimized to more effectively control the quantum dynamics.
Quantum observations also can break dynamical symmetries to increase the
controllability of a quantum system. The quantum Zeno and anti-Zeno effects
induced by observations are the key operating principles in these processes.
The results indicate that quantum observations can be effective tools in the
control of quantum dynamics.
| [
{
"version": "v1",
"created": "Mon, 11 Sep 2006 18:43:32 GMT"
},
{
"version": "v2",
"created": "Thu, 31 May 2007 01:28:59 GMT"
}
]
| 2007-06-13T00:00:00 | [
[
"Shuang",
"Feng",
""
],
[
"Pechen",
"Alexander",
""
],
[
"Ho",
"Tak-San",
""
],
[
"Rabitz",
"Herschel",
""
]
]
|
quant-ph/0609085 | Dominic Horsman | Dominic Horsman and Vlatko Vedral | Developing the Deutsch-Hayden approach to quantum mechanics | 14 pages. Added section on entanglement swapping | New Journal of Physics 9 No. 5 135 (2007) | 10.1088/1367-2630/9/5/135 | null | quant-ph | null | The formalism of Deutsch and Hayden is a useful tool for describing quantum
mechanics explicitly as local and unitary, and therefore quantum information
theory as concerning a "flow" of information between systems. In this paper we
show that these physical descriptions of flow are unique, and develop the
approach further to include the measurement interaction and mixed states. We
then give an analysis of entanglement swapping in this approach, showing that
it does not in fact contain non-local effects or some form of superluminal
signalling.
| [
{
"version": "v1",
"created": "Tue, 12 Sep 2006 17:10:22 GMT"
},
{
"version": "v2",
"created": "Thu, 23 Nov 2006 11:11:10 GMT"
},
{
"version": "v3",
"created": "Fri, 2 Nov 2007 13:34:28 GMT"
}
]
| 2023-04-21T00:00:00 | [
[
"Horsman",
"Dominic",
""
],
[
"Vedral",
"Vlatko",
""
]
]
|
quant-ph/0609086 | Margaret Hawton | Margaret Hawton | Photon wave function and position eigenvectors | email: [email protected], All comments welcomed | null | null | null | quant-ph | null | One and two photon wave functions are obtained by projection onto a basis of
simultaneous eigenvectors of the position and number operators.
| [
{
"version": "v1",
"created": "Mon, 11 Sep 2006 19:49:59 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Hawton",
"Margaret",
""
]
]
|
quant-ph/0609087 | Xiao-qiang Xi | Xiao-Qiang Xi, W. M. Liu | An Important Properties of Entanglement: Pairwise Entanglement can Only
be Transferred by Entangled Pair | 4 pages, 5 figures | null | 10.1088/1009-1963/16/7/009 | null | quant-ph | null | Basing on the calculation of all the pairwise entanglement in the $n$ ($n
\leq 6$)-qubit Heisenberg XX open chain with system impurity, we find an
important result: pairwise entanglement can only be transferred through
entangled pair. The non-nearest pairwise entanglement will has the possibility
to exist as long as there has even number qubit in their middle. This point
means that we can get longer distance entanglement in solid system.
| [
{
"version": "v1",
"created": "Tue, 12 Sep 2006 02:21:57 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Xi",
"Xiao-Qiang",
""
],
[
"Liu",
"W. M.",
""
]
]
|
quant-ph/0609088 | Kia Manouchehri | K. Manouchehri and J. B. Wang | Quantum Walks in an array of Quantum Dots | 21 pages, 9 figures, to appear in J. Phys. A; changed title and
content, the new scheme is more scalable and experimentally viable | null | null | null | quant-ph | null | Quantum random walks are shown to have non-intuitive dynamics, which makes
them an attractive area of study for devising quantum algorithms for well-known
classical problems as well as those arising in the field of quantum computing.
In this work we propose a novel scheme for the physical implementation of a
discrete-time quantum random walk using laser excitations of the electronic
states of an array of quantum dots. These dots represent the discrete nodes of
the walk, while transitions between the energy levels inside each dot
correspond to the required coin operation and stimulated Raman adiabatic
passage (STIRAP) processes are employed to induce the steps of the walk. The
quantum dot design is tailored in such a way as to enable selective coupling of
the energy levels. Our simulation results show a close agreement with the ideal
quantum walk distribution as well as modest robustness towards noise
disturbance.
| [
{
"version": "v1",
"created": "Tue, 12 Sep 2006 15:02:31 GMT"
},
{
"version": "v2",
"created": "Tue, 11 Dec 2007 08:18:15 GMT"
}
]
| 2007-12-11T00:00:00 | [
[
"Manouchehri",
"K.",
""
],
[
"Wang",
"J. B.",
""
]
]
|
quant-ph/0609089 | Ramazan Sever | Ozlem Yesiltas and Ramazan Sever | Exact solutions of Schrodinger equation for PT-/non-PT-symmetric and
non-Hermitian Exponential Type Potentials with the position-dependent
effective mass | 18 pages | null | null | null | quant-ph | null | Exact solutions of Schrodinger equation for PT-/non-PT-symmetric and
non-Hermitian Morse and Poschl-Teller potentials are obtained with the
position-dependent effective mass by applying a point canonical transformation
method. Three kinds of mass distributions are used in order to construct
exactly solvable target potentials and obtain energy spectrum and corresponding
wave functions.
| [
{
"version": "v1",
"created": "Tue, 12 Sep 2006 07:00:48 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Yesiltas",
"Ozlem",
""
],
[
"Sever",
"Ramazan",
""
]
]
|
quant-ph/0609090 | Cyril Branciard | Cyril Branciard, Nicolas Gisin, Norbert Lutkenhaus, Valerio Scarani | Zero-Error Attacks and Detection Statistics in the Coherent One-Way
Protocol for Quantum Cryptography | null | Quant. Inf. Comput. 7, 639 (2007) | null | null | quant-ph | null | This is a study of the security of the Coherent One-Way (COW) protocol for
quantum cryptography, proposed recently as a simple and fast experimental
scheme. In the zero-error regime, the eavesdropper Eve can only take advantage
of the losses in the transmission. We consider new attacks, based on
unambiguous state discrimination, which perform better than the basic
beam-splitting attack, but which can be detected by a careful analysis of the
detection statistics. These results stress the importance of testing several
statistical parameters in order to achieve higher rates of secret bits.
| [
{
"version": "v1",
"created": "Tue, 12 Sep 2006 14:17:56 GMT"
}
]
| 2008-02-05T00:00:00 | [
[
"Branciard",
"Cyril",
""
],
[
"Gisin",
"Nicolas",
""
],
[
"Lutkenhaus",
"Norbert",
""
],
[
"Scarani",
"Valerio",
""
]
]
|
quant-ph/0609091 | Ren Xijun | Y.-J. Han, X. J. Ren, Y. C. Wu, G.-C. Guo | Partial transposition on bi-partite system | null | null | null | null | quant-ph | null | Many of the properties of the partial transposition are not clear so far.
Here the number of the negative eigenvalues of K(T)(the partial transposition
of K) is considered carefully when K is a two-partite state. There are strong
evidences to show that the number of negative eigenvalues of K(T) is N(N-1)/2
at most when K is a state in Hilbert space N*N. For the special case, 2*2
system(two qubits), we use this result to give a partial proof of the
conjecture sqrt(K(T))(T)>=0. We find that this conjecture is strongly connected
with the entanglement of the state corresponding to the negative eigenvalue of
K(T) or the negative entropy of K.
| [
{
"version": "v1",
"created": "Tue, 12 Sep 2006 11:13:12 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Han",
"Y. -J.",
""
],
[
"Ren",
"X. J.",
""
],
[
"Wu",
"Y. C.",
""
],
[
"Guo",
"G. -C.",
""
]
]
|
quant-ph/0609092 | Zeqian Chen | Zeqian Chen | Wave-particle duality and `bipartite' wave functions for a single
particle | 3 pages | null | null | null | quant-ph | null | It is shown that `bipartite' wave functions can present a mathematical
formalism of quantum theory for a single particle, in which the associated
Schr\"{o}dinger's wave functions correspond to those `bipartite' wave functions
of product forms. This extension of Schr\"{o}dinger's form establishes a
mathematical expression of wave-particle duality and that von Neumann's entropy
is a quantitative measure of complementarity between wave-like and
particle-like behaviors. In particular, this formalism suggests that collapses
of Schr\"{o}dinger's wave functions can be regarded as the simultaneous
transition of the particle from many levels to one. Our results shed
considerable light on the basis of quantum mechanics, including quantum
measurement.
| [
{
"version": "v1",
"created": "Tue, 12 Sep 2006 13:17:58 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Chen",
"Zeqian",
""
]
]
|
quant-ph/0609093 | Wen-Ge Wang | Wen-ge Wang | Entanglement and Disentanglement, Probabilistic Interpretation of
Statevectors, and Transformation between Intrinsic Frames of Reference | 4 pages. All types of comments are welcome | null | null | null | quant-ph | null | We study a quantum theory based on two assumptions:
In the intrinsic frame of reference of an isolated, macroscopic system,
(i) the system has no global motion and is not entangled with any other
system, (ii) time evolution of statevectors of systems outside the system
satisfy Schr\"{o}dinger equation.
A process of collision-type interaction between a microscopic system and a
macroscopic system is studied in an auxiliary frame of reference.
In transforming the statevector of the two systems obtained in the auxiliary
frame of reference to the intrinsic frame of reference of the macroscopic
system, the above first assumption requires a discontinuous change of the
statevector. A probabilistic interpretation is given to the statevector for the
discontinuous change. For the microscopic system, the density matrix given in
the theory here is equal to the reduced density matrix given in the usual
quantum mechanics.
| [
{
"version": "v1",
"created": "Tue, 12 Sep 2006 13:26:46 GMT"
}
]
| 2016-09-08T00:00:00 | [
[
"Wang",
"Wen-ge",
""
]
]
|
quant-ph/0609094 | Marcos Curty | Marcos Curty, Lucy Liuxuan Zhang, Hoi-Kwong Lo, Norbert L\"utkenhaus | Sequential attacks against differential-phase-shift quantum key
distribution with weak coherent states | 13 pages, 11 figures | QIC Vol 7,p. 665-688 (2007) | null | null | quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We investigate limitations imposed by sequential attacks on the performance
of differential-phase-shift quantum key distribution protocols that use pulsed
coherent light. In particular, we analyze two sequential attacks based on
unambiguous state discrimination and minimum error discrimination,
respectively, of the signal states emitted by the source. Sequential attacks
represent a special type of intercept-resend attacks and, therefore, they do
not allow the distribution of a secret key.
| [
{
"version": "v1",
"created": "Tue, 12 Sep 2006 13:39:06 GMT"
},
{
"version": "v2",
"created": "Mon, 19 Aug 2013 21:00:35 GMT"
}
]
| 2013-08-21T00:00:00 | [
[
"Curty",
"Marcos",
""
],
[
"Zhang",
"Lucy Liuxuan",
""
],
[
"Lo",
"Hoi-Kwong",
""
],
[
"Lütkenhaus",
"Norbert",
""
]
]
|
quant-ph/0609095 | Timothy Jarrett | Timothy C. Jarrett, Alexandra Olaya-Castro and Neil F. Johnson | Optical signatures of quantum phase transitions in a light-matter system | 4 pages, 4 figures | null | 10.1209/0295-5075/77/34001 | null | quant-ph cond-mat.mes-hall | null | Information about quantum phase transitions in conventional condensed matter
systems, must be sought by probing the matter system itself. By contrast, we
show that mixed matter-light systems offer a distinct advantage in that the
photon field carries clear signatures of the associated quantum critical
phenomena. Having derived an accurate, size-consistent Hamiltonian for the
photonic field in the well-known Dicke model, we predict striking behavior of
the optical squeezing and photon statistics near the phase transition. The
corresponding dynamics resemble those of a degenerate parametric amplifier. Our
findings boost the motivation for exploring exotic quantum phase transition
phenomena in atom-cavity, nanostructure-cavity, and
nanostructure-photonic-band-gap systems.
| [
{
"version": "v1",
"created": "Tue, 12 Sep 2006 16:23:58 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Jarrett",
"Timothy C.",
""
],
[
"Olaya-Castro",
"Alexandra",
""
],
[
"Johnson",
"Neil F.",
""
]
]
|
quant-ph/0609096 | Andreas Fring | Carla Figueira de Morisson Faria and Andreas Fring | Non-Hermitian Hamiltonians with real eigenvalues coupled to electric
fields: from the time-independent to the time dependent quantum mechanical
formulation | 14 pages, 3 figures, to appear in Laser Physics, minor typos
corrected | Laser Physics 17 (2007) 424-437 | 10.1134/S1054660X07040196 | null | quant-ph | null | We provide a reviewlike introduction into the quantum mechanical formalism
related to non-Hermitian Hamiltonian systems with real eigenvalues. Starting
with the time-independent framework we explain how to determine an appropriate
domain of a non-Hermitian Hamiltonian and pay particular attention to the role
played by PT-symmetry and pseudo-Hermiticity. We discuss the time-evolution of
such systems having in particular the question in mind of how to couple
consistently an electric field to pseudo-Hermitian Hamiltonians. We illustrate
the general formalism with three explicit examples: i) the generalized Swanson
Hamiltonians, which constitute non-Hermitian extensions of anharmonic
oscillators, ii) the spiked harmonic oscillator, which exhibits explicit
supersymmetry and iii) the -x^4-potential, which serves as a toy model for the
quantum field theoretical phi^4-theory.
| [
{
"version": "v1",
"created": "Tue, 12 Sep 2006 18:28:59 GMT"
},
{
"version": "v2",
"created": "Mon, 15 Jan 2007 16:07:14 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Faria",
"Carla Figueira de Morisson",
""
],
[
"Fring",
"Andreas",
""
]
]
|
quant-ph/0609097 | Alexander Pechen | Alexander Pechen and Herschel Rabitz | Teaching the Environment to Control Quantum Systems | null | Phys. Rev. A 73, 062102 (2006) | 10.1103/PhysRevA.73.062102 | null | quant-ph | null | A non-equilibrium, generally time-dependent, environment whose form is
deduced by optimal learning control is shown to provide a means for incoherent
manipulation of quantum systems. Incoherent control by the environment (ICE)
can serve to steer a system from an initial state to a target state, either
mixed or in some cases pure, by exploiting dissipative dynamics. Implementing
ICE with either incoherent radiation or a gas as the control is explicitly
considered, and the environmental control is characterized by its distribution
function. Simulated learning control experiments are performed with simple
illustrations to find the shape of the optimal non-equilibrium distribution
function that best affects the posed dynamical objectives.
| [
{
"version": "v1",
"created": "Tue, 12 Sep 2006 22:55:09 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Pechen",
"Alexander",
""
],
[
"Rabitz",
"Herschel",
""
]
]
|
quant-ph/0609098 | Fabio Franchini | F. Franchini, A. R. Its, B.-Q. Jin and V. E. Korepin | Ellipses of Constant Entropy in the XY Spin Chain | Revised Version, 20 pages, 8 figures, 1 table | J. Phys. A: Math. Theor. 40 (2007) 8467-8478 | 10.1088/1751-8113/40/29/019 | null | quant-ph cond-mat.stat-mech hep-th math-ph math.MP | null | Entanglement in the ground state of the XY model on the infinite chain can be
measured by the von Neumann entropy of a block of neighboring spins. We study a
double scaling limit: the size of the block is much larger then 1 but much
smaller then the length of the whole chain. The entropy of the block has an
asymptotic limit. We study this limiting entropy as a function of the
anisotropy and of the magnetic field. We identify its minima at product states
and its divergencies at the quantum phase transitions. We find that the curves
of constant entropy are ellipses and hyperbolas and that they all meet at one
point (essential critical point). Depending on the approach to the essential
critical point the entropy can take any value between 0 and infinity. In the
vicinity of this point small changes in the parameters cause large change of
the entropy.
| [
{
"version": "v1",
"created": "Wed, 13 Sep 2006 04:47:49 GMT"
},
{
"version": "v2",
"created": "Wed, 27 Sep 2006 16:46:43 GMT"
},
{
"version": "v3",
"created": "Wed, 31 Jan 2007 21:02:18 GMT"
},
{
"version": "v4",
"created": "Tue, 3 Jul 2007 13:43:08 GMT"
},
{
"version": "v5",
"created": "Sun, 8 Jul 2007 00:11:39 GMT"
}
]
| 2012-01-31T00:00:00 | [
[
"Franchini",
"F.",
""
],
[
"Its",
"A. R.",
""
],
[
"Jin",
"B. -Q.",
""
],
[
"Korepin",
"V. E.",
""
]
]
|
quant-ph/0609099 | Ramon Lapiedra | Ramon Lapiedra | Joint reality and Bell inequalities for consecutive measurements | 7 pages, no figures | Europhysical Letters, 75 (2), 202 (2006) | 10.1209/epl/i2005-10600-6 | null | quant-ph | null | Some new Bell inequalities for consecutive measurements are deduced under
joint realism assumption, using some perfect correlation property. No locality
condition is needed. When the measured system is a macroscopic system, joint
realism assumption substitutes the non-invasive hypothesis advantageously,
provided that the system satisfies the perfect correlation property. The new
inequalities are violated quantically. This violation can be expected to be
more severe than in the case of precedent temporal Bell inequalities. Some
microscopic and mesoscopic situations, in which the new inequalities could be
tested, are roughly considered.
| [
{
"version": "v1",
"created": "Wed, 13 Sep 2006 09:31:53 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Lapiedra",
"Ramon",
""
]
]
|
quant-ph/0609100 | Francesco de Martini | Marco Caminati, Francesco De Martini, Riccardo Perris, Fabio
Sciarrino, Veronica Secondi | Entanglement, EPR correlations and mesoscopic quantum superposition by
the high-gain quantum injected parametric amplification | 9 pages, 5 figures | Phys. Rev. A 74, 062304 (2006) | 10.1103/PhysRevA.74.062304 | null | quant-ph | null | We investigate the multiparticle quantum superposition and the persistence of
multipartite entanglement of the quantum superposition generated by the quantum
injected high-gain optical parametric amplification of a single photon. The
physical configuration based on the optimal universal quantum cloning has been
adopted to investigate how the entanglement and the quantum coherence of the
system persists for large values of the nonlinear parametric gain g.
| [
{
"version": "v1",
"created": "Wed, 13 Sep 2006 11:34:34 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Caminati",
"Marco",
""
],
[
"De Martini",
"Francesco",
""
],
[
"Perris",
"Riccardo",
""
],
[
"Sciarrino",
"Fabio",
""
],
[
"Secondi",
"Veronica",
""
]
]
|
quant-ph/0609101 | Chuanwei Zhang | Chuanwei Zhang, V.W. Scarola, Sumanta Tewari and S. Das Sarma | Anyonic Braiding in Optical Lattices | 22 pages, 5 figures, published version | Proc. Natl. Acad. Sci. USA 104, 18415 (2007) | 10.1073/pnas.0709075104 | null | quant-ph cond-mat.other cond-mat.soft | null | Topological quantum states of matter, both Abelian and non-Abelian, are
characterized by excitations whose wavefunctions undergo non-trivial
statistical transformations as one excitation is moved (braided) around
another. Topological quantum computation proposes to use the topological
protection and the braiding statistics of a non-Abelian topological state to
perform quantum computation. The enormous technological prospect of topological
quantum computation provides new motivation for experimentally observing a
topological state. Here we explicitly work out a realistic experimental scheme
to create and braid the Abelian topological excitations in the Kitaev model
built on a tunable robust system, a cold atom optical lattice. We also
demonstrate how to detect the key feature of these excitations, their braiding
statistics. Observation of this statistics would directly establish the
existence of anyons, quantum particles which are neither fermions nor bosons.
In addition to establishing topological matter, the experimental scheme we
develop here can also be adapted to a non-Abelian topological state, supported
by the same Kitaev model but in a different parameter regime, to eventually
build topologically protected quantum gates.
| [
{
"version": "v1",
"created": "Wed, 13 Sep 2006 14:55:43 GMT"
},
{
"version": "v2",
"created": "Wed, 13 Sep 2006 21:26:28 GMT"
},
{
"version": "v3",
"created": "Thu, 18 Oct 2007 14:37:31 GMT"
},
{
"version": "v4",
"created": "Tue, 27 Nov 2007 20:29:50 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Zhang",
"Chuanwei",
""
],
[
"Scarola",
"V. W.",
""
],
[
"Tewari",
"Sumanta",
""
],
[
"Sarma",
"S. Das",
""
]
]
|
quant-ph/0609102 | Damian Markham | Damian Markham, Akimasa Miyake and Shashank Virmani | Entanglement and local information access for graph states | 8 pages, 4 figures, to appear in the special issue of New J. Phys. on
measurement-based quantum information processing | New J. Phys. 9, 194 (2007) | 10.1088/1367-2630/9/6/194 | null | quant-ph | null | We exactly evaluate a number of multipartite entanglement measures for a
class of graph states, including d-dimensional cluster states (d = 1,2,3), the
Greenberger-Horne-Zeilinger states, and some related mixed states. The
entanglement measures that we consider are continuous, `distance from separable
states' measures, including the relative entropy, the so-called geometric
measure, and robustness of entanglement. We also show that for our class of
graph states these entanglement values give an operational interpretation as
the maximal number of graph states distinguishable by local operations and
classical communication (LOCC), as well as supplying a tight bound on the fixed
letter classical capacity under LOCC decoding.
| [
{
"version": "v1",
"created": "Wed, 13 Sep 2006 17:27:20 GMT"
},
{
"version": "v2",
"created": "Wed, 28 Mar 2007 14:22:15 GMT"
},
{
"version": "v3",
"created": "Wed, 4 Jul 2007 08:04:10 GMT"
}
]
| 2007-07-10T00:00:00 | [
[
"Markham",
"Damian",
""
],
[
"Miyake",
"Akimasa",
""
],
[
"Virmani",
"Shashank",
""
]
]
|
quant-ph/0609103 | Pablo Barberis-Blostein | P. Barberis-Blostein and M. Bienert | Opacity of electromagnetically induced transparency for quantum
fluctuations | null | Phys. Rev. Lett. 98, 033602 (2007) | 10.1103/PhysRevLett.98.033602 | null | quant-ph | null | We analyze the propagation of a pair of quantized fields inside a medium of
three-level atoms in $\Lambda$ configuration. We calculate the stationary
quadrature noise spectrum of the field after propagating through the medium, in
the case where the probe field is in a squeezed state and the atoms show
electromagnetically induced transparency (EIT). We find an oscillatory transfer
of the initial quantum properties between the probe and pump fields which is
most strongly pronounced when both fields have comparable Rabi frequencies.
This implies that the quantum state measured after propagation can be
completely different from the initial state, even though the mean values of the
field are unaltered.
| [
{
"version": "v1",
"created": "Thu, 14 Sep 2006 00:38:22 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Barberis-Blostein",
"P.",
""
],
[
"Bienert",
"M.",
""
]
]
|
quant-ph/0609104 | Dmitry Kamenev | D. I. Kamenev, G. P. Berman, V. I. Tsifrinovich | Influence of qubit displacements on quantum logic operations in a
silicon-based quantum computer with constant interaction | null | null | 10.1103/PhysRevA.74.042337 | null | quant-ph | null | The errors caused by qubit displacements from their prescribed locations in
an ensemble of spin chains are estimated analytically and calculated
numerically for a quantum computer based on phosphorus donors in silicon. We
show that it is possible to polarize (initialize) the nuclear spins even with
displaced qubits by using Controlled NOT gates between the electron and nuclear
spins of the same phosphorus atom. However, a Controlled NOT gate between the
displaced electron spins is implemented with large error because of the
exponential dependence of exchange interaction constant on the distance between
the qubits. If quantum computation is implemented on an ensemble of many spin
chains, the errors can be small if the number of chains with displaced qubits
is small.
| [
{
"version": "v1",
"created": "Thu, 14 Sep 2006 01:42:38 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Kamenev",
"D. I.",
""
],
[
"Berman",
"G. P.",
""
],
[
"Tsifrinovich",
"V. I.",
""
]
]
|
quant-ph/0609105 | Francesco de Martini | Fabio Sciarrino and Francesco De Martini | Implementation of optimal phase-covariant cloning machines | 7 pages, 3 figures | Phys. Rev. A 76, 012330 (2007) | 10.1103/PhysRevA.76.012330 | null | quant-ph | null | The optimal phase covariant cloning machine (PQCM) broadcasts the information
associated to an input qubit into a multi-qubit systems, exploiting a partial
a-priori knowledge of the input state. This additional a priori information
leads to a higher fidelity than for the universal cloning. The present article
first analyzes different experimental schemes to implement the 1->3 PQCM. The
method is then generalized to any 1->M machine for odd value of M by a
theoretical approach based on the general angular momentum formalism. Finally
different experimental schemes based either on linear or non-linear methods and
valid for single photon polarization encoded qubits are discussed.
| [
{
"version": "v1",
"created": "Thu, 14 Sep 2006 08:15:25 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Sciarrino",
"Fabio",
""
],
[
"De Martini",
"Francesco",
""
]
]
|
quant-ph/0609106 | Alejandro Romanelli | Alejandro Romanelli | Quantum games via search algorithms | 4 pages, 3 figures | Physica A 379, 545 (2007) | 10.1016/j.physa.2007.02.029 | null | quant-ph | null | We build new quantum games, similar to the spin flip game, where as a novelty
the players perform measurements on a quantum system associated to a continuous
time search algorithm. The measurements collapse the wave function into one of
the two possible states. These games are characterized by a continuous space of
strategies and the selection of a particular strategy is determined by the
moments when the players measure.
| [
{
"version": "v1",
"created": "Thu, 14 Sep 2006 15:49:53 GMT"
},
{
"version": "v2",
"created": "Thu, 15 Feb 2007 12:19:23 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Romanelli",
"Alejandro",
""
]
]
|
quant-ph/0609107 | Marie-No\"elle C\'el\'erier | Marie-Noelle Celerier and Laurent Nottale (LUTH, Observatoire de
Paris-Meudon) | The Pauli equation in scale relativity | 22 pages, 2 figures, accepted for publication in J. Phys. A: Math. &
Gen | J.Phys.A39:12565-12585,2006 | 10.1088/0305-4470/39/40/020 | null | quant-ph | null | In standard quantum mechanics, it is not possible to directly extend the
Schrodinger equation to spinors, so the Pauli equation must be derived from the
Dirac equation by taking its non-relativistic limit. Hence, it predicts the
existence of an intrinsic magnetic moment for the electron and gives its
correct value. In the scale relativity framework, the Schrodinger, Klein-Gordon
and Dirac equations have been derived from first principles as geodesics
equations of a non-differentiable and continuous spacetime. Since such a
generalized geometry implies the occurence of new discrete symmetry breakings,
this has led us to write Dirac bi-spinors in the form of bi-quaternions
(complex quaternions). In the present work, we show that, in scale relativity
also, the correct Pauli equation can only be obtained from a non-relativistic
limit of the relativistic geodesics equation (which, after integration, becomes
the Dirac equation) and not from the non-relativistic formalism (that involves
symmetry breakings in a fractal 3-space). The same degeneracy procedure, when
it is applied to the bi-quaternionic 4-velocity used to derive the Dirac
equation, naturally yields a Pauli-type quaternionic 3-velocity. It therefore
corroborates the relevance of the scale relativity approach for the building
from first principles of the quantum postulates and of the quantum tools. This
also reinforces the relativistic and fundamentally quantum nature of spin,
which we attribute in scale relativity to the non-differentiability of the
quantum spacetime geometry (and not only of the quantum space). We conclude by
performing numerical simulations of spinor geodesics, that allow one to gain a
physical geometric picture of the nature of spin.
| [
{
"version": "v1",
"created": "Thu, 14 Sep 2006 09:57:59 GMT"
}
]
| 2011-07-13T00:00:00 | [
[
"Celerier",
"Marie-Noelle",
"",
"LUTH, Observatoire de\n Paris-Meudon"
],
[
"Nottale",
"Laurent",
"",
"LUTH, Observatoire de\n Paris-Meudon"
]
]
|
quant-ph/0609108 | Richard A. Mould | Richard A. Mould | Foundation q-rules | 22 pages, 0 figures | null | null | null | quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | The q-rules are three auxiliary rules that guide the application of
Schrodinger's equation. They are a set of instructions that describe how
stochastic choices cause the wave to collapse and "start over" with new
boundary conditions.
| [
{
"version": "v1",
"created": "Thu, 14 Sep 2006 14:39:53 GMT"
},
{
"version": "v2",
"created": "Wed, 9 Jan 2008 16:51:29 GMT"
},
{
"version": "v3",
"created": "Tue, 21 Oct 2008 16:46:19 GMT"
},
{
"version": "v4",
"created": "Fri, 12 Dec 2008 16:27:25 GMT"
},
{
"version": "v5",
"created": "Thu, 10 Nov 2011 15:58:36 GMT"
}
]
| 2011-11-11T00:00:00 | [
[
"Mould",
"Richard A.",
""
]
]
|
quant-ph/0609109 | Lee Smolin | Lee Smolin | Could quantum mechanics be an approximation to another theory? | 10 pages, no figures | null | null | null | quant-ph gr-qc hep-th | null | We consider the hypothesis that quantum mechanics is an approximation to
another, cosmological theory, accurate only for the description of subsystems
of the universe. Quantum theory is then to be derived from the cosmological
theory by averaging over variables which are not internal to the subsystem,
which may be considered non-local hidden variables. We find conditions for
arriving at quantum mechanics through such a procedure. The key lesson is that
the effect of the coupling to the external degrees of freedom introduces noise
into the evolution of the system degrees of freedom, while preserving a notion
of averaged conserved energy and time reversal invariance.
These conditions imply that the effective description of the subsystem is
Nelson's stochastic formulation of quantum theory. We show that Nelson's
formulation is not, by itself, a classical stochastic theory as the conserved
averaged energy is not a linear function of the probability density. We also
investigate an argument of Wallstrom posed against the equivalence of Nelson's
stochastic mechanics and quantum mechanics and show that, at least for a simple
case, it is in error.
| [
{
"version": "v1",
"created": "Thu, 14 Sep 2006 14:43:09 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Smolin",
"Lee",
""
]
]
|
quant-ph/0609110 | Andrew M. Childs | Andrew M. Childs, Aram W. Harrow, Pawel Wocjan | Weak Fourier-Schur sampling, the hidden subgroup problem, and the
quantum collision problem | 21 pages | Proc. 24th Symposium on Theoretical Aspects of Computer Science
(STACS 2007), Lecture Notes in Computer Science 4393, pp. 598-609 | 10.1007/978-3-540-70918-3_51 | null | quant-ph | null | Schur duality decomposes many copies of a quantum state into subspaces
labeled by partitions, a decomposition with applications throughout quantum
information theory. Here we consider applying Schur duality to the problem of
distinguishing coset states in the standard approach to the hidden subgroup
problem. We observe that simply measuring the partition (a procedure we call
weak Schur sampling) provides very little information about the hidden
subgroup. Furthermore, we show that under quite general assumptions, even a
combination of weak Fourier sampling and weak Schur sampling fails to identify
the hidden subgroup. We also prove tight bounds on how many coset states are
required to solve the hidden subgroup problem by weak Schur sampling, and we
relate this question to a quantum version of the collision problem.
| [
{
"version": "v1",
"created": "Thu, 14 Sep 2006 20:19:30 GMT"
}
]
| 2007-06-13T00:00:00 | [
[
"Childs",
"Andrew M.",
""
],
[
"Harrow",
"Aram W.",
""
],
[
"Wocjan",
"Pawel",
""
]
]
|
quant-ph/0609111 | David Hayes | David Hayes, Paul Julienne, Ivan Deutsch | Quantum logic via the exchange blockade in ultracold collisions | null | null | 10.1103/PhysRevLett.98.070501 | null | quant-ph | null | A nuclear spin can act as a quantum switch that turns on or off ultracold
collisions between atoms even when there is neither interaction between nuclear
spins nor between the nuclear and electron spins. This "exchange blockade" is a
new mechanism for implementing quantum logic gates that arises from the
symmetry of composite identical particles, rather than direct coupling between
qubits. We study the implementation of the entangling $\sqrt{\text{SWAP}}$ gate
based on this mechanism for a model system of two atoms with ground electron
configuration $^1S_0$, spin 1/2 nuclei, trapped in optical tweezers. We
evaluate a proof-of-principle protocol based on adiabatic evolution of a one
dimensional double Gaussian well, calculating fidelities of operation as a
function of interaction strength, gate time, and temperature.
| [
{
"version": "v1",
"created": "Thu, 14 Sep 2006 23:53:40 GMT"
},
{
"version": "v2",
"created": "Mon, 25 Sep 2006 16:20:30 GMT"
},
{
"version": "v3",
"created": "Mon, 4 Dec 2006 21:11:20 GMT"
}
]
| 2013-05-29T00:00:00 | [
[
"Hayes",
"David",
""
],
[
"Julienne",
"Paul",
""
],
[
"Deutsch",
"Ivan",
""
]
]
|
quant-ph/0609112 | Wen-Ge Wang | Wen-ge Wang, G.Casati, and Baowen Li | Stability of quantum motion in regular systems: a uniform semiclassical
approach | 5 pages, 4 figures, published version | Phys. Rev. E 75, 016201 (2007) | 10.1103/PhysRevE.75.016201 | null | quant-ph nlin.SI | null | We study the stability of quantum motion of classically regular systems in
presence of small perturbations. Onthe base of a uniform semiclassical theory
we derive the fidelity decay which displays a quite complexbehaviour, from
Gaussian to power law decay $t^{-\alpha}$ with $1 \le \alpha \le 2$.
Semiclassical estimates are given for the time scales separating the different
decaying regions and numerical results are presented which confirm our
theoretical predictions.
| [
{
"version": "v1",
"created": "Fri, 15 Sep 2006 03:00:53 GMT"
},
{
"version": "v2",
"created": "Fri, 19 Jan 2007 06:37:12 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Wang",
"Wen-ge",
""
],
[
"Casati",
"G.",
""
],
[
"Li",
"Baowen",
""
]
]
|
quant-ph/0609113 | C.M. Chandrashekar | C.M. Chandrashekar | Discrete time quantum walk model for single and entangled particles to
retain entanglement in coin space | 9 pages, 3 figures | null | null | null | quant-ph | null | In most widely discussed discrete time quantum walk model, after every
unitary shift operator, the particle evolves into the superposition of position
space and settles down in one of its basis states, loosing entanglement in the
coin space in the new position. The Hadamard operation is applied to let the
particle to evolve into the superposition in the coin space and the walk is
iterated. We present a model with a additional degree of freedom for the
unitary shift operator $U^{\prime}$. The unitary operator with additional
degree of freedom will evolve the quantum particle into superposition of
position space retaining the entanglement in coin space. This eliminates the
need for quantum coin toss (Hadamard operation) after every unitary
displacement operation as used in most widely studied version of the discrete
time quantum walk model. This construction is easily extended to a multiple
particle quantum walk and in this article we extend it for a pair of particles
in pure state entangled in coin degree of freedom by simultaneously subjecting
it to a pair of unitary displacement operators which were constructed for
single particle. We point out that unlike for single particle quantum walk,
upon measurement of its position after $N$ steps, the entangled particles are
found together with 1/2 probability and at different positions with 1/2
probability. This can act as an advantage in applications of the quantum walk.
A special case is also treated using a complex physical system such as, inter
species two-particle entangled Bose-Einstein condensate, as an example.
| [
{
"version": "v1",
"created": "Fri, 15 Sep 2006 04:40:22 GMT"
},
{
"version": "v2",
"created": "Tue, 26 Sep 2006 19:32:09 GMT"
},
{
"version": "v3",
"created": "Wed, 11 Oct 2006 00:22:10 GMT"
},
{
"version": "v4",
"created": "Sat, 28 Oct 2006 00:55:47 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Chandrashekar",
"C. M.",
""
]
]
|
quant-ph/0609114 | Nikolai Kolachevsky | N. Kolachevsky, M. Haas, U.D. Jentschura, M. Herrmann, P. Fendel, M.
Fischer, R. Holzwarth, Th. Udem, C.H. Keitel, T.W. Haensch | Photoionization Broadening of the 1S-2S Transition in a Beam of Atomic
Hydrogen | 10 pages, 5 figures | Phys. Rev. A 74, 052504 (2006) | 10.1103/PhysRevA.74.052504 | null | quant-ph | null | We consider the excitation dynamics of the two-photon \sts transition in a
beam of atomic hydrogen by 243 nm laser radiation. Specifically, we study the
impact of ionization damping on the transition line shape, caused by the
possibility of ionization of the 2S level by the same laser field. Using a
Monte-Carlo simulation, we calculate the line shape of the \sts transition for
the experimental geometry used in the two latest absolute frequency
measurements (M. Niering {\it et al.}, PRL 84, 5496 (2000) and M. Fischer {\it
et al.}, PRL 92, 230802 (2004)). The calculated line shift and line width are
in excellent agreement with the experimentally observed values. From this
comparison we can verify the values of the dynamic Stark shift coefficient for
the \sts transition for the first time on a level of 15%. We show that the
ionization modifies the velocity distribution of the metastable atoms, the line
shape of the \sts transition, and has an influence on the derivation of its
absolute frequency.
| [
{
"version": "v1",
"created": "Fri, 15 Sep 2006 08:40:21 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Kolachevsky",
"N.",
""
],
[
"Haas",
"M.",
""
],
[
"Jentschura",
"U. D.",
""
],
[
"Herrmann",
"M.",
""
],
[
"Fendel",
"P.",
""
],
[
"Fischer",
"M.",
""
],
[
"Holzwarth",
"R.",
""
],
[
"Udem",
"Th.",
""
],
[
"Keitel",
"C. H.",
""
],
[
"Haensch",
"T. W.",
""
]
]
|
quant-ph/0609115 | Pinaki Roy | T.Jana and P.Roy | Shape invariance approach to exact solutions of the Klein-Gordon
equation | null | null | 10.1016/j.physleta.2006.09.032 | null | quant-ph math-ph math.MP | null | Using the shape invariance property we obtain exact solutions of the
(1+1)dimensional Klein-Gordon equation for certain types of scalar and vector
potentials. We also discuss the possibility of obtaining real energy spectrum
with non-Hermitian interaction within this framework.
| [
{
"version": "v1",
"created": "Fri, 15 Sep 2006 08:42:59 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Jana",
"T.",
""
],
[
"Roy",
"P.",
""
]
]
|
quant-ph/0609116 | Akira Furusawa | Ken-ichiroh Yoshino, Takao Aoki, Akira Furusawa | Generation of continuous-wave broadband Einstein-Podolsky-Rosen beams
using periodically-poled lithium niobate waveguides | 4 pages, 3 figures | Appl. Phys. Lett. 90, 041111 (2007) | 10.1063/1.2437057 | null | quant-ph | null | Continuous-wave light beams with broadband Einstein-Podolsky-Rosen
correlation (Einstein-Podolsky-Rosen beams) are created with two independent
squeezed vacua generated by two periodically-poled lithium niobate waveguides
and a half beam splitter.
| [
{
"version": "v1",
"created": "Fri, 15 Sep 2006 11:50:51 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Yoshino",
"Ken-ichiroh",
""
],
[
"Aoki",
"Takao",
""
],
[
"Furusawa",
"Akira",
""
]
]
|
quant-ph/0609117 | Carlo A. Trugenberger | M.Cristina Diamantini and Carlo A. Trugenberger | Quantum Pattern Retrieval by Qubit Networks with Hebb Interactions | To appear in Physical Review Letters | null | 10.1103/PhysRevLett.97.130503 | null | quant-ph cond-mat.dis-nn cs.NE | null | Qubit networks with long-range interactions inspired by the Hebb rule can be
used as quantum associative memories. Starting from a uniform superposition,
the unitary evolution generated by these interactions drives the network
through a quantum phase transition at a critical computation time, after which
ferromagnetic order guarantees that a measurement retrieves the stored memory.
The maximum memory capacity p of these qubit networks is reached at a memory
density p/n=1.
| [
{
"version": "v1",
"created": "Fri, 15 Sep 2006 15:19:31 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Diamantini",
"M. Cristina",
""
],
[
"Trugenberger",
"Carlo A.",
""
]
]
|
quant-ph/0609118 | Radu Ionicioiu | Radu Ionicioiu | Entangling spins by measuring charge: a parity-gate toolbox | updated to the published version | Phys. Rev. A 75, 032339 (2007) | 10.1103/PhysRevA.75.032339 | null | quant-ph | null | The parity gate emerged recently as a promising resource for performing
universal quantum computation with fermions using only linear interactions.
Here we analyse the parity gate (P-gate) from a theoretical point of view in
the context of quantum networks. We present several schemes for entanglement
generation with P-gates and show that native networks simplify considerably the
resources required for producing multi-qubit entanglement, like n-GHZ states.
Other applications include a Bell-state analyser and teleportation. We also
show that cluster state fusion can be performed deterministically with parity
measurements. We then extend this analysis to hybrid quantum networks
containing spin and mode qubits. Starting from an easy-to-prepare resource
(spin-mode entanglement of single electrons) we show how to produce a spin
n-GHZ state with linear elements (beam-splitters and local spin-flips) and
charge-parity detectors; this state can be used as a resource in a spin quantum
computer or as a precursor for constructing cluster states. Finally, we
construct a novel spin CZ-gate by using the mode degrees of freedom as
ancillae.
| [
{
"version": "v1",
"created": "Fri, 15 Sep 2006 18:12:39 GMT"
},
{
"version": "v2",
"created": "Wed, 28 Mar 2007 14:42:04 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Ionicioiu",
"Radu",
""
]
]
|
quant-ph/0609119 | Dimitri Dounas-Frazer | D. R. Dounas-Frazer, A. M. Hermundstad and L. D. Carr | Ultracold Bosons in a Tilted Multi-level Double-Well Potential | 4 pages, 3 figures | Phys. Rev. Lett. 99, 200402 (2007) | 10.1103/PhysRevLett.99.200402 | null | quant-ph cond-mat.other | null | The N -body problem in a double well requires new features for quantum
information processing, macroscopic quantum superposition, and other
fundamental studies of quantum many body physics in ultracold atoms. One needs
(a) tilt, and (b) to go beyond the single-particle ground state in each well,
i.e., to two or more energy levels. For (a), we show that a small potential
difference between the wells, or tilt, causes the decoherence of Schrodinger
cat states. However, these states reappear when the tilt can be compensated by
atom-atom interactions; these tilted cat states constitute partial cats that
are protected from decoherence by the many body wavefunction. For (b), we
provide explicit criteria for when two energy levels are needed to describe the
state space. For typical experimental parameters, two levels are indeed
required for creation of cat states.
| [
{
"version": "v1",
"created": "Fri, 15 Sep 2006 22:19:50 GMT"
},
{
"version": "v2",
"created": "Tue, 22 May 2007 22:05:01 GMT"
},
{
"version": "v3",
"created": "Thu, 23 Aug 2007 00:09:12 GMT"
}
]
| 2010-12-16T00:00:00 | [
[
"Dounas-Frazer",
"D. R.",
""
],
[
"Hermundstad",
"A. M.",
""
],
[
"Carr",
"L. D.",
""
]
]
|
quant-ph/0609120 | Gregory P. Lafyatis | Andrei Modoran and Gregory Lafyatis | Spontaneous emission into a planar optical waveguide mode by an atom
outside the waveguide | 13 pages 3 figures | null | null | null | quant-ph | null | An electronically excited atom or molecule located outside but near a planar
optical waveguide can decay by spontaneous emission of a photon into a guided
mode of the waveguide. We outline a QED theory for calculating the probability
for this process and describe general physical insights from that theory. A
couple of representative examples are discussed in detail.
| [
{
"version": "v1",
"created": "Mon, 18 Sep 2006 18:35:30 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Modoran",
"Andrei",
""
],
[
"Lafyatis",
"Gregory",
""
]
]
|
quant-ph/0609121 | Aikaterini Mandilara | A. Mandilara, V. M. Akulin | Cooperative behavior of qutrits with dipole-dipole interactions | 5 pages, 3 figures. Minor corrections | null | 10.1088/0953-4075/40/9/S05 | null | quant-ph | null | We have identified a class of many body problems with analytic solution
beyond the mean-field approximation. This is the case where each body can be
considered as an element of an assembly of interacting particles that are
translationally frozen multi-level quantum systems and that do not change
significantly their initial quantum states during the evolution. In contrast,
the entangled collective state of the assembly experiences an appreciable
change. We apply this approach to interacting three-level systems.
| [
{
"version": "v1",
"created": "Sat, 16 Sep 2006 20:24:04 GMT"
},
{
"version": "v2",
"created": "Tue, 13 Mar 2007 14:16:08 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Mandilara",
"A.",
""
],
[
"Akulin",
"V. M.",
""
]
]
|
quant-ph/0609122 | Robert Alicki | Robert Alicki | False qubits II. Entanglement of Josephson junctions | 2 pages | null | null | null | quant-ph | null | The recent experimental evidence for entangled states of two Josephson
junction qubits is briefly discussed. It is argued that the interpretation of
the experimental data strongly depends on the assumed theoretical model.
Namely, the qubit states are supposed to be the lowest lying eigenstates of a
certain effective Hamiltonian and hence automatically orthogonal, while the
simple analysis within a more fundamental many-particle model shows that those
states should strongly overlap. This makes the standard interpretation of the
measurement procedure questionable.
| [
{
"version": "v1",
"created": "Sat, 16 Sep 2006 21:25:44 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Alicki",
"Robert",
""
]
]
|
quant-ph/0609123 | J. Q. You | J. Q. You, Xiang-bin Wang, Tetsufumi Tanamoto, Franco Nori | Efficient one-step generation of large cluster states with solid-state
circuits | 4 pages, 1 figure | Phys. Rev. A 75, 052319 (2007) | 10.1103/PhysRevA.75.052319 | null | quant-ph cond-mat.mes-hall cond-mat.supr-con | null | Highly entangled states called cluster states are a universal resource for
measurement-based quantum computing (QC). Here we propose an efficient method
for producing large cluster states using superconducting quantum circuits. We
show that a large cluster state can be efficiently generated in just one step
by turning on the inter-qubit coupling for a short time. Because the
inter-qubit coupling is only switched on during the time interval for
generating the cluster state, our approach is also convenient for preparing the
initial state for each qubit and for implementing one-way QC via single-qubit
measurements. Moreover, the cluster state is robust against parameter
variations.
| [
{
"version": "v1",
"created": "Sun, 17 Sep 2006 09:32:57 GMT"
},
{
"version": "v2",
"created": "Sat, 23 Dec 2006 14:12:09 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"You",
"J. Q.",
""
],
[
"Wang",
"Xiang-bin",
""
],
[
"Tanamoto",
"Tetsufumi",
""
],
[
"Nori",
"Franco",
""
]
]
|
quant-ph/0609124 | Andrei Khrennikov | Andrei Khrennikov | Quantum mechanics for military officers | Plenary talk at International Conference "Foundations of Probability
and Physics-4", Vaxjo, June-2006, and at the Congress of "Quantum Structures
Association", Malta, July-2006 | null | 10.1063/1.2713453 | null | quant-ph | null | We present a trivial probabilistic illustration for representation of quantum
mechanics as an algorithm for approximative calculation of averages.
| [
{
"version": "v1",
"created": "Sun, 17 Sep 2006 09:21:30 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Khrennikov",
"Andrei",
""
]
]
|
quant-ph/0609125 | Verstraete Frank | Y.-K. Liu, M. Christandl, and F. Verstraete | N-representability is QMA-complete | null | Phys. Rev. Lett. 98, 110503 (2007) | 10.1103/PhysRevLett.98.110503 | null | quant-ph | null | We study the computational complexity of the N-representability problem in
quantum chemistry. We show that this problem is QMA-complete, which is the
quantum generalization of NP-complete. Our proof uses a simple mapping from
spin systems to fermionic systems, as well as a convex optimization technique
that reduces the problem of finding ground states to N-representability.
| [
{
"version": "v1",
"created": "Sun, 17 Sep 2006 17:06:42 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Liu",
"Y. -K.",
""
],
[
"Christandl",
"M.",
""
],
[
"Verstraete",
"F.",
""
]
]
|
quant-ph/0609126 | Paul O'Hara | Paul O'Hara | SU(2) Relativity and the EPR Paradox | 8 pages, 1 figure | null | null | null | quant-ph | null | In the normal presentation of the EPR problem a comparison is made between
the (weak) Copenhagen interpretation of quantum mechanics which seems to
suggest that at times action at a distance may take place, and the hidden
parameter interpretation which must satisfy Bell's inequality, in contradiction
to the predictions of quantum mechanics. In this paper, we consider a
relativistic approach to the paradox. However, the frame of reference under
consideration is not the usual Lorenz frame but rather the spin frame of
reference which is invariant with respect to the SU(2) group.
| [
{
"version": "v1",
"created": "Sun, 17 Sep 2006 18:23:34 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"O'Hara",
"Paul",
""
]
]
|
quant-ph/0609127 | Young S Kim | Y. S. Kim and Marilyn E. Noz | Can you do quantum mechanics without Einstein? | Latex 11 pages, 7 figures; invited paper presented at the
International Conference on Foundations of Probability and Physics (Vaxjo,
Sweden, June 2006); to be published in the proceedings (AIP Conference
Proceedings Series); Minor corrections | AIPConf.Proc.889:152-161,2007 | 10.1063/1.2713454 | null | quant-ph hep-ph hep-th | null | The present form of quantum mechanics is based on the Copenhagen school of
interpretation. Einstein did not belong to the Copenhagen school, because he
did not believe in probabilistic interpretation of fundamental physical laws.
This is the reason why we are still debating whether there is a more
deterministic theory. One cause of this separation between Einstein and the
Copenhagen school could have been that the Copenhagen physicists thoroughly
ignored Einstein's main concern: the principle of relativity. Paul A. M. Dirac
was the first one to realize this problem. Indeed, from 1927 to 1963, Paul A.
M. Dirac published at least four papers to study the problem of making the
uncertainty relation consistent with Einstein's Lorentz covariance. It is
interesting to combine those papers by Dirac to make the uncertainty relation
consistent with relativity. It is shown that the mathematics of two coupled
oscillators enables us to carry out this job. We are then led to the question
of whether the concept of localized probability distribution is consistent with
Lorentz covariance.
| [
{
"version": "v1",
"created": "Sun, 17 Sep 2006 21:54:08 GMT"
},
{
"version": "v2",
"created": "Sat, 23 Sep 2006 18:03:57 GMT"
}
]
| 2009-09-29T00:00:00 | [
[
"Kim",
"Y. S.",
""
],
[
"Noz",
"Marilyn E.",
""
]
]
|
quant-ph/0609128 | Arvid Bessen | Arvid J. Bessen | Distributions of continuous-time quantum walks | 6 pages, 4 figures; added references | null | null | null | quant-ph | null | We study the distributions of the continuous-time quantum walk on a
one-dimensional lattice. In particular we will consider walks on unbounded
lattices, walks with one and two boundaries and Dirichlet boundary conditions,
and walks with periodic boundary conditions. We will prove that all
continuous-time quantum walks can be written as a series of Bessel functions of
the first kind and show how to approximate these series.
| [
{
"version": "v1",
"created": "Mon, 18 Sep 2006 00:33:53 GMT"
},
{
"version": "v2",
"created": "Mon, 16 Oct 2006 00:44:49 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Bessen",
"Arvid J.",
""
]
]
|
quant-ph/0609129 | Qiang Zhang | Qiang Zhang, Alexander Goebel, Claudia Wagenknecht, Yu-Ao Chen, Bo
Zhao, Tao Yang, Alois Mair, Joerg Schmiedmayer and Jian-Wei Pan | Experimental Quantum Teleportation of a Two-Qubit Composite System | 16pages, 4 figures | Nature Physics 2, 678 - 682 (2006) | 10.1038/nphys417 | null | quant-ph | null | Quantum teleportation, a way to transfer the state of a quantum system from
one location to another, is central to quantum communication and plays an
important role in a number of quantum computation protocols. Previous
experimental demonstrations have been implemented with photonic or ionic
qubits. Very recently long-distance teleportation and open-destination
teleportation have also been realized. Until now, previous experiments have
only been able to teleport single qubits. However, since teleportation of
single qubits is insufficient for a large-scale realization of quantum
communication and computation2-5, teleportation of a composite system
containing two or more qubits has been seen as a long-standing goal in quantum
information science. Here, we present the experimental realization of quantum
teleportation of a two-qubit composite system. In the experiment, we develop
and exploit a six-photon interferometer to teleport an arbitrary polarization
state of two photons. The observed teleportation fidelities for different
initial states are all well beyond the state estimation limit of 0.40 for a
two-qubit system. Not only does our six-photon interferometer provide an
important step towards teleportation of a complex system, it will also enable
future experimental investigations on a number of fundamental quantum
communication and computation protocols such as multi-stage realization of
quantum-relay, fault-tolerant quantum computation, universal quantum
error-correction and one-way quantum computation.
| [
{
"version": "v1",
"created": "Mon, 18 Sep 2006 10:17:35 GMT"
}
]
| 2007-06-13T00:00:00 | [
[
"Zhang",
"Qiang",
""
],
[
"Goebel",
"Alexander",
""
],
[
"Wagenknecht",
"Claudia",
""
],
[
"Chen",
"Yu-Ao",
""
],
[
"Zhao",
"Bo",
""
],
[
"Yang",
"Tao",
""
],
[
"Mair",
"Alois",
""
],
[
"Schmiedmayer",
"Joerg",
""
],
[
"Pan",
"Jian-Wei",
""
]
]
|
quant-ph/0609130 | Lu Chao-Yang | Chao-Yang Lu, Xiao-Qi Zhou, Otfried G\"uhne, Wei-Bo Gao, Jin Zhang,
Zhen-Sheng Yuan, Alexander Goebel, Tao Yang, and Jian-Wei Pan | Experimental entanglement of six photons in graph states | null | Nature Physics 3, 91-95 (2007). | 10.1038/nphys507 | null | quant-ph | null | Graph states are special kinds of multipartite entangled states that
correspond to mathematical graphs where the vertices take the role of quantum
spin systems and the edges represent interactions. They not only provide an
efficient model to study multiparticle entanglement, but also find wide
applications in quantum error correction, multi-party quantum communication and
most prominently, serve as the central resource in one-way quantum computation.
Here we report the creation of two special instances of graph states, the
six-photon Greenberger-Horne-Zeilinger states -- the largest photonic
Schr\"{o}dinger cat, and the six-photon cluster states-- a state-of-the-art
one-way quantum computer. Flexibly, slight modifications of our method allow
creation of many other graph states. Thus we have demonstrated the ability of
entangling six photons and engineering multiqubit graph states, and created a
test-bed for investigations of one-way quantum computation and studies of
multiparticle entanglement as well as foundational issues such as nonlocality
and decoherence.
| [
{
"version": "v1",
"created": "Mon, 18 Sep 2006 09:30:10 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Lu",
"Chao-Yang",
""
],
[
"Zhou",
"Xiao-Qi",
""
],
[
"Gühne",
"Otfried",
""
],
[
"Gao",
"Wei-Bo",
""
],
[
"Zhang",
"Jin",
""
],
[
"Yuan",
"Zhen-Sheng",
""
],
[
"Goebel",
"Alexander",
""
],
[
"Yang",
"Tao",
""
],
[
"Pan",
"Jian-Wei",
""
]
]
|
quant-ph/0609131 | Sahel Ashhab | S. Ashhab, Koji Maruyama, Franco Nori | Observing quantum non-locality in the entanglement between modes of
massive particles | 8 pages (two-column), 2 figures | Phys. Rev. A 75, 022108 (2007) | 10.1103/PhysRevA.75.022108 | null | quant-ph cond-mat.other | null | We consider the question of whether it is possible to use the entanglement
between spatially separated modes of massive particles to observe nonlocal
quantum correlations. Mode entanglement can be obtained using a single
particle, indicating that it requires careful consideration before concluding
whether experimental observation, e.g. violation of Bell inequalities, is
possible or not. In the simplest setups analogous to optics experiments, that
observation is prohibited by fundamental conservation laws. However, we show
that using auxiliary particles, mode entanglement can be converted into forms
that allow the observation of quantum non-locality. The probability of
successful conversion depends on the nature and number of auxiliary particles
used. In particular, we find that an auxiliary Bose-Einstein condensate allows
the conversion arbitrarily many times with a small error that depends only on
the initial state of the condensate.
| [
{
"version": "v1",
"created": "Mon, 18 Sep 2006 11:06:03 GMT"
},
{
"version": "v2",
"created": "Wed, 28 Feb 2007 17:11:41 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Ashhab",
"S.",
""
],
[
"Maruyama",
"Koji",
""
],
[
"Nori",
"Franco",
""
]
]
|
quant-ph/0609132 | Bruno Zerbo | G. Fonte, B. Zerbo | Classical billiards and double-slit quantum interference | 12 pages, 10 figures, 2 tables | null | null | null | quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We carry out a numerical simulation about the occurrence of interference
fringes in experiments where an initial Gaussian wave packet evolves inside a
billiard domain with two slits on the boundary. Our simulation extends a
previous work by Casati and Prosen and it is aimed to test their surprising
conclusion that the fringes disappear in the experiments with fully chaotic
billiards. According to the results found, we are led to reassess this
remarkable effect of classical dynamics on quantum interference. Actually, we
highlight another factor which acts on interference: a symmetry condition (SC)
concerning the experimental set-up. This condition seems even to play a role
more important than classical chaos. Indeed, when the SC is verified, classical
chaos has no effect, whereas when the SC is violated classical chaos turns out
to be an additional factor that causes dephasing at the slits. We explain the
respective roles of these two factors, by specifying the physical mechanism
through which they influence the interference patterns. This mechanism depends
both on the position and direction of the initial wave packet and on certain
its recurrences which occur especially in the regular billiards.
| [
{
"version": "v1",
"created": "Mon, 18 Sep 2006 11:51:37 GMT"
},
{
"version": "v2",
"created": "Wed, 20 Sep 2006 10:25:35 GMT"
},
{
"version": "v3",
"created": "Thu, 21 Sep 2006 07:42:22 GMT"
},
{
"version": "v4",
"created": "Tue, 1 Nov 2011 00:47:47 GMT"
}
]
| 2011-11-02T00:00:00 | [
[
"Fonte",
"G.",
""
],
[
"Zerbo",
"B.",
""
]
]
|
quant-ph/0609133 | Igor Lesanovsky | Igor Lesanovsky and Wolf von Klitzing | Spontaneous emergence of angular momentum Josephson oscillations in
coupled annular Bose-Einstein condensates | null | Phys. Rev. Lett. 98-5, 050401 (2007) | 10.1103/PhysRevLett.98.050401 | null | quant-ph cond-mat.quant-gas | null | We investigate the nonlinear dynamics of two coupled annular Bose-Einstein
condensates (BECs). For certain values of the coupling strength the nonrotating
ground state is unstable with respect to fluctuations in the higher angular
momentum modes. The two branched Bogoliubov spectrum exhibits distinct regions
of instability enabling one to selectively occupy certain angular momentum
modes. For sufficiently long evolution times angular momentum Josephson
oscillations spontaneously appear, breaking the initial chiral symmetry of the
BECs.
| [
{
"version": "v1",
"created": "Mon, 18 Sep 2006 14:29:50 GMT"
},
{
"version": "v2",
"created": "Mon, 27 Nov 2006 08:00:06 GMT"
}
]
| 2013-11-26T00:00:00 | [
[
"Lesanovsky",
"Igor",
""
],
[
"von Klitzing",
"Wolf",
""
]
]
|
quant-ph/0609134 | Matthew Jones | Matthew P. A. Jones (LCFIO), Jerome Beugnon (LCFIO), Alpha Ga\"etan
(LCFIO), Junxiang Zhang (LCFIO), Gaetan Messin (LCFIO), Antoine Browaeys
(LCFIO), Philippe Grangier (LCFIO) | Fast Quantum State Control of a Single Trapped Neutral Atom | null | Physical review A 75 (11/04/2007) 040301(R) | 10.1103/PhysRevA.75.040301 | null | quant-ph | null | We demonstrate the initialisation, read-out and high-speed manipulation of a
qubit stored in a single 87 Rb atom trapped in a submicron-size optical
tweezer. Single qubit rotations are performed on a sub-100 ns time scale using
two-photon Raman transitions. Using the ``spin-echo'' technique, we measure an
irreversible dephasing time of 34 ms. The read-out of the single atom qubit is
at the quantum projection noise limit when averaging up to 1000 individual
events.
| [
{
"version": "v1",
"created": "Mon, 18 Sep 2006 16:35:55 GMT"
},
{
"version": "v2",
"created": "Tue, 24 Apr 2007 19:20:24 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Jones",
"Matthew P. A.",
"",
"LCFIO"
],
[
"Beugnon",
"Jerome",
"",
"LCFIO"
],
[
"Gaëtan",
"Alpha",
"",
"LCFIO"
],
[
"Zhang",
"Junxiang",
"",
"LCFIO"
],
[
"Messin",
"Gaetan",
"",
"LCFIO"
],
[
"Browaeys",
"Antoine",
"",
"LCFIO"
],
[
"Grangier",
"Philippe",
"",
"LCFIO"
]
]
|
quant-ph/0609135 | J Roesch | Juergen Roesch, Xian-Min Jing, Juan Yin, Tao Yang, Jian-Wei Pan | Non-local generation of entanglement of photons which do not meet each
other | 16 pages, 1 table, 4 figures | null | null | null | quant-ph | null | We report for the first time in an ancilla-free process a non-local
entanglement between two single photons which do not meet. For our experiment
we derive a simple and efficient method to entangle two single photons using
post-selection technology. The photons are guided into an interferometer setup
without the need for ancilla photons for projection into the Bell-states. After
passing the output ports, the photons are analyzed using a bell state analyzer
on each side. The experimental data clearly shows a non-local interaction
between these photons, surpassing the limit set by the CHSH-inequality with an
S-value of 2.54 and 24 standard deviations.
| [
{
"version": "v1",
"created": "Mon, 18 Sep 2006 17:04:48 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Roesch",
"Juergen",
""
],
[
"Jing",
"Xian-Min",
""
],
[
"Yin",
"Juan",
""
],
[
"Yang",
"Tao",
""
],
[
"Pan",
"Jian-Wei",
""
]
]
|
quant-ph/0609136 | John Calsamiglia | J. Calsamiglia, Ll. Masanes, R. Munoz-Tapia, A. Acin, E. Bagan | Optimal discrimination of mixed states: the quantum Chernoff bound | Withdrawn due to flaw in proof of Theorem 1. Superseded by pre-print
quant-ph/0610027 | null | null | null | quant-ph | null | This paper has been withdrawn by the authors, due to a flaw in the proof of
Theorem 1. This preprint is superseded by quant-ph/0610027, where a correct
proof can be found. Thanks to Rainer Siegmund-Schultze for spotting the error.
| [
{
"version": "v1",
"created": "Mon, 18 Sep 2006 17:44:16 GMT"
},
{
"version": "v2",
"created": "Wed, 4 Oct 2006 19:54:21 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Calsamiglia",
"J.",
""
],
[
"Masanes",
"Ll.",
""
],
[
"Munoz-Tapia",
"R.",
""
],
[
"Acin",
"A.",
""
],
[
"Bagan",
"E.",
""
]
]
|
quant-ph/0609137 | ChengZhi Peng | Xiang-Bin Wang, Cheng-Zhi Peng, and Jian-Wei Pan | Simple protocol for secure decoy-state quantum key distribution with a
loosely controlled source | null | Appl. Phys. Lett., 90, 031110(2007) | 10.1063/1.2431718 | null | quant-ph | null | The method of decoy-state quantum key distribution (QKD) requests different
intensities of light pulses. Existing theory has assumed exact control of
intensities. Here we propose a simple protocol which is secure and efficient
even there are errors in intensity control. In our protocol, decoy pulses and
signal pulses are generated from the same father pulses with a two-value
attenuation. Given the upper bound of fluctuation of the father pulses, our
protocol is secure provided that the two-value attenuation is done exactly. We
propose to use unbalanced beam-splitters for a stable attenuation. Given that
the intensity error is bounded by $\pm5%$, with the same key rate, our method
can achieve a secure distance only 1 km shorter than that of an ideal protocol
with exactly controlled source.
| [
{
"version": "v1",
"created": "Mon, 18 Sep 2006 18:55:24 GMT"
},
{
"version": "v2",
"created": "Wed, 16 Jan 2008 07:43:03 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Wang",
"Xiang-Bin",
""
],
[
"Peng",
"Cheng-Zhi",
""
],
[
"Pan",
"Jian-Wei",
""
]
]
|
quant-ph/0609138 | Cristopher Moore | Cristopher Moore and Alexander Russell | On the Impossibility of a Quantum Sieve Algorithm for Graph Isomorphism | null | null | null | null | quant-ph cs.CC math.RT | null | It is known that any quantum algorithm for Graph Isomorphism that works
within the framework of the hidden subgroup problem (HSP) must perform highly
entangled measurements across Omega(n log n) coset states. One of the only
known models for how such a measurement could be carried out efficiently is
Kuperberg's algorithm for the HSP in the dihedral group, in which quantum
states are adaptively combined and measured according to the decomposition of
tensor products into irreducible representations. This ``quantum sieve'' starts
with coset states, and works its way down towards representations whose
probabilities differ depending on, for example, whether the hidden subgroup is
trivial or nontrivial.
In this paper we give strong evidence that no such approach can succeed for
Graph Isomorphism. Specifically, we consider the natural reduction of Graph
Isomorphism to the HSP over the the wreath product S_n \wr Z_2. We show, modulo
a group-theoretic conjecture regarding the asymptotic characters of the
symmetric group, that no matter what rule we use to adaptively combine quantum
states, there is a constant b > 0 such that no algorithm in this family can
solve Graph Isomorphism in e^{b sqrt{n}} time. In particular, such algorithms
are essentially no better than the best known classical algorithms, whose
running time is e^{O(sqrt{n \log n})}.
| [
{
"version": "v1",
"created": "Mon, 18 Sep 2006 20:01:41 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Moore",
"Cristopher",
""
],
[
"Russell",
"Alexander",
""
]
]
|
quant-ph/0609139 | Timothy C. Ralph | T. C. Ralph, G. J. Milburn, T. Downes | Gravitationally Induced Decoherence of Optical Entanglement | Error corrected and figure 2 replaced | null | null | null | quant-ph | null | We propose an experiment in which an entangled pair of optical pulses are
propagated through non-uniform gravitational fields. A field operator
calculation of this situation predicts decoherence of the optical entanglement
under experimentally realistic conditions.
| [
{
"version": "v1",
"created": "Mon, 18 Sep 2006 23:28:46 GMT"
},
{
"version": "v2",
"created": "Fri, 23 Mar 2007 03:54:59 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Ralph",
"T. C.",
""
],
[
"Milburn",
"G. J.",
""
],
[
"Downes",
"T.",
""
]
]
|
quant-ph/0609140 | Xiao-qiang Xi | Xiao-Qiang Xi, R. H. Yue, W. M. Liu | Pairwise Entanglement and Local Polarization of Heisenberg Model | 1 figures, 2 tables | null | null | null | quant-ph | null | The pairwise entanglement and local polarization of the ground state are
discussed by studying the Heisenberg XX model in finite qubit case. The results
show that: the ground state is composed by the micro state with the minimal
total spin 0 (for even qubit) or 1/2 (for odd qubit), local polarization (LP)
has intimate relation with the probability of the micro state in the ground
state, the stronger the LP the smaller the probability, the same LP
corresponding to the same probability; the pairwise entanglement of the ground
state is the biggest in all the eigenvectors. We find when the qubit is small,
the degenerate of state will decrease the pairwise entanglement, there has
great different between the odd and the even qubit chain; when the qubit number
is big, the effect of qubit number to the pairwise entanglement will disappear,
the limited value will be round about 0.3424.
| [
{
"version": "v1",
"created": "Tue, 19 Sep 2006 03:18:37 GMT"
},
{
"version": "v2",
"created": "Sat, 18 Nov 2006 07:25:27 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Xi",
"Xiao-Qiang",
""
],
[
"Yue",
"R. H.",
""
],
[
"Liu",
"W. M.",
""
]
]
|
quant-ph/0609141 | Raffaele Romano | Raffaele Romano | Resonant purification of mixed states for closed and open quantum
systems | 4 pages, LaTex | Phys. Rev. A 75, 024301 (2007) | 10.1103/PhysRevA.75.024301 | null | quant-ph | null | Pure states are fundamental for the implementation of quantum technologies,
and several methods for the purification of the state of a quantum system S
have been developed in the past years. In this letter we present a new
approach, based on the interaction of S with an auxiliary system P, having a
wide range of applicability. Considering two-level systems S and P and assuming
a particular interaction between them, we prove that complete purifications can
be obtained under suitable conditions on the parameters characterizing P. Using
analytical and numerical tools, we show that the purification process exhibits
a resonant behavior in both the cases of system isolated from the external
environment or not.
| [
{
"version": "v1",
"created": "Tue, 19 Sep 2006 06:13:12 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Romano",
"Raffaele",
""
]
]
|
quant-ph/0609142 | Lawrence P. Horwitz | Ari Belenkiy, Steve Shnider, Lawrence Horwitz | The Geometry of Stochastic Reduction of an Entangled System | 10 pages, Latex | null | null | null | quant-ph | null | We show that the method of stochastic reduction of linear superpositions can
be applied to the process of disentanglement for the spin-0 state of two
spin-1/2 particles. We describe the geometry of this process in the framework
of the complex projective space
| [
{
"version": "v1",
"created": "Tue, 19 Sep 2006 06:58:10 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Belenkiy",
"Ari",
""
],
[
"Shnider",
"Steve",
""
],
[
"Horwitz",
"Lawrence",
""
]
]
|
quant-ph/0609143 | Arzhang Ardavan | Arzhang Ardavan, Olivier Rival, John J.L. Morton, Stephen J. Blundell,
Alexei M. Tyryshkin, Grigore A. Timco and Richard E.P. Winnpenny | Will spin-relaxation times in molecular magnets permit quantum
information processing? | 4 pages, 3 figures, in press at Physical Review Letters | null | 10.1103/PhysRevLett.98.057201 | null | quant-ph | null | Using X-band pulsed electron spin resonance, we report the intrinsic
spin-lattice ($T_1$) and phase coherence ($T_2$) relaxation times in molecular
nanomagnets for the first time. In Cr$_7M$ heterometallic wheels, with $M$ = Ni
and Mn, phase coherence relaxation is dominated by the coupling of the electron
spin to protons within the molecule. In deuterated samples $T_2$ reaches 3
$\mu$s at low temperatures, which is several orders of magnitude longer than
the duration of spin manipulations, satisfying a prerequisite for the
deployment of molecular nanomagnets in quantum information applications.
| [
{
"version": "v1",
"created": "Tue, 19 Sep 2006 11:34:07 GMT"
},
{
"version": "v2",
"created": "Wed, 4 Oct 2006 14:07:56 GMT"
},
{
"version": "v3",
"created": "Fri, 15 Dec 2006 17:50:40 GMT"
},
{
"version": "v4",
"created": "Mon, 15 Jan 2007 18:47:39 GMT"
},
{
"version": "v5",
"created": "Tue, 16 Jan 2007 16:15:16 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Ardavan",
"Arzhang",
""
],
[
"Rival",
"Olivier",
""
],
[
"Morton",
"John J. L.",
""
],
[
"Blundell",
"Stephen J.",
""
],
[
"Tyryshkin",
"Alexei M.",
""
],
[
"Timco",
"Grigore A.",
""
],
[
"Winnpenny",
"Richard E. P.",
""
]
]
|
quant-ph/0609144 | Alexandre Dodonov V | A. V. Dodonov, S. S. Mizrahi, and V. V. Dodonov | Quantum master equations from classical Lagrangians with two stochastic
forces | 10 pages, no figures | Physical Review E 75, 011132 (2007) | 10.1103/PhysRevE.75.011132 | null | quant-ph | null | We show how a large family of master equations, describing quantum Brownian
motion of a harmonic oscillator with translationally invariant damping, can be
derived within a phenomenological approach, based on the assumption that an
environment can be simulated by two classical stochastic forces. This family is
determined by three time-dependent correlation functions (besides the frequency
and damping coefficients), and it includes as special cases the known master
equations, whose dissipative part is bilinear with respect to the operators of
coordinate and momentum.
| [
{
"version": "v1",
"created": "Tue, 19 Sep 2006 11:48:09 GMT"
},
{
"version": "v2",
"created": "Tue, 7 Nov 2006 23:43:04 GMT"
},
{
"version": "v3",
"created": "Fri, 2 Feb 2007 03:20:14 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Dodonov",
"A. V.",
""
],
[
"Mizrahi",
"S. S.",
""
],
[
"Dodonov",
"V. V.",
""
]
]
|
quant-ph/0609145 | Galina L. Klimchitskaya | G. L. Klimchitskaya and V. M. Mostepanenko | Experiment and theory in the Casimir effect | 11 pages, 14 figures | Contemp.Phys. 47 (2006) 131-144 | 10.1080/00107510600693683 | null | quant-ph cond-mat.other hep-th | null | Casimir effect is the attractive force which acts between two plane parallel,
closely spaced, uncharged, metallic plates in vacuum. This phenomenon was
predicted theoretically in 1948 and reliably investigated experimentally only
in recent years. In fact, the Casimir force is similar to the familiar van der
Waals force in the case of relatively large separations when the relativistic
effects come into play. We review the most important experiments on measuring
the Casimir force by means of torsion pendulum, atomic force microscope and
micromechanical torsional oscillator. Special attention is paid to the puzzle
of the thermal Casimir force, i.e., to the apparent violation of the third law
of thermodynamics when the Lifshitz theory of dispersion forces is applied to
real metals. Thereafter we discuss the role of the Casimir force in nanosystems
including the stiction phenomenon, actuators, and interaction of hydrogen atoms
with carbon nanotubes. The applications of the Casimir effect for constraining
predictions of extra-dimensional unification schemes and other physics beyond
the standard model are also considered.
| [
{
"version": "v1",
"created": "Tue, 19 Sep 2006 11:53:29 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Klimchitskaya",
"G. L.",
""
],
[
"Mostepanenko",
"V. M.",
""
]
]
|
quant-ph/0609146 | Honglin Liu | Honglin Liu, Jing Cheng, Yanfeng Bai and Shensheng Han | Fourier Analysis of Ghost Imaging | 5 pages,4 figures | null | null | null | quant-ph | null | Fourier analysis of ghost imaging (FAGI) is proposed in this paper to analyze
the properties of ghost imaging with thermal light sources. This new theory is
compatible with the general correlation theory of intensity fluctuation and
could explain some amazed phenomena. Furthermore we design a series of
experiments to verify the new theory and investigate the inherent properties of
ghost imaging.
| [
{
"version": "v1",
"created": "Tue, 19 Sep 2006 14:27:31 GMT"
},
{
"version": "v2",
"created": "Wed, 20 Sep 2006 07:07:08 GMT"
},
{
"version": "v3",
"created": "Thu, 28 Sep 2006 14:20:16 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Liu",
"Honglin",
""
],
[
"Cheng",
"Jing",
""
],
[
"Bai",
"Yanfeng",
""
],
[
"Han",
"Shensheng",
""
]
]
|
quant-ph/0609147 | Pedro Sancho | Pedro Sancho | Compositeness effects, Pauli's principle and entanglement | null | J. Phys. A 39 (2006) 12525-12537 | 10.1088/0305-4470/39/40/017 | null | quant-ph | null | We analyse some compositeness effects and their relation with entanglement.
We show that the purity of a composite system increases, in the sense of the
expectation values of the deviation operators, with large values of the
entanglement between the components of the system. We also study the validity
of Pauli's principle in composite systems. It is valid within the limits of
application of the approach presented here. We also present an example of two
identical fermions, one of them entangled with a distinguishable particle,
where the exclusion principle cannot be applied. This result can be important
in the description of open systems.
| [
{
"version": "v1",
"created": "Tue, 19 Sep 2006 17:12:23 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Sancho",
"Pedro",
""
]
]
|
quant-ph/0609148 | Irina Dobrovolska | I.V. Dobrovolska, R. S. Tutik | A new perturbation technique for eigenenergies of the screened coulomb
potential | null | Proc. 10th Int. Conf. on Mathematical Methods in Electromagnetic
Theory, Dniepropetrovsk, Ukraine, Sept. 14-17, 2004, pp. 341-343 | null | null | quant-ph | null | The explicit semiclassical treatment of the logarithmic perturbation theory
for the bound-state problem of the radial Shrodinger equation with the screened
Coulomb potential is developed. Based upon h-expansions and new quantization
conditions a novel procedure for deriving perturbation expansions is offered.
Avoiding disadvantages of the standard approach, new handy recursion formulae
with the same simple form both for ground and excited states have been
obtained.
| [
{
"version": "v1",
"created": "Tue, 19 Sep 2006 16:00:34 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Dobrovolska",
"I. V.",
""
],
[
"Tutik",
"R. S.",
""
]
]
|
quant-ph/0609149 | Jens Eisert | D. Gross, J. Eisert | Novel schemes for measurement-based quantum computation | 5 pages RevTeX, 1 figure, many diagrams. Title changed, presentation
improved, material added | Phys. Rev. Lett. 98, 220503 (2007) | 10.1103/PhysRevLett.98.220503 | null | quant-ph cond-mat.other | null | We establish a framework which allows one to construct novel schemes for
measurement-based quantum computation. The technique further develops tools
from many-body physics - based on finitely correlated or projected entangled
pair states - to go beyond the cluster-state based one-way computer. We
identify resource states that are radically different from the cluster state,
in that they exhibit non-vanishing correlation functions, can partly be
prepared using gates with non-maximal entangling power, or have very different
local entanglement properties. In the computational models, the randomness is
compensated in a different manner. It is shown that there exist resource states
which are locally arbitrarily close to a pure state. Finally, we comment on the
possibility of tailoring computational models to specific physical systems as,
e.g. cold atoms in optical lattices.
| [
{
"version": "v1",
"created": "Wed, 20 Sep 2006 18:11:47 GMT"
},
{
"version": "v2",
"created": "Wed, 11 Oct 2006 13:36:20 GMT"
},
{
"version": "v3",
"created": "Tue, 6 Mar 2007 21:26:21 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Gross",
"D.",
""
],
[
"Eisert",
"J.",
""
]
]
|
quant-ph/0609150 | Alejandro Saenz | Sergey Grishkevich and Alejandro Saenz | Influence of a tight isotropic harmonic trap on photoassociation in
ultracold homonuclear alkali gases | 19 pages, 17 figures | null | 10.1103/PhysRevA.76.022704 | null | quant-ph | null | The influence of a tight isotropic harmonic trap on photoassociation of two
ultracold alkali atoms forming a homonuclear diatomic is investigated using
realistic atomic interaction potentials. Confinement of the initial atom pair
due to the trap leads to a uniform strong enhancement of the photoassociation
rate to most, but also to a strongly suppressed rate for some final states.
Thus tighter traps do not necessarily enhance the photoassociation rate. A
further massive enhancement of the rate is found for strong interatomic
interaction potentials. The details of this interaction play a minor role,
except for large repulsive interactions for which a sharp window occurs in the
photoassociation spectrum as is known from the trap-free case. A comparison
with simplified models describing the atomic interaction like the
pseudopotential approximation shows that they often provide reasonable
estimates for the trap-induced enhancement of the photoassociation rate even if
the predicted rates can be completely erroneous.
| [
{
"version": "v1",
"created": "Tue, 19 Sep 2006 20:17:30 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Grishkevich",
"Sergey",
""
],
[
"Saenz",
"Alejandro",
""
]
]
|
quant-ph/0609151 | Zeng-Bing Chen | Zeng-Bing Chen, Bo Zhao, Yu-Ao Chen, Joerg Schmiedmayer, Jian-Wei Pan | Fault-tolerant quantum repeater with atomic ensembles and linear optics | Comments are welcome, to appear in Phys. Rev. A, accepted version | Phys. Rev. A 76, 022329 (2007) | 10.1103/PhysRevA.76.022329 | null | quant-ph | null | We present a detailed analysis of a new robust quantum repeater architecture
building on the original DLCZ protocol [L.M. Duan \textit{et al.}, Nature
(London) \textbf{414}, 413 (2001)]. The new architecture is based on two-photon
Hong-Ou-Mandel-type interference which relaxes the long-distance
interferometric stability requirements by about 7 orders of magnitude, from
sub-wavelength for the single photon interference required by DLCZ to the
coherence length of the photons, thereby removing the weakest point in the DLCZ
schema. Our proposal provides an exciting possibility for robust and realistic
long-distance quantum communication.
| [
{
"version": "v1",
"created": "Wed, 20 Sep 2006 08:13:25 GMT"
},
{
"version": "v2",
"created": "Fri, 8 Jun 2007 08:26:00 GMT"
},
{
"version": "v3",
"created": "Thu, 12 Jul 2007 08:24:38 GMT"
}
]
| 2011-11-09T00:00:00 | [
[
"Chen",
"Zeng-Bing",
""
],
[
"Zhao",
"Bo",
""
],
[
"Chen",
"Yu-Ao",
""
],
[
"Schmiedmayer",
"Joerg",
""
],
[
"Pan",
"Jian-Wei",
""
]
]
|
quant-ph/0609152 | Hideo Kosaka | H. Kosaka, Y. Rikitake, H. Imamura, Y. Mitsumori and K. Edamatsu | Negative Polarization through Photon to Electron Spin Polarization
Transfer in GaAs Quantum Wells | 4 pages, 3 figures. Submitted to Phys. Rev. B | null | null | null | quant-ph | null | We demonstrate negative polarization created by light-hole exciton excitation
in g-factor engineered GaAs quantum wells measured by time-resolved Kerr
rotation and polarization-resolved photoluminescence. This negative
polarization is a result of polarization transfer from a photon to an electron
spin mediated by a light hole. This demonstration is an important step towards
achieving quantum media conversion from a photonic qubit to an electron spin
qubit required for building a quantum repeater.
| [
{
"version": "v1",
"created": "Wed, 20 Sep 2006 09:56:55 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Kosaka",
"H.",
""
],
[
"Rikitake",
"Y.",
""
],
[
"Imamura",
"H.",
""
],
[
"Mitsumori",
"Y.",
""
],
[
"Edamatsu",
"K.",
""
]
]
|
quant-ph/0609153 | Masahide Sasaki | K. Wakui, H. Takahashi, A. Furusawa, M. Sasaki | Controllable generation of highly nonclassical states from nearly pure
squeezed vacua | 6 pages, 4 figures | Optics Express, Vol. 15 Issue 6, pp. 3568-3574 (2007). | 10.1364/OE.15.003568 | null | quant-ph | null | We present controllable generation of various kinds of highly nonclassical
states of light, including the single photon state and superposition states of
mesoscopically distinct components. The high nonclassicality of the generated
states is measured by the negativity of the Wigner function, which is largest
ever observed to our knowledge. Our scheme is based on photon subtraction from
a nearly pure squeezed vacuum, generated from an optical parametric oscillator
with a periodically-poled KTiOPO$_4$ crystal as a nonlinear medium. This is an
important step to realize basic elements of universal quantum gates, and to
serve as a highly nonclassical input probe for spectroscopy and the study of
quantum memory.
| [
{
"version": "v1",
"created": "Wed, 20 Sep 2006 11:04:51 GMT"
}
]
| 2010-02-05T00:00:00 | [
[
"Wakui",
"K.",
""
],
[
"Takahashi",
"H.",
""
],
[
"Furusawa",
"A.",
""
],
[
"Sasaki",
"M.",
""
]
]
|
quant-ph/0609154 | Zeng-Bing Chen | Bo Zhao, Zeng-Bing Chen, Yu-Ao Chen, Joerg Schmiedmayer, Jian-Wei Pan | Robust creation of entanglement between remote memory qubits | Comments are welcome, to appear in Phys. Rev. Lett., accepted version | Phys. Rev. Lett. 98, 240502 (2007) | 10.1103/PhysRevLett.98.240502 | null | quant-ph | null | In this Letter we propose a robust quantum repeater architecture building on
the original DLCZ protocol [L.M. Duan \textit{et al.}, Nature \textbf{414}, 413
(2001)]. The architecture is based on two-photon Hong-Ou-Mandel-type
interference which relaxes the long distance stability requirements by about 7
orders of magnitude, from sub wavelength for the single photon interference
required by DLCZ to the coherence length of the photons. Our proposal provides
an exciting possibility for robust and realistic long distance quantum
communication.
| [
{
"version": "v1",
"created": "Wed, 20 Sep 2006 12:35:29 GMT"
},
{
"version": "v2",
"created": "Fri, 8 Jun 2007 08:42:38 GMT"
}
]
| 2011-11-09T00:00:00 | [
[
"Zhao",
"Bo",
""
],
[
"Chen",
"Zeng-Bing",
""
],
[
"Chen",
"Yu-Ao",
""
],
[
"Schmiedmayer",
"Joerg",
""
],
[
"Pan",
"Jian-Wei",
""
]
]
|
quant-ph/0609155 | Arnaud Rouzee | Arnaud Rouzee, Vincent Renard, Stephane Guerin, Olivier Faucher, and
Bruno Lavorel | Optical gratings induced by field-free alignment of molecules | 10 pages, 5 figures, submitted to PRA | null | 10.1103/PhysRevA.75.013419 | null | quant-ph | null | We analyze the alignment of molecules generated by a pair of crossed
ultra-short pump pulses of different polarizations by a technique based on the
induced time-dependent gratings. Parallel polarizations yield an intensity
grating, while perpendicular polarizations induce a polarization grating. We
show that both configurations can be interpreted at moderate intensity as an
alignment induced by a single polarized pump pulse. The advantage of the
perpendicular polarizations is to give a signal of alignment that is free from
the plasma contribution. Experiments on femtosecond transient gratings with
aligned molecules were performed in CO2 at room temperature in a static cell
and at 30 K in a molecular expansion jet.
| [
{
"version": "v1",
"created": "Wed, 20 Sep 2006 15:14:45 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Rouzee",
"Arnaud",
""
],
[
"Renard",
"Vincent",
""
],
[
"Guerin",
"Stephane",
""
],
[
"Faucher",
"Olivier",
""
],
[
"Lavorel",
"Bruno",
""
]
]
|
quant-ph/0609156 | John Carroll | John E. Carroll | A photon-like wavepacket with quantised properties based on classical
Maxwell's equations | 20 pages, 7 figures | null | null | null | quant-ph | null | A photon-like wavepacket based on novel solutions of Maxwell's equations is
proposed. It is believed to be the first 'classical' model that contains so
many of the accepted quantum features. In this new work, novel solutions to
Maxwell's classical equations in dispersive guides are considered where local
helical twists with an arbitrary angular frequency W modulate a classical mode
(angular frequency w, group velocity vg). The modal field patterns are
unchanged, apart from the twist, provided that the helical velocity vh equals
vg. Pairs of resonating retarded and advanced waves with modal and helical
frequencies (w,W) and (w,-W)respectively, trap one temporal period of the
underlying classical mode forming a photon-like packet provided W = (M+1/2)w:
'Schrodinger' frequencies. This theory supports experimental evidence that the
photon velocity does not change with M in dispersive systems. Promotion and
demotion increase or decrease the helical frequencies in units of w. An energy
of interaction between retarded and advanced waves in the wave-packet is also
proportional to these helical frequencies W = (M+1/2)w similar to Planck's law.
Group velocity and polarisation are unaffected by the value of M. Advanced
waves enable phase and polarisation to be predicted along all future paths and
may help to explain the outcomes of experiments on delayed-choice interference
and entanglement, without causality being violated.
| [
{
"version": "v1",
"created": "Wed, 20 Sep 2006 15:18:39 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Carroll",
"John E.",
""
]
]
|
quant-ph/0609157 | B. Roy Frieden | B. Roy Frieden, Bernard H. Soffer | Information-theoretic significance of the Wigner distribution | pdf version has 16 pages. No figures. Accepted for publ. in PRA | null | 10.1103/PhysRevA.74.052108 | null | quant-ph | null | A coarse grained Wigner distribution p_{W}(x,u) obeying positivity derives
out of information-theoretic considerations. Let p(x,u) be the unknown joint
PDF (probability density function) on position- and momentum fluctuations x,u
for a pure state particle. Suppose that the phase part Psi(x,z) of its Fourier
transform F.T.[p(x,u)]=|Z(x,z)|exp[iPsi(x,z)] is constructed as a hologram.
(Such a hologram is often used in heterodyne interferometry.) Consider a
particle randomly illuminating this phase hologram. Let its two position
coordinates be measured. Require that the measurements contain an extreme
amount of Fisher information about true position, through variation of the
phase function Psi(x,z). The extremum solution gives an output PDF p(x,u) that
is the convolution of the Wigner p_{W}(x,u) with an instrument function
defining uncertainty in either position x or momentum u. The convolution arises
naturally out of the approach, and is one-dimensional, in comparison with the
two-dimensional convolutions usually proposed for coarse graining purposes. The
output obeys positivity, as required of a PDF, if the one-dimensional
instrument function is sufficiently wide. The result holds for a large class of
systems: those whose amplitudes a(x) are the same at their boundaries
(Examples: states a(x) with positive parity; with periodic boundary conditions;
free particle trapped in a box).
| [
{
"version": "v1",
"created": "Wed, 20 Sep 2006 19:35:04 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Frieden",
"B. Roy",
""
],
[
"Soffer",
"Bernard H.",
""
]
]
|
quant-ph/0609158 | Per Kristian Rekdal | Per K. Rekdal, Bo-Sture K. Skagerstam | Decay Processes in the Presence of Thin Superconducting Films | 5 pages, 2 figures | null | 10.1103/PhysRevA.75.022904 | null | quant-ph | null | In a recent paper [Phys. Rev. Lett. 97, 070401 (2006)] the transition rate of
magnetic spin-flip of a neutral two-level atom trapped in the vicinity of a
thick superconducting body was studied. In the present paper we will extend
these considerations to a situation with an atom at various distances from a
dielectric film. Rates for the corresponding electric dipole-flip transition
will also be considered. The rates for these atomic flip transitions can be
reduced or enhanced, and in some situations they can even be completely
suppressed. For a superconducting film or a thin film of a perfect conducting
material various analytical expressions are derived that reveals the dependence
of the physical parameters at hand.
| [
{
"version": "v1",
"created": "Wed, 20 Sep 2006 20:09:54 GMT"
}
]
| 2013-05-29T00:00:00 | [
[
"Rekdal",
"Per K.",
""
],
[
"Skagerstam",
"Bo-Sture K.",
""
]
]
|
quant-ph/0609159 | R. F. O'Connell | R. F. O'Connell | Does the Third Law of Thermodynamics hold in the Quantum Regime? | null | J.Stat.Phys. 124, 15 (2006) | 10.1007/s10955-006-9151-6 | null | quant-ph cond-mat.stat-mech | null | The first in a long series of papers by John T. Lewis,
G. W. Ford and the present author, considered the problem of the most general
coupling of a quantum particle to a linear passive heat bath, in the course of
which they derived an exact formula for the free energy of an oscillator
coupled to a heat bath in thermal equilibrium at temperature T. This formula,
and its later extension to three dimensions to incorporate a magnetic field,
has proved to be invaluable in analyzing problems in quantum thermodynamics.
Here, we address the question raised in our title viz. Nernst's third law of
thermodynamics.
| [
{
"version": "v1",
"created": "Wed, 20 Sep 2006 21:32:35 GMT"
}
]
| 2016-09-08T00:00:00 | [
[
"O'Connell",
"R. F.",
""
]
]
|
quant-ph/0609160 | Michele Mosca | W. van Dam, G. M. D'Ariano, A. Ekert, C. Macchiavello and M. Mosca | Optimal quantum circuits for general phase estimation | 4 pages, 3 figures | null | 10.1103/PhysRevLett.98.090501 | null | quant-ph | null | We address the problem of estimating the phase phi given N copies of the
phase rotation gate u(phi). We consider, for the first time, the optimization
of the general case where the circuit consists of an arbitrary input state,
followed by any arrangement of the N phase rotations interspersed with
arbitrary quantum operations, and ending with a POVM. Using the polynomial
method, we show that, in all cases where the measure of quality of the estimate
phi' for phi depends only on the difference phi'-phi, the optimal scheme has a
very simple fixed form. This implies that an optimal general phase estimation
procedure can be found by just optimizing the amplitudes of the initial state.
| [
{
"version": "v1",
"created": "Wed, 20 Sep 2006 21:50:16 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"van Dam",
"W.",
""
],
[
"D'Ariano",
"G. M.",
""
],
[
"Ekert",
"A.",
""
],
[
"Macchiavello",
"C.",
""
],
[
"Mosca",
"M.",
""
]
]
|
quant-ph/0609161 | Marie-No\"elle C\'el\'erier | Marie-No\"elle C\'el\'erier and Laurent Nottale (Observatoire de
Paris-Meudon) | Quantum-classical transition in Scale Relativity | 28 pages, no figure | J.Phys.A37:931-955,2004 | 10.1088/0305-4470/37/3/026 | null | quant-ph | null | The theory of scale relativity provides a new insight into the origin of
fundamental laws in physics. Its application to microphysics allows us to
recover quantum mechanics as mechanics on a non-differentiable (fractal)
spacetime. The Schrodinger and Klein-Gordon equations are demonstrated as
geodesic equations in this framework. A development of the intrinsic properties
of this theory, using the mathematical tool of Hamilton's bi-quaternions, leads
us to a derivation of the Dirac equation within the scale-relativity paradigm.
The complex form of the wavefunction in the Schrodinger and Klein-Gordon
equations follows from the non-differentiability of the geometry, since it
involves a breaking of the invariance under the reflection symmetry on the
(proper) time differential element (ds <-> - ds). This mechanism is generalized
for obtaining the bi-quaternionic nature of the Dirac spinor by adding a
further symmetry breaking due to non-differentiability, namely the differential
coordinate reflection symmetry (dx^mu <-> - dx^mu) and by requiring invariance
under parity and time inversion. The Pauli equation is recovered as a
non-relativistic-motion approximation of the Dirac equation.
| [
{
"version": "v1",
"created": "Thu, 21 Sep 2006 10:55:44 GMT"
}
]
| 2011-07-13T00:00:00 | [
[
"Célérier",
"Marie-Noëlle",
"",
"Observatoire de\n Paris-Meudon"
],
[
"Nottale",
"Laurent",
"",
"Observatoire de\n Paris-Meudon"
]
]
|
quant-ph/0609162 | Dominik Janzing | Dominik Janzing and Bastian Steudel | A Quantum Broadcasting Problem in Classical Low Power Signal Processing | 28 pages, latex | null | 10.1103/PhysRevA.75.022309 | null | quant-ph | null | We pose a problem called ``broadcasting Holevo-information'': given an
unknown state taken from an ensemble, the task is to generate a bipartite state
transfering as much Holevo-information to each copy as possible.
We argue that upper bounds on the average information over both copies imply
lower bounds on the quantum capacity required to send the ensemble without
information loss. This is because a channel with zero quantum capacity has a
unitary extension transfering at least as much information to its environment
as it transfers to the output.
For an ensemble being the time orbit of a pure state under a Hamiltonian
evolution, we derive such a bound on the required quantum capacity in terms of
properties of the input and output energy distribution. Moreover, we discuss
relations between the broadcasting problem and entropy power inequalities.
The broadcasting problem arises when a signal should be transmitted by a
time-invariant device such that the outgoing signal has the same timing
information as the incoming signal had. Based on previous results we argue that
this establishes a link between quantum information theory and the theory of
low power computing because the loss of timing information implies loss of free
energy.
| [
{
"version": "v1",
"created": "Thu, 21 Sep 2006 14:48:48 GMT"
}
]
| 2013-05-29T00:00:00 | [
[
"Janzing",
"Dominik",
""
],
[
"Steudel",
"Bastian",
""
]
]
|
quant-ph/0609163 | Hrvoje Nikolic | H. Nikolic | Quantum mechanics: Myths and facts | 51 pages, pedagogic review, revised, new references, to appear in
Found. Phys | Found.Phys.37:1563-1611,2007 | 10.1007/s10701-007-9176-y | null | quant-ph gr-qc hep-th physics.ed-ph | null | A common understanding of quantum mechanics (QM) among students and practical
users is often plagued by a number of "myths", that is, widely accepted claims
on which there is not really a general consensus among experts in foundations
of QM. These myths include wave-particle duality, time-energy uncertainty
relation, fundamental randomness, the absence of measurement-independent
reality, locality of QM, nonlocality of QM, the existence of well-defined
relativistic QM, the claims that quantum field theory (QFT) solves the problems
of relativistic QM or that QFT is a theory of particles, as well as myths on
black-hole entropy. The fact is that the existence of various theoretical and
interpretational ambiguities underlying these myths does not yet allow us to
accept them as proven facts. I review the main arguments and counterarguments
lying behind these myths and conclude that QM is still a
not-yet-completely-understood theory open to further fundamental research.
| [
{
"version": "v1",
"created": "Thu, 21 Sep 2006 15:01:43 GMT"
},
{
"version": "v2",
"created": "Mon, 16 Apr 2007 11:59:20 GMT"
}
]
| 2008-11-26T00:00:00 | [
[
"Nikolic",
"H.",
""
]
]
|
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