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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
quant-ph/0611158 | Shao-Ming Fei | Xiu-Hong Gao, Shao-Ming Fei, Ke Wu | Lower Bounds of Concurrence for Tripartite Quantum Systems | 10 pages | Phys. Rev. A 74 (Rapid Commun.)(2006)050303 | 10.1103/PhysRevA.74.050303 | null | quant-ph | null | We derive an analytical lower bound for the concurrence of tripartite quantum
mixed states. A functional relation is established relating concurrence and the
generalized partial transpositions.
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 22:21:18 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Gao",
"Xiu-Hong",
""
],
[
"Fei",
"Shao-Ming",
""
],
[
"Wu",
"Ke",
""
]
]
|
quant-ph/0611159 | Lan Zhou | Lan Zhou, Jing Lu, C. P. Sun | Coherent control of photon transmission : slowing light in coupled
resonator waveguide doped with $\Lambda $ Atoms | 10 pages, 6 figures | Phys. Rev. A 76, 012313 (2007) | 10.1103/PhysRevA.76.012313 | null | quant-ph | null | In this paper, we propose and study a hybrid mechanism for coherent
transmission of photons in the coupled resonator optical waveguide (CROW) by
incorporating the electromagnetically induced transparency (EIT) effect into
the controllable band gap structure of the CROW. Here, the configuration setup
of system consists of a CROW with homogeneous couplings and the artificial
atoms with $\Lambda$-type three levels doped in each cavity. The roles of three
levels are completely considered based on a mean field approach where the
collection of three-level atoms collectively behave as two-mode spin waves. We
show that the dynamics of low excitations of atomic ensemble can be effectively
described by an coupling boson model. The exactly solutions show that the light
pulses can be stopped and stored coherently by adiabatically controlling the
classical field.
| [
{
"version": "v1",
"created": "Wed, 15 Nov 2006 05:32:24 GMT"
},
{
"version": "v2",
"created": "Thu, 1 Feb 2007 06:06:32 GMT"
},
{
"version": "v3",
"created": "Fri, 9 Mar 2007 07:07:32 GMT"
},
{
"version": "v4",
"created": "Wed, 13 Jun 2007 03:23:06 GMT"
},
{
"version": "v5",
"created": "Sat, 21 Jul 2007 01:27:21 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Zhou",
"Lan",
""
],
[
"Lu",
"Jing",
""
],
[
"Sun",
"C. P.",
""
]
]
|
quant-ph/0611160 | Keisuke Fujii | Keisuke Fujii, Katsuji Yamamoto | Fault-tolerant Quantum Computation with Highly Verified Logical Cluster
States | 4pages, 7figures | null | null | null | quant-ph | null | We investigate a scheme of fault-tolerant quantum computation based on the
cluster model. Logical qubits are encoded by a suitable code such as the
Steane's 7-qubit code. Cluster states of logical qubits are prepared by
post-selection through verification at high fidelity level, where the
unsuccessful ones are discarded without recovery operation. Then, gate
operations are implemented by transversal measurements on the prepared logical
cluster states. The noise threshold is improved significantly by making the
high fidelity preparation and transversal measurement. It is estimated to be
about 3% by a numerical simulation.
| [
{
"version": "v1",
"created": "Wed, 15 Nov 2006 10:01:33 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Fujii",
"Keisuke",
""
],
[
"Yamamoto",
"Katsuji",
""
]
]
|
quant-ph/0611161 | R. Srikanth | Subhashish Banerjee and R. Srikanth | Geometric Phase of a qubit interacting with a squeezed-thermal bath | Accepted for publication in Eur. Phys. J. D; slightly abridged
version of v2; 10 pages, 12 figures | Eur. Phys. J. D 46, 335 (2008) | 10.1140/epjd/e2007-00291-5 | null | quant-ph cond-mat.other | null | We study the geometric phase of an open two-level quantum system under the
influence of a squeezed, thermal environment for both non-dissipative as well
as dissipative system-environment interactions. In the non-dissipative case,
squeezing is found to have a similar influence as temperature, of suppressing
geometric phase, while in the dissipative case, squeezing tends to counteract
the suppressive influence of temperature in certain regimes. Thus, an
interesting feature that emerges from our work is the contrast in the interplay
between squeezing and thermal effects in non-dissipative and dissipative
interactions. This can be useful for the practical implementation of geometric
quantum information processing. By interpreting the open quantum effects as
noisy channels, we make the connection between geometric phase and quantum
noise processes familiar from quantum information theory.
| [
{
"version": "v1",
"created": "Wed, 15 Nov 2006 11:33:47 GMT"
},
{
"version": "v2",
"created": "Wed, 5 Sep 2007 09:58:41 GMT"
},
{
"version": "v3",
"created": "Mon, 1 Oct 2007 13:33:01 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Banerjee",
"Subhashish",
""
],
[
"Srikanth",
"R.",
""
]
]
|
quant-ph/0611162 | Henning Schomerus | Henning Schomerus, Eric Lutz | Nonexponential decoherence and momentum subdiffusion in a quantum L\'evy
kicked rotator | 4 pages, 1 figure | Phys. Rev. Lett. 98, 260401 (2007) | 10.1103/PhysRevLett.98.260401 | null | quant-ph cond-mat.mes-hall nlin.CD | null | We investigate decoherence in the quantum kicked rotator (modelling cold
atoms in a pulsed optical field) subjected to noise with power-law tail
waiting-time distributions of variable exponent (Levy noise). We demonstrate
the existence of a regime of nonexponential decoherence where the notion of a
decoherence rate is ill-defined. In this regime, dynamical localization is
never fully destroyed, indicating that the dynamics of the quantum system never
reaches the classical limit. We show that this leads to quantum subdiffusion of
the momentum, which should be observable in an experiment.
| [
{
"version": "v1",
"created": "Wed, 15 Nov 2006 17:39:40 GMT"
}
]
| 2007-08-01T00:00:00 | [
[
"Schomerus",
"Henning",
""
],
[
"Lutz",
"Eric",
""
]
]
|
quant-ph/0611163 | L. S. Schulman | L. S. Schulman and B. Gaveau | Ratcheting up energy by means of measurement | To appear in Phys. Rev. Lett | Phys. Rev. Lett. 97, 240405 (2006) | 10.1103/PhysRevLett.97.240405 | null | quant-ph | null | The destruction of quantum coherence can pump energy into a system. For our
examples this is paradoxical since the destroyed correlations are ordinarily
considered negligible. Mathematically the explanation is straightforward and
physically one can identify the degrees of freedom supplying this energy.
Nevertheless, the energy input can be calculated without specific reference to
those degrees of freedom.
| [
{
"version": "v1",
"created": "Wed, 15 Nov 2006 12:38:55 GMT"
}
]
| 2007-11-08T00:00:00 | [
[
"Schulman",
"L. S.",
""
],
[
"Gaveau",
"B.",
""
]
]
|
quant-ph/0611164 | Stefano Longhi | Stefano Longhi | Non-exponential decay via tunneling in tight-binding lattices and the
optical Zeno effect | null | S. Longhi, Phys. Rev. Lett. 97, 110402 (2006) | 10.1103/PhysRevLett.97.110402 | null | quant-ph | null | An exactly-solvable model for the decay of a metastable state coupled to a
semi-infinite tight-binding lattice, showing large deviations from exponential
decay in the strong coupling regime, is presented. An optical realization of
the lattice model, based on discrete diffraction in a semi-infinite array of
tunneling-coupled optical waveguides, is proposed to test non-exponential decay
and for the observation of an optical analog of the quantum Zeno effect.
| [
{
"version": "v1",
"created": "Wed, 15 Nov 2006 15:22:55 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Longhi",
"Stefano",
""
]
]
|
quant-ph/0611165 | Nicolas Sangouard | Nicolas Sangouard, Christoph Simon, Mikael Afzelius, Nicolas Gisin | Analysis of a quantum memory for photons based on controlled reversible
inhomogeneous broadening | 9 pages, 4 figures (Accepted for publication in Phys. Rev. A) | Phys. Rev. A 75, 032327 (2007) | 10.1103/PhysRevA.75.032327 | null | quant-ph | null | We present a detailed analysis of a quantum memory for photons based on
controlled and reversible inhomogeneous broadening (CRIB). The explicit
solution of the equations of motion is obtained in the weak excitation regime,
making it possible to gain insight into the dependence of the memory efficiency
on the optical depth, and on the width and shape of the atomic spectral
distributions. We also study a simplified memory protocol which does not
require any optical control fields.
| [
{
"version": "v1",
"created": "Wed, 15 Nov 2006 16:15:35 GMT"
},
{
"version": "v2",
"created": "Tue, 30 Jan 2007 10:58:44 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Sangouard",
"Nicolas",
""
],
[
"Simon",
"Christoph",
""
],
[
"Afzelius",
"Mikael",
""
],
[
"Gisin",
"Nicolas",
""
]
]
|
quant-ph/0611166 | Simone Montangero | Simone Montangero, Tommaso Calarco, Rosario Fazio | Robust optimal quantum gates for Josephson charge qubits | 4 pages, 4 figures | Phys. Rev. Lett. 99, 170501 (2007) | 10.1103/PhysRevLett.99.170501 | null | quant-ph cond-mat.supr-con | null | Quantum optimal control theory allows to design accurate quantum gates. We
employ it to design high-fidelity two-bit gates for Josephson charge qubits in
the presence of both leakage and noise. Our protocol considerably increases the
fidelity of the gate and, more important, it is quite robust in the disruptive
presence of 1/f noise. The improvement in the gate performances discussed in
this work (errors of the order of 10^{-3}-10^{-4} in realistic cases) allows to
cross the fault tolerance threshold.
| [
{
"version": "v1",
"created": "Wed, 15 Nov 2006 17:25:12 GMT"
},
{
"version": "v2",
"created": "Wed, 5 Sep 2007 12:09:25 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Montangero",
"Simone",
""
],
[
"Calarco",
"Tommaso",
""
],
[
"Fazio",
"Rosario",
""
]
]
|
quant-ph/0611167 | Stefano Pirandola | Stefano Pirandola, Stefano Mancini, Seth Lloyd, and Samuel L.
Braunstein | Continuous Variable Quantum Cryptography using Two-Way Quantum
Communication | 12 pages, 7 figures, REVTeX | Nature Physics 4, 726 - 730 (2008) | 10.1038/nphys1018 | null | quant-ph cs.CR cs.IT math.IT physics.optics | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Quantum cryptography has been recently extended to continuous variable
systems, e.g., the bosonic modes of the electromagnetic field. In particular,
several cryptographic protocols have been proposed and experimentally
implemented using bosonic modes with Gaussian statistics. Such protocols have
shown the possibility of reaching very high secret-key rates, even in the
presence of strong losses in the quantum communication channel. Despite this
robustness to loss, their security can be affected by more general attacks
where extra Gaussian noise is introduced by the eavesdropper. In this general
scenario we show a "hardware solution" for enhancing the security thresholds of
these protocols. This is possible by extending them to a two-way quantum
communication where subsequent uses of the quantum channel are suitably
combined. In the resulting two-way schemes, one of the honest parties assists
the secret encoding of the other with the chance of a non-trivial superadditive
enhancement of the security thresholds. Such results enable the extension of
quantum cryptography to more complex quantum communications.
| [
{
"version": "v1",
"created": "Wed, 15 Nov 2006 19:00:58 GMT"
},
{
"version": "v2",
"created": "Sat, 1 Sep 2007 01:12:41 GMT"
},
{
"version": "v3",
"created": "Wed, 3 Dec 2008 00:58:40 GMT"
}
]
| 2008-12-03T00:00:00 | [
[
"Pirandola",
"Stefano",
""
],
[
"Mancini",
"Stefano",
""
],
[
"Lloyd",
"Seth",
""
],
[
"Braunstein",
"Samuel L.",
""
]
]
|
quant-ph/0611168 | Vladimir Manko | V.N.Chernega, V.I.Man'ko | Qubit portrait of qudit states and Bell inequalities | 21 pages, 2 figures, to be published in J. Russ. Laser Res | null | null | null | quant-ph | null | A linear map of qudit tomogram onto qubit tomogram (qubit portrait) is
proposed as a characteristics of the qudit state. Using the qubit portrait
method the Bell inequalities for two qubits and two qutrits are discussed in
framework of probability representation of quantum mechanics. Semigroup of
stochastic matrices is associated with tomographic probability distributions of
qubit and qutrit states. Bell-like inequalities are studied using the semigroup
of stochastic matrices. The qudit-qubit map of tomographic probability
distributions is discussed as ansatz to provide a necessary condition for
separability of quantum states.
| [
{
"version": "v1",
"created": "Wed, 15 Nov 2006 17:43:58 GMT"
},
{
"version": "v2",
"created": "Fri, 17 Nov 2006 16:56:22 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Chernega",
"V. N.",
""
],
[
"Man'ko",
"V. I.",
""
]
]
|
quant-ph/0611169 | J\"org G\"otte | J. B. Goette, S. Franke-Arnold, R. Zambrini and Stephen M. Barnett | Quantum Formulation of Fractional Orbital Angular Momentum | 14 pages, 6 figure (figures are of low quality due to jpeg2ps
conversion), submitted to J Mod Opt special issue for the Photon 06
conference | null | 10.1080/09500340601156827 | null | quant-ph | null | The quantum theory of rotation angles (S. M. Barnett and D. T. Pegg, Phys.
Rev. A, 41, 3427-3425 (1990)) is generalised to non-integer values of the
orbital angular momentum. This requires the introduction of an additional
parameter, the orientation of a phase discontinuity associated with fractional
values of the orbital angular momentum. We apply our formalism to the
propagation of light modes with fractional orbital angular momentum in the
paraxial and non-paraxial regime.
| [
{
"version": "v1",
"created": "Wed, 15 Nov 2006 22:11:49 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Goette",
"J. B.",
""
],
[
"Franke-Arnold",
"S.",
""
],
[
"Zambrini",
"R.",
""
],
[
"Barnett",
"Stephen M.",
""
]
]
|
quant-ph/0611170 | Hongwei Yu | Jialin Zhang, Hongwei Yu | Entanglement generation in atoms immersed in a thermal bath of external
quantum scalar fields with a boundary | 19 pages, 4 figures, to be published in PRA | Phys.Rev. A75 (2007) 012101 | 10.1103/PhysRevA.75.012101 | null | quant-ph hep-th | null | We examine the entanglement creation between two mutually independent
two-level atoms immersed in a thermal bath of quantum scalar fields in the
presence of a perfectly reflecting plane boundary. With the help of the master
equation that describes the evolution in time of the atom subsystem obtained,
in the weak-coupling limit, by tracing over environment (scalar fields) degrees
of freedom, we find that the presence of the boundary may play a significant
role in the entanglement creation in some circumstances and the new parameter,
the distance of the atoms from the boundary, besides the bath temperature and
the separation between the atoms, gives us more freedom in manipulating
entanglement generation. Remarkably, the final remaining entanglement in the
equilibrium state is independent of the presence of the boundary.
| [
{
"version": "v1",
"created": "Thu, 16 Nov 2006 01:46:31 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Zhang",
"Jialin",
""
],
[
"Yu",
"Hongwei",
""
]
]
|
quant-ph/0611171 | Yuma Kinoshita | Yuma Kinoshita, Ryo Namiki, Takashi Yamamoto, Masato Koashi, and
Nobuyuki Imoto | Selective entanglement breaking | 6 pages, 2 figures | null | 10.1103/PhysRevA.75.032307 | null | quant-ph | null | We discuss the cases where local decoherence selectively degrades one type of
entanglement more than other types. A typical case is called state ordering
change, in which two input states with different amounts of entanglement
undergoes a local decoherence and the state with the larger entanglement
results in an output state with less entanglement than the other output state.
We are also interested in a special case where the state with the larger
entanglement evolves to a separable state while the other output state is still
entangled, which we call selective entanglement breaking. For three-level or
larger systems, it is easy to find examples of the state ordering change and
the selective entanglement breaking, but for two-level systems it is not
trivial whether such situations exist. We present a new strategy to construct
examples of two-qubit states exhibiting the selective entanglement breaking
regardless of entanglement measure. We also give a more striking example of the
selective entanglement breaking in which the less entangled input state has
only an infinitesimal amount of entanglement.
| [
{
"version": "v1",
"created": "Thu, 16 Nov 2006 06:07:18 GMT"
}
]
| 2013-05-29T00:00:00 | [
[
"Kinoshita",
"Yuma",
""
],
[
"Namiki",
"Ryo",
""
],
[
"Yamamoto",
"Takashi",
""
],
[
"Koashi",
"Masato",
""
],
[
"Imoto",
"Nobuyuki",
""
]
]
|
quant-ph/0611172 | Ye Yeo | Chunfeng Wu, Ye Yeo, L. C. Kwek, and C. H. Oh | Quantum nonlocality of four-qubit entangled states | 13 pages, 1 figure | null | 10.1103/PhysRevA.75.032332 | null | quant-ph | null | Quantum nonlocality of several four-qubit states is investigated by
constructing a new Bell inequality. These include the
Greenberger-Zeilinger-Horne (GHZ) state, W state, cluster state, and the state
$|\chi>$ that has been recently proposed in [PRL, {\bf 96}, 060502 (2006)]. The
Bell inequality is optimally violated by $|\chi>$ but not violated by the GHZ
state. The cluster state also violates the Bell inequality though not
optimally. The state $|\chi>$ can thus be discriminated from the cluster state
by using the inequality. Different aspects of four-partite entanglement are
also studied by considering the usefulness of a family of four-qubit mixed
states as resources for two-qubit teleportation. Our results generalize those
in [PRL, {\bf 72}, 797 (1994)].
| [
{
"version": "v1",
"created": "Thu, 16 Nov 2006 06:53:26 GMT"
}
]
| 2013-05-29T00:00:00 | [
[
"Wu",
"Chunfeng",
""
],
[
"Yeo",
"Ye",
""
],
[
"Kwek",
"L. C.",
""
],
[
"Oh",
"C. H.",
""
]
]
|
quant-ph/0611173 | Erez Boukobza Dr. | E. Boukobza D. J. Tannor | Thermodynamics of bipartite systems: Application to light-matter
interactions | 12 pages, 1 figure. PRA (in press) | null | null | null | quant-ph | null | Heat and work for quantum systems governed by dissipative master equations
with a time-dependent driving field were introduced in the pioneering work of
Alicki [J. Phys. A 12, L103 (1979)]. Alicki's work was in the Schroedinger
picture; here we extend these definitions to the Heisenberg and interaction
pictures. We show that in order to avoid consistency problems, the full time
derivatives in the definitions for heat flux and power (work flux) should be
replaced by partial time derivatives. We also present an alternative approach
to the partitioning of the energy flux which differs from that of Alicki in
that the instantaneous interaction energy with the external field is not
included directly. We then proceed to generalize Alicki's definition of power
by replacing the original system and its external driving field with a larger,
bipartite system, governed by a time-independent Hamiltonian. Using the
definition of heat flux and the generalized definition of power, we derive the
first law of thermodynamics in differential form, both for the full bipartite
system and the partially traced subsystems. Although the second law (Clausius
formulation) is satisfied for the full bipartite system, we find that in
general there is no rigorous formulation of the second law for the partially
traced subsystem unless certain additional requirements are met. Once these
requirements are satisfied, however, both the Carnot and the Clausius
formulations of the second law are satisfied. We illustrate this thermodynamic
analysis on both the simple Jaynes-Cummings model (JCM) and an extended
dissipative Jaynes-Cummings model (ED-JCM), which is a model for a quantum
amplifier.
| [
{
"version": "v1",
"created": "Thu, 16 Nov 2006 08:29:05 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Tannor",
"E. Boukobza D. J.",
""
]
]
|
quant-ph/0611174 | Th. Busch | K. Deasy, Th. Busch, Y. Niu, S. Gong, S. Jin and S. Nic Chormaic | Controlled Creation of Spatial Superposition States for Single Atoms | 5 pages, 4 figures | null | null | null | quant-ph | null | We present a method for the controlled and robust generation of spatial
superposition states of single atoms in micro-traps. Using a counter-intuitive
positioning sequence for the individual potentials and appropriately chosen
trapping frequencies, we show that it is possible to selectively create two
different orthogonal superposition states, which can in turn be used for
quantum information purposes.
| [
{
"version": "v1",
"created": "Thu, 16 Nov 2006 10:41:46 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Deasy",
"K.",
""
],
[
"Busch",
"Th.",
""
],
[
"Niu",
"Y.",
""
],
[
"Gong",
"S.",
""
],
[
"Jin",
"S.",
""
],
[
"Chormaic",
"S. Nic",
""
]
]
|
quant-ph/0611175 | Erez Boukobza Dr. | E. Boukobza D. J. Tannor | Thermodynamic analysis of quantum light amplification | 19 pages, 6 figures. PRA (in press) | null | null | null | quant-ph | null | Thermodynamics of a three-level maser was studied in the pioneering work of
Scovil and Schulz-DuBois [Phys. Rev. Lett. 2, 262 (1959)]. In this work we
consider the same three-level model, but treat both the matter and light
quantum mechanically. Specifically, we analyze an extended (three-level)
dissipative Jaynes-Cummings model (ED-JCM) within the framework of a quantum
heat engine, using novel formulas for heat flux and power in bipartite systems
introduced in our previous work [E. Boukobza and D. J. Tannor, PRA (in press)].
Amplification of the selected cavity mode occurs even in this simple model, as
seen by a positive steady state power. However, initial field coherence is
lost, as seen by the decaying off-diagonal field density matrix elements, and
by the Husimi-Kano Q function. We show that after an initial transient time the
field's entropy rises linearly during the operation of the engine, which we
attribute to the dissipative nature of the evolution and not to matter-field
entanglement. We show that the second law of thermodynamics is satisfied in two
formulations (Clausius, Carnot) and that the efficiency of the ED-JCM heat
engine agrees with that defined intuitively by Scovil and Schulz-DuBois.
Finally, we compare the steady state heat flux and power of the fully quantum
model with the semiclassical counterpart of the ED-JCM, and derive the engine
efficiency formula of Scovil and Schulz-DuBois analytically from fundamental
thermodynamic fluxes.
| [
{
"version": "v1",
"created": "Thu, 16 Nov 2006 09:38:58 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Tannor",
"E. Boukobza D. J.",
""
]
]
|
quant-ph/0611176 | Milos V. Lokajicek | Milos V. Lokajicek | Schroedinger and Hamilton-Jacobi equations | 7 pages | null | null | null | quant-ph | null | Time-dependent Schroedinger equation represents the basis of any
quantum-theoretical approach. The question concerning its proper content in
comparison to the classical physics has not been, however, fully answered until
now. It will be shown that there is one-to-one physical correspondence between
basic solutions (represented always by one Hamiltonian eigenfunction only) and
classical ones, as the non-zero quantum potential has not any physical sense,
representing only the "numerical" difference between Hamilton principal
function and the phase of corresponding wave function in the case of
non-inertial motion. Possible interpretation of superposition solutions will be
then discussed in the light of this fact. And also different interpretation
alternatives of the quantum-mechanical model will be newly analyzed and new
attitude to them will be reasoned.
| [
{
"version": "v1",
"created": "Thu, 16 Nov 2006 10:22:42 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Lokajicek",
"Milos V.",
""
]
]
|
quant-ph/0611177 | Guo-Qiang Zhu | Guo-Qiang Zhu and Xiaoguang Wang | Quantum Dynamics of Bound Entangled States | 5 pages, 3 figures | null | null | null | quant-ph | null | By using the partial transpose and realignment method,we study the time
evolution of the bound entanglement under the bilinear-biquadratic Hamiltonian.
For the initial Horodecki's bound entangled state, it keeps bound entangled for
some time, while for the initial bound entangled states constructed from the
unextendable product basis, they become free once the time evolution begins.
The time evolution provides a new way to construct bound entangled states, and
also gives a method to free bound entanglement.
| [
{
"version": "v1",
"created": "Thu, 16 Nov 2006 11:29:51 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Zhu",
"Guo-Qiang",
""
],
[
"Wang",
"Xiaoguang",
""
]
]
|
quant-ph/0611178 | Bo Wang | Bo Wang, Yanxu Han, Jintao Xiao, Xudong Yang, Chunhong Zhang, Hai
Wang, Min Xiao, and Kunchi Peng | Preparation and Determination of Spin-Polarized States in
Multi-Zeeman-sublevel Atoms | 17pages, 4figures, Submit to Physical Review Letters | null | 10.1103/PhysRevA.75.051801 | null | quant-ph | null | We demonstrate a simple technique to prepare and determine the desired
internal quantum states in multi-Zeeman-sublevel atoms. By choosing appropriate
coupling and pumping laser beams, atoms can be easily prepared in a desired
Zeeman sublevel with high purity or in any chosen ground-state population
distributions. The population distributions or state purities of such prepared
atomic states can be determined by using a weak, circularly-polarized probe
beam due to differences in transition strengths among different Zeeman
sublevels. Preparing well-defined internal quantum states in
multi-Zeeman-sublevel atoms (or spin-polarized quantum-state engineering) will
be very important in demonstrating many interesting effects in quantum
information processing with multi-level atomic systems.
| [
{
"version": "v1",
"created": "Thu, 16 Nov 2006 12:52:21 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Wang",
"Bo",
""
],
[
"Han",
"Yanxu",
""
],
[
"Xiao",
"Jintao",
""
],
[
"Yang",
"Xudong",
""
],
[
"Zhang",
"Chunhong",
""
],
[
"Wang",
"Hai",
""
],
[
"Xiao",
"Min",
""
],
[
"Peng",
"Kunchi",
""
]
]
|
quant-ph/0611179 | Andrea Aiello | A. Aiello, G. Puentes, and J. P. Woerdman | Linear optics and quantum maps | 13 pages, 8 figures | null | 10.1103/PhysRevA.76.032323 | null | quant-ph | null | We present a theoretical analysis of the connection between classical
polarization optics and quantum mechanics of two-level systems. First, we
review the matrix formalism of classical polarization optics from a quantum
information perspective. In this manner the passage from the
Stokes-Jones-Mueller description of classical optical processes to the
representation of one- and two-qubit quantum operations, becomes
straightforward. Second, as a practical application of our
classical-\emph{vs}-quantum formalism, we show how two-qubit maximally
entangled mixed states (MEMS), can be generated by using polarization and
spatial modes of photons generated via spontaneous parametric down conversion.
| [
{
"version": "v1",
"created": "Thu, 16 Nov 2006 15:58:39 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Aiello",
"A.",
""
],
[
"Puentes",
"G.",
""
],
[
"Woerdman",
"J. P.",
""
]
]
|
quant-ph/0611180 | Rubens Ramos Viana | Rubens Viana Ramos | The Relation between Disentangled States and Algorithmic Information
Theory | 3 pages | null | null | null | quant-ph | null | In this short communication it is proposed the general form of a n-qubit
disentangled state as a irreducible sentence, in the sense explained by the
algorithmic information theory, whose length increases in a non-polynomial way
when the number of qubits increases.
| [
{
"version": "v1",
"created": "Thu, 16 Nov 2006 18:17:03 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Ramos",
"Rubens Viana",
""
]
]
|
quant-ph/0611181 | Alexander I. Lvovsky | Frank Vewinger, Juergen Appel, Eden Figueroa, A. I. Lvovsky | Adiabatic frequency conversion of quantum optical information in atomic
vapor | null | Optics Letters 32, 2771 (2007) | 10.1364/OL.32.002771 | null | quant-ph | null | We experimentally demonstrate a quantum communication protocol that enables
frequency conversion and routing of quantum optical information in an adiabatic
and thus robust way. The protocol is based on electromagnetically-induced
transparency in systems with multiple excited levels: transfer and/or
distribution of optical states between different signal modes is implemented by
adiabatically changing the control fields. The proof-of-principle experiment is
performed using the hyperfine levels of the rubidium D1 line.
| [
{
"version": "v1",
"created": "Thu, 16 Nov 2006 23:00:27 GMT"
},
{
"version": "v2",
"created": "Sat, 26 May 2007 05:57:56 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Vewinger",
"Frank",
""
],
[
"Appel",
"Juergen",
""
],
[
"Figueroa",
"Eden",
""
],
[
"Lvovsky",
"A. I.",
""
]
]
|
quant-ph/0611182 | Yoshiyuki Tsuda | Yoshiyuki Tsuda | Bhattacharyya inequality for quantum state estimation | 22 pages, no figure | J. Phys. A: Math. Theor. 40 793-810 (2007) | 10.1088/1751-8113/40/4/015 | null | quant-ph | null | Using higher-order derivative with respect to the parameter, we will give
lower bounds for variance of unbiased estimators in quantum estimation
problems. This is a quantum version of the Bhattacharyya inequality in the
classical statistical estimation. Because of non-commutativity of operator
multiplication, we obtain three different types of lower bounds; Type S, Type R
and Type L. If the parameter is a real number, the Type S bound is useful. If
the parameter is complex, the Type R and L bounds are useful. As an
application, we will consider estimation of polynomials of the complex
amplitude of the quantum Gaussian state. For the case where the amplitude lies
in the real axis, a uniformly optimum estimator for the square of the amplitude
will be derived using the Type S bound. It will be shown that there is no
unbiased estimator uniformly optimum as a polynomial of annihilation and/or
creation operators for the cube of the amplitude. For the case where the
amplitude does not necessarily lie in the real axis, uniformly optimum
estimators for holomorphic, antiholomorphic and real-valued polynomials of the
amplitude will be derived. Those estimators for the holomorphic and real-valued
cases attains the Type R bound, and those for the antiholomorphic and
real-valued cases attains the Type L bound. This article clarifies what is the
best method to measure energy of laser.
| [
{
"version": "v1",
"created": "Fri, 17 Nov 2006 03:12:01 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Tsuda",
"Yoshiyuki",
""
]
]
|
quant-ph/0611183 | Ramazan Sever | Sameer M. Ikhdair and Ramazan Sever | Exact Polynomial Eigensolutions of the Schrodinger Equation for the
Pseudoharmonic Potential | 10 pages | Int. J. of Molecular Structure(THEOCHEM) 806, 155(2007 | null | null | quant-ph | null | The polynomial solution of the Schrodinger equation for the Pseudoharmonic
potential is found for any arbitrary angular momentum $l$. The exact
bound-state energy eigenvalues and the corresponding eigen functions are
analytically calculated. The energy states for several diatomic molecular
systems are calculated numerically for various principal and angular quantum
numbers. By a proper transformation, this problem is also solved very simply by
using the known eigensolutions of anharmonic oscillator potential.
| [
{
"version": "v1",
"created": "Fri, 17 Nov 2006 08:41:28 GMT"
},
{
"version": "v2",
"created": "Mon, 4 Dec 2006 13:26:18 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Ikhdair",
"Sameer M.",
""
],
[
"Sever",
"Ramazan",
""
]
]
|
quant-ph/0611184 | Jie Yang | Jie Yang, Hao Yuan and Zhan-jun Zhang | Comments on 'Teleportation of two quNit entanglement: Exploiting local
resources'and 'Reply to Yang et al.'s comment' | 5 pages, 1 table, no figures | null | null | null | quant-ph | null | This paper includes two comments. The first one is a comment on
'Teleportation of two quNit entanglement: Exploiting local resources'. Two
different efficient methods are presented to modify some details of N. Ba An's
protocol, so that teleportation of two quNit entanglement can be successfully
achieved in terms of the revised N. Ba An's protocol. The second one is a
comment on 'Reply to Yang et al.'s comment'.
| [
{
"version": "v1",
"created": "Fri, 17 Nov 2006 09:35:24 GMT"
},
{
"version": "v2",
"created": "Sun, 24 Dec 2006 15:20:54 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Yang",
"Jie",
""
],
[
"Yuan",
"Hao",
""
],
[
"Zhang",
"Zhan-jun",
""
]
]
|
quant-ph/0611185 | Jacques Vigue | Marion Jacquey (LCAR), Alain Miffre (LCAR, LASIM), Matthias B\"uchner
(LCAR), G\'erard Tr\'enec (LCAR), Jacques Vigu\'e (LCAR) | Test of the isotopic and velocity selectivity of a lithium atom
interferometer by magnetic dephasing | null | null | 10.1209/0295-5075/77/20007 | null | quant-ph | null | A magnetic field gradient applied to an atom interferometer induces a
$M$-dependent phase shift which results in a series of decays and revivals of
the fringe visibility. Using our lithium atom interferometer based on Bragg
laser diffraction, we have measured the fringe visibility as a function of the
applied gradient. We have thus tested the isotopic selectivity of the
interferometer, the velocity selective character of Bragg diffraction for
different diffraction orders as well as the effect of optical pumping of the
incoming atoms. All these observations are qualitatively understood but a
quantitative analysis requires a complete model of the interferometer.
| [
{
"version": "v1",
"created": "Fri, 17 Nov 2006 10:20:15 GMT"
}
]
| 2016-08-16T00:00:00 | [
[
"Jacquey",
"Marion",
"",
"LCAR"
],
[
"Miffre",
"Alain",
"",
"LCAR, LASIM"
],
[
"Büchner",
"Matthias",
"",
"LCAR"
],
[
"Trénec",
"Gérard",
"",
"LCAR"
],
[
"Vigué",
"Jacques",
"",
"LCAR"
]
]
|
quant-ph/0611186 | Mark Tame | M. S. Tame, R. Prevedel, M. Paternostro, P. B\"ohi, M. S. Kim and A.
Zeilinger | Experimental Realization of Deutsch's Algorithm in a One-way Quantum
Computer | 4 pages, 4 figures, RevTeX 4 | Phys. Rev. Lett. 98, 140501 (2007) | 10.1103/PhysRevLett.98.140501 | null | quant-ph | null | We report the first experimental demonstration of an all-optical one-way
implementation of Deutsch's quantum algorithm on a four-qubit cluster state.
All the possible configurations of a balanced or constant function acting on a
two-qubit register are realized within the measurement-based model for quantum
computation. The experimental results are in excellent agreement with the
theoretical model, therefore demonstrating the successful performance of the
algorithm.
| [
{
"version": "v1",
"created": "Fri, 17 Nov 2006 10:57:09 GMT"
},
{
"version": "v2",
"created": "Mon, 2 Apr 2007 17:10:36 GMT"
}
]
| 2013-12-25T00:00:00 | [
[
"Tame",
"M. S.",
""
],
[
"Prevedel",
"R.",
""
],
[
"Paternostro",
"M.",
""
],
[
"Böhi",
"P.",
""
],
[
"Kim",
"M. S.",
""
],
[
"Zeilinger",
"A.",
""
]
]
|
quant-ph/0611187 | Christopher Gordon Timpson | Christopher G Timpson | Philosophical Aspects of Quantum Information Theory | LaTeX; 55pp; 3 figs. Forthcoming in Rickles (ed.) The Ashgate
Companion to the New Philosophy of Physics | null | null | null | quant-ph | null | Quantum information theory represents a rich subject of discussion for those
interested in the philosphical and foundational issues surrounding quantum
mechanics for a simple reason: one can cast its central concerns in terms of a
long-familiar question: How does the quantum world differ from the classical
one? Moreover, deployment of the concepts of information and computation in
novel contexts hints at new (or better) means of understanding quantum
mechanics, and perhaps even invites re-assessment of traditional material
conceptions of the basic nature of the physical world. In this paper I review
some of these philosophical aspects of quantum information theory, begining
with an elementary survey of the theory, seeking to highlight some of the
principles and heuristics involved. We move on to a discussion of the nature
and definition of quantum information and deploy the findings in discussing the
puzzles surrounding teleportation. The final two sections discuss,
respectively, what one might learn from the development of quantum computation
(both about the nature of quantum systems and about the nature of computation)
and consider the impact of quantum information theory on the traditional
foundational questions of quantum mechanics (treating of the views of
Zeilinger, Bub and Fuchs, amongst others).
| [
{
"version": "v1",
"created": "Fri, 17 Nov 2006 14:08:06 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Timpson",
"Christopher G",
""
]
]
|
quant-ph/0611188 | Felipe Fanchini | F. F. Fanchini, J. E. M. Hornos, R. d. J. Napolitano | Continuously decoupling single-qubit operations from a perturbing
thermal bath of scalar bosons | 4 pages, 1 figure | Phys. Rev. A 75, 022329 (2007) | 10.1103/PhysRevA.75.022329 | null | quant-ph | null | We investigate the use of continuously-applied external fields to maximize
the fidelity of quantum logic operations performed on a decohering qubit.
Assuming a known error operator and an environment represented by a scalar
boson field at a finite temperature, we show how decoherence during logical
operations can be efficiently reduced by applying a superposition of two
external vector fields: one rotating orthogonally to the direction of the
other, which remains static. The required field directions, frequency of
rotation and amplitudes to decouple noise dynamically are determined by the
coupling constants and the desired logical operation. We illustrate these
findings numerically for a Hadamard quantum gate and an environment with ohmic
spectral density.
| [
{
"version": "v1",
"created": "Fri, 17 Nov 2006 20:14:07 GMT"
},
{
"version": "v2",
"created": "Wed, 31 Jan 2007 13:19:37 GMT"
}
]
| 2010-05-31T00:00:00 | [
[
"Fanchini",
"F. F.",
""
],
[
"Hornos",
"J. E. M.",
""
],
[
"Napolitano",
"R. d. J.",
""
]
]
|
quant-ph/0611189 | Matthew Grace | Matthew Grace, Constantin Brif, Herschel Rabitz, Ian Walmsley, Robert
Kosut, Daniel A. Lidar | Optimal Control of High-Fidelity Quantum Gates in the Presence of
Decoherence | This paper has been withdrawn as it has been superseded by postings
arXiv:quant-ph/0702147 and arXiv:0712.2935 | null | null | null | quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper has been withdrawn as it has been superseded by postings
arXiv:quant-ph/0702147 and arXiv:0712.2935
| [
{
"version": "v1",
"created": "Fri, 17 Nov 2006 23:22:08 GMT"
},
{
"version": "v2",
"created": "Fri, 2 Feb 2007 16:56:11 GMT"
},
{
"version": "v3",
"created": "Sat, 28 Nov 2009 21:09:59 GMT"
}
]
| 2009-11-28T00:00:00 | [
[
"Grace",
"Matthew",
""
],
[
"Brif",
"Constantin",
""
],
[
"Rabitz",
"Herschel",
""
],
[
"Walmsley",
"Ian",
""
],
[
"Kosut",
"Robert",
""
],
[
"Lidar",
"Daniel A.",
""
]
]
|
quant-ph/0611190 | Ho-Tsang Ng | H. T. Ng, K. Burnett and J. A. Dunningham | Precision measurement with an optical Josephson junction | 6 pages, 1 figure | Phys. Rev. A 75, 063607 (2007) | 10.1103/PhysRevA.75.063607 | null | quant-ph | null | We study a new type of Josephson device, the so-called "optical Josephson
junction" as proposed in Phys. Rev. Lett. {\bf 95}, 170402 (2005). Two
condensates are optically coupled through a waveguide by a pair of Bragg beams.
This optical Josephson junction is analogous to the usual Josephson junction of
two condensates weakly coupled via tunneling. We discuss the use of this
optical Josephson junction, for making precision measurements.
| [
{
"version": "v1",
"created": "Sat, 18 Nov 2006 01:03:21 GMT"
}
]
| 2011-08-02T00:00:00 | [
[
"Ng",
"H. T.",
""
],
[
"Burnett",
"K.",
""
],
[
"Dunningham",
"J. A.",
""
]
]
|
quant-ph/0611191 | Valentin Sokolov V. | Valentin V. Sokolov, Giuliano Benenti, and Giulio Casati | Dynamical chaos versus quantum interference | 15 pages, 1 fugure | null | null | null | quant-ph | null | We discuss the dephasing induced by the internal classical chaotic motion in
the absence of any external environment. To this end a new extension of
fidelity for mixed states is introduced, which we name {\it allegiance}. Such
quantity directly accounts for quantum interference and is measurable in a
Ramsey interferometry experiment. We show that in the semiclassical limit the
decay of the allegiance is exactly expressed, due to the dephasing, in terms of
an appropriate classical correlation function. Our results are derived
analytically for the case of a nonlinear driven oscillator and then numerically
confirmed for the kicked rotor model.
| [
{
"version": "v1",
"created": "Sat, 18 Nov 2006 07:37:56 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Sokolov",
"Valentin V.",
""
],
[
"Benenti",
"Giuliano",
""
],
[
"Casati",
"Giulio",
""
]
]
|
quant-ph/0611192 | Mauro Paternostro | M. Paternostro, M. S. Tame, G. M. Palma, M. S. Kim | Entanglement generation and protection by detuning modulation | 9 pages, 8 figures, RevTeX4 | Phys. Rev. A 74, 052317 (2006) | 10.1103/PhysRevA.74.052317 | null | quant-ph | null | We introduce a protocol for steady-state entanglement generation and
protection based on detuning modulation in the dissipative interaction between
a two-qubit system and a bosonic mode. The protocol is a global-addressing
scheme which only requires control over the system as a whole. We describe a
postselection procedure to project the register state onto a subspace of
maximally entangled states. We also outline how our proposal can be implemented
in a circuit-quantum electrodynamics setup.
| [
{
"version": "v1",
"created": "Mon, 20 Nov 2006 18:33:36 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Paternostro",
"M.",
""
],
[
"Tame",
"M. S.",
""
],
[
"Palma",
"G. M.",
""
],
[
"Kim",
"M. S.",
""
]
]
|
quant-ph/0611193 | Halina Grushevskaya | H. V. Grushevskaya | Relativistic invariant projectors on a complex spinor space and a rule
of polarizations summation in a complex bispinor space | 11pages, talk given at the 5th International Conference
"Boyai-Gauss-Lobachevsky: Methods of Non-Euclidean Geometry in Modern
Physics", Minsk, Belarus,October 10-13, 2006 | null | null | null | quant-ph | null | Relativistic invariant projectors of states in a complex bispinor space on a
complex spinor space are constructed. An expression for sections of bundle with
connection on group SU(4) in an explicit form has been obtained. Within the
framework of the proposed geometrical approach the rule of summation over
polarizations of states in a complex bispinor space has been derived. It has
been shown that states in a complex bispinor space always describe a pair of
Dirac's particles.
| [
{
"version": "v1",
"created": "Mon, 20 Nov 2006 16:57:08 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Grushevskaya",
"H. V.",
""
]
]
|
quant-ph/0611194 | David Zueco | D. Zueco and Ivan Calvo | Bopp operators and phase-space spin dynamics: Application to rotational
quantum brownian motion | Some typos corrected. Published version | J.Phys.A40:4635-4648,2007 | 10.1088/1751-8113/40/17/015 | null | quant-ph cond-mat.stat-mech hep-th | null | As already known for nonrelativistic spinless particles, Bopp operators give
an elegant and simple way to compute the dynamics of quasiprobability
distributions in the phase space formulation of Quantum Mechanics. In this
work, we present a generalization of Bopp operators for spins and apply our
results to the case of open spin systems. This approach allows to take the
classical limit in a transparent way, recovering the corresponding
Fokker-Planck equation.
| [
{
"version": "v1",
"created": "Mon, 20 Nov 2006 16:16:01 GMT"
},
{
"version": "v2",
"created": "Fri, 20 Apr 2007 13:58:18 GMT"
}
]
| 2008-11-26T00:00:00 | [
[
"Zueco",
"D.",
""
],
[
"Calvo",
"Ivan",
""
]
]
|
quant-ph/0611195 | An Min Wang | Jian Tang and An Min Wang | A case concerning the improved transition probability | 8 pages, 3 figures. This is an example of our serial studies:
quant-ph/0611216, quant-ph/0611217, and quant-ph/0601051 | null | null | null | quant-ph physics.atom-ph | null | As is well known, the existed perturbation theory can be applied to
calculations of energy, state and transition probability in many quantum
systems. However, there are different paths and methods to improve its
calculation precision and efficiency in our view. According to an improved
scheme of perturbation theory proposed by [An Min Wang, quant-ph/0611217], we
reconsider the transition probability and perturbed energy for a Hydrogen atom
in a constant magnetic field. We find the results obtained by using Wang's
scheme are indeed more satisfying in the calculation precision and efficiency.
Therefore, Wang's scheme can be thought of as a powerful tool in the
perturbation calculation of quantum systems.
| [
{
"version": "v1",
"created": "Sat, 18 Nov 2006 10:55:26 GMT"
},
{
"version": "v2",
"created": "Tue, 21 Nov 2006 07:57:56 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Tang",
"Jian",
""
],
[
"Wang",
"An Min",
""
]
]
|
quant-ph/0611196 | Wang Zhiwei | Zhi-Wei Wang, Yun-Feng Huang, Xi-Feng Ren, Yong-Sheng Zhang, and
Guang-Can Guo | Experimental entanglement verification and quantification via
uncertainty relations | 5 pages, 3 figures and 2 tables | Europhysics Letters, 78, 40002 (2007) | 10.1209/0295-5075/78/40002 | null | quant-ph | null | We report on experimental studies on entanglement quantification and
verification based on uncertainty relations for systems consisting of two
qubits. The new proposed measure is shown to be invariant under local unitary
transformations, by which entanglement quantification is implemented for
two-qubit pure states. The nonlocal uncertainty relations for two-qubit pure
states are also used for entanglement verification which serves as a basic
proposition and promise to be a good choice for verification of multipartite
entanglement.
| [
{
"version": "v1",
"created": "Sat, 18 Nov 2006 11:54:26 GMT"
},
{
"version": "v2",
"created": "Wed, 22 Nov 2006 03:42:15 GMT"
},
{
"version": "v3",
"created": "Wed, 4 Apr 2007 08:26:58 GMT"
},
{
"version": "v4",
"created": "Wed, 9 May 2007 13:03:18 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Wang",
"Zhi-Wei",
""
],
[
"Huang",
"Yun-Feng",
""
],
[
"Ren",
"Xi-Feng",
""
],
[
"Zhang",
"Yong-Sheng",
""
],
[
"Guo",
"Guang-Can",
""
]
]
|
quant-ph/0611197 | Hwasung Lee | Hwasung Lee, Y. J. Lee | Determinable Solutions for One-dimensional Quantum Potentials:
Scattering, Quasi-bound and Bound State Problems | 9 pages, 7 figures, Currected typos and clarified the discussion of
double square well | null | 10.1088/1751-8113/40/13/017 | null | quant-ph | null | We derive analytic expressions of the recursive solutions to the
Schr\"{o}dinger's equation by means of a cutoff potential technique for
one-dimensional piecewise constant potentials. These solutions provide a method
for accurately determining the transmission probabilities as well as the wave
function in both classically accessible region and inaccessible region for any
barrier potentials. It is also shown that the energy eigenvalues and the wave
functions of bound states can be obtained for potential-well structures by
exploiting this method. Calculational results of illustrative examples are
shown in order to verify this method for treating barrier and potential-well
problems.
| [
{
"version": "v1",
"created": "Sun, 19 Nov 2006 09:27:15 GMT"
},
{
"version": "v2",
"created": "Sat, 6 Jan 2007 18:00:34 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Lee",
"Hwasung",
""
],
[
"Lee",
"Y. J.",
""
]
]
|
quant-ph/0611198 | Yury Sherkunov | Yury Sherkunov | Casimir interaction between gas media of excited atoms | Bio-dielectrics: Theories, Mechanisms, and Applications. 10-12 April
2006, University of Leicester, UK To be published in Journal of Physics D:
Applied Physics | J.Phys. D: Appl. Phys. 40 (2007) 86-94 | 10.1088/0022-3727/40/1/S13 | null | quant-ph | null | The retarded dispersion interaction (Casimir interaction) between two dilute
dielectric media at high temperatures is considered. The excited atoms are
taken into account. It is shown that the perturbation technique can not be
applied to this problem due to the divergence of integrals. A non-perturbative
approach based on kinetic Green functions is implemented. We consider
interaction between two atoms (one of them is excited0 embedded in an absorbing
dielectric medium. We take into account possible absorption of photons in the
medium, which solves the problem of divergence. The force between two plane
dilute dielectric media is calculated at pair interaction approximation. We
show that the result of quantum electrodynamics differs from the Lifshitz
formula for dilute gas media at high temperatures (if the number of excited
atoms is significant). According to quantum electrodynamics, the interaction
may be either attractive or repulsive depending on the temperature and the
density numbers of the media.
| [
{
"version": "v1",
"created": "Sun, 19 Nov 2006 12:41:31 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Sherkunov",
"Yury",
""
]
]
|
quant-ph/0611199 | Aikaterini Mandilara | A. Mandilara, V. M. Akulin, M. Kolar, G. Kurizki | Control of multiatom entanglement in a cavity | 11 pages, 1 figure. Finalized version | Phys. Rev. A 75, 022327 (2007) | 10.1103/PhysRevA.75.022327 | null | quant-ph | null | We propose a general formalism for analytical description of multiatomic
ensembles interacting with a single mode quantized cavity field under the
assumption that most atoms remain un-excited on average. By combining the
obtained formalism with the nilpotent technique for the description of
multipartite entanglement we are able to overview in a unified fashion
different probabilistic control scenarios of entanglement among atoms or
examine atomic ensembles. We then apply the proposed control schemes to the
creation of multiatom states useful for quantum information.
| [
{
"version": "v1",
"created": "Sun, 19 Nov 2006 15:45:21 GMT"
},
{
"version": "v2",
"created": "Wed, 7 Mar 2007 17:38:26 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Mandilara",
"A.",
""
],
[
"Akulin",
"V. M.",
""
],
[
"Kolar",
"M.",
""
],
[
"Kurizki",
"G.",
""
]
]
|
quant-ph/0611200 | Fernando M. Cucchietti | W.H. Zurek, F.M. Cucchietti, and J.P. Paz | Gaussian Decoherence and Gaussian Echo from Spin Environments | Improved text and figures, to appear in the special issue of Acta
Physica Polonica B celebrating the 100th anniversary of Smoluchowski's
equation and his paper explaining Brownian motion (in
http://th-www.if.uj.edu.pl/acta/vol38/pdf/v38p1685.pdf) | Acta Physica Polonica B, 38, No. 5 (2007), 1685 | null | LA-UR 06-7697 | quant-ph cond-mat.other | null | We examine an exactly solvable model of decoherence -- a spin-system
interacting with a collection of environment spins. We show that in this simple
model (introduced some time ago to illustrate environment--induced
superselection) generic assumptions about the coupling strengths lead to a
universal (Gaussian) suppression of coherence between pointer states. We
explore the regime of validity of this result and discuss its relation to
spectral features of the environment. We also consider its relevance to the
experiments on the so-called Loschmidt echo (which measures, in effect, the
fidelity between the initial and time-reversed or "echo" signal). In
particular, we show that for partial reversals (e.g., when of only a part of
the total Hamiltonian changes sign) fidelity will exhibit a Gaussian dependence
on the time of reversal. In such cases echo may become independent of the
details of the reversal procedure or the specifics of the coupling to the
environment. This puzzling behavior was observed in several NMR experiments.
Natural candidates for such two environments (one of which is easily reversed,
while the other is ``irreversible'') are suggested for the experiment involving
ferrocene.
| [
{
"version": "v1",
"created": "Sun, 19 Nov 2006 18:57:27 GMT"
},
{
"version": "v2",
"created": "Thu, 1 Feb 2007 17:39:15 GMT"
},
{
"version": "v3",
"created": "Mon, 26 Mar 2007 16:54:15 GMT"
}
]
| 2007-05-25T00:00:00 | [
[
"Zurek",
"W. H.",
""
],
[
"Cucchietti",
"F. M.",
""
],
[
"Paz",
"J. P.",
""
]
]
|
quant-ph/0611201 | Tam\'as V\'ertesi | T. V\'ertesi | Power of unentangled measurements on two antiparallel spins | Latex file, 18 pages, 1 figure; published version | Phys. Rev. A 75, 032343 (2007) | 10.1103/PhysRevA.75.032343 | null | quant-ph | null | We consider a pair of antiparallel spins polarized in a random direction to
encode quantum information. We wish to extract as much information as possible
on the polarization direction attainable by an unentangled measurement, i.e.,
by a measurement, whose outcomes are associated with product states. We develop
analytically the upper bound 0.7935 bits to the Shannon mutual information
obtainable by an unentangled measurement, which is definitely less than the
value 0.8664 bits attained by an entangled measurement. This proves our main
result, that not every ensemble of product states can be optimally
distinguished by an unentangled measurement, if the measure of
distinguishability is defined in the sense of Shannon. We also present results
from numerical calculations and discuss briefly the case of parallel spins.
| [
{
"version": "v1",
"created": "Sun, 19 Nov 2006 21:01:55 GMT"
},
{
"version": "v2",
"created": "Mon, 16 Apr 2007 07:18:27 GMT"
}
]
| 2013-05-29T00:00:00 | [
[
"Vértesi",
"T.",
""
]
]
|
quant-ph/0611202 | James P. Crutchfield | James P. Crutchfield and Karoline Wiesner | Intrinsic Quantum Computation | 5 pages, 1 figure, 1 table; updated with corrections;
http://cse.ucdavis.edu/~cmg/compmech/pubs/iqc.htm | null | 10.1016/j.physleta.2007.07.052 | Santa Fe Institute Working Paper 06-11-045 | quant-ph | null | We introduce ways to measure information storage in quantum systems, using a
recently introduced computation-theoretic model that accounts for measurement
effects. The first, the quantum excess entropy, quantifies the shared
information between a quantum process's past and its future. The second, the
quantum transient information, determines the difficulty with which an observer
comes to know the internal state of a quantum process through measurements. We
contrast these with von Neumann entropy and quantum entropy rate and provide a
closed-form expression for the latter for the class of deterministic quantum
processes.
| [
{
"version": "v1",
"created": "Sun, 19 Nov 2006 20:16:44 GMT"
},
{
"version": "v2",
"created": "Fri, 16 Feb 2007 00:48:47 GMT"
}
]
| 2010-04-05T00:00:00 | [
[
"Crutchfield",
"James P.",
""
],
[
"Wiesner",
"Karoline",
""
]
]
|
quant-ph/0611203 | James P. Crutchfield | Karoline Wiesner and James P. Crutchfield | Language Diversity of Measured Quantum Processes | 9 pages, 4 tables;
http://cse.ucdavis.edu/~cmg/compmech/pubs/ldmqp.htm | null | null | null | quant-ph | null | The behavior of a quantum system depends on how it is measured. How much of
what is observed comes from the structure of the quantum system itself and how
much from the observer's choice of measurement? We explore these questions by
analyzing the \emph{language diversity} of quantum finite-state generators. One
result is a new way to distinguish quantum devices from their classical
(stochastic) counterparts. While the diversity of languages generated by these
two computational classes is the same in the case of periodic processes,
quantum systems generally generate a wider range of languages than classical
systems.
| [
{
"version": "v1",
"created": "Sun, 19 Nov 2006 20:54:20 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Wiesner",
"Karoline",
""
],
[
"Crutchfield",
"James P.",
""
]
]
|
quant-ph/0611204 | Gabriel Hetet | G. H\'etet, O. Gl\"ockl, K. A. Pilypas, C.C. Harb, B.C. Buchler, H.-A.
Bachor, P.K. Lam | Squeezed light for bandwidth limited atom optics experiments at the
Rubidium D1 line | 8 pages, 3 figures. Accepted for Journal of Physics B | null | 10.1088/0953-4075/40/1/020 | null | quant-ph | null | We report on the generation of more than 5 dB of vacuum squeezed light at the
Rubidium D1 line (795 nm) using periodically poled KTiOPO$_{4}$ (PPKTP) in an
optical parametric oscillator. We demonstrate squeezing at low sideband
frequencies, making this source of non-classical light compatible with
bandwidth limited atom optics experiments. When PPKTP is operated as a
parametric amplifier, we show a noise reduction of 4 dB stably locked within
the 150 kHz-500 kHz frequency range. This matches the bandwidth of
Electromagnetically Induced Transparency (EIT) in Rubidium hot vapour cells
under the condition of large information delay.
| [
{
"version": "v1",
"created": "Mon, 20 Nov 2006 02:57:13 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Hétet",
"G.",
""
],
[
"Glöckl",
"O.",
""
],
[
"Pilypas",
"K. A.",
""
],
[
"Harb",
"C. C.",
""
],
[
"Buchler",
"B. C.",
""
],
[
"Bachor",
"H. -A.",
""
],
[
"Lam",
"P. K.",
""
]
]
|
quant-ph/0611205 | Rui Guo | Rui Guo and Hong Guo | Momentum entanglement and disentanglement between atom and photon | 6 pages, 10 figures | null | 10.1103/PhysRevA.76.012112 | null | quant-ph | null | With the quantum interference between two transition pathways, we demonstrate
a novel scheme to coherently control the momentum entanglement between a single
atom and a single photon. The unavoidable disentanglement is also studied from
the first principle, which indicates that the stably entangled atom--photon
system with superhigh degree of entanglement may be realized with this scheme
under certain conditions.
| [
{
"version": "v1",
"created": "Mon, 20 Nov 2006 05:08:39 GMT"
},
{
"version": "v2",
"created": "Wed, 28 Feb 2007 04:28:34 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Guo",
"Rui",
""
],
[
"Guo",
"Hong",
""
]
]
|
quant-ph/0611206 | Qin Guo | Hong-yi Fan, Qin Guo | Husimi operator and Husimi function for describing electron's
probability distribution in uniform magnetic field derived by virtue of the
entangled state representation | 15pages | null | null | null | quant-ph | null | For the first time we introduce the Husimi operator
Delta_h(gamma,varepsilon;kappa) for studying Husimi distribution in phase
space(gamma,varepsilon) for electron's states in uniform magnetic field, where
kappa is the Gaussian spatial width parameter. Using the Wigner operator in the
entangled state |lambda> representation [Hong-Yi Fan, Phys. Lett. A 301
(2002)153; A 126 (1987) 145) we find that Delta_h(gamma,varepsilon;kappa) is
just a pure squeezed coherent state density operator |gamma,varepsilon>_kappa
kappa<gamma,varepsilon|, which brings convenience for studying and calculating
the Husimi distribution. We in many ways demonstrate that the Husimi
distributions are Gaussian-broadened version of the Wigner distributions.
Throughout our calculation we have fully employed the technique of integration
within an ordered product of operators.
| [
{
"version": "v1",
"created": "Mon, 20 Nov 2006 09:37:18 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Fan",
"Hong-yi",
""
],
[
"Guo",
"Qin",
""
]
]
|
quant-ph/0611207 | Ba An Nguyen | Nguyen Ba An | Reply to Yang et al.'s comment | 1 page, No figures, RevTex | null | null | null | quant-ph | null | This is to reply to a recent comment by Yang, Yuan and Zhang on
``Teleportation of two-quNit entanglement: Exploiting local resorces''.
| [
{
"version": "v1",
"created": "Mon, 20 Nov 2006 14:19:05 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"An",
"Nguyen Ba",
""
]
]
|
quant-ph/0611208 | Heinz-Peter Breuer | Heinz-Peter Breuer | Non-Markovian generalization of the Lindblad theory of open quantum
systems | 10 pages, 1 figure, replaced by published version | Phys. Rev. A 75, 022103 (2007) | 10.1103/PhysRevA.75.022103 | null | quant-ph | null | A systematic approach to the non-Markovian quantum dynamics of open systems
is given by the projection operator techniques of nonequilibrium statistical
mechanics. Combining these methods with concepts from quantum information
theory and from the theory of positive maps, we derive a class of correlated
projection superoperators that take into account in an efficient way
statistical correlations between the open system and its environment. The
result is used to develop a generalization of the Lindblad theory to the regime
of highly non-Markovian quantum processes in structured environments.
| [
{
"version": "v1",
"created": "Mon, 20 Nov 2006 15:04:26 GMT"
},
{
"version": "v2",
"created": "Sat, 17 Feb 2007 15:38:10 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Breuer",
"Heinz-Peter",
""
]
]
|
quant-ph/0611209 | Iordanis Kerenidis | Dmytro Gavinsky, Julia Kempe, Iordanis Kerenidis, Ran Raz, Ronald de
Wolf | Exponential separations for one-way quantum communication complexity,
with applications to cryptography | 16 pages, improved version, supersedes quant-ph/0607173 and
quant-ph/0607174 although some proofs are different | Proc. 39th STOC, p. 516-525 (2007) | null | null | quant-ph | null | We give an exponential separation between one-way quantum and classical
communication protocols for a partial Boolean function (a variant of the
Boolean Hidden Matching Problem of Bar-Yossef et al.) Earlier such an
exponential separation was known only for a relational problem. The
communication problem corresponds to a \emph{strong extractor} that fails
against a small amount of \emph{quantum} information about its random source.
Our proof uses the Fourier coefficients inequality of Kahn, Kalai, and Linial.
We also give a number of applications of this separation. In particular, we
show that there are privacy amplification schemes that are secure against
classical adversaries but not against quantum adversaries; and we give the
first example of a key-expansion scheme in the model of bounded-storage
cryptography that is secure against classical memory-bounded adversaries but
not against quantum ones.
| [
{
"version": "v1",
"created": "Mon, 20 Nov 2006 17:35:42 GMT"
},
{
"version": "v2",
"created": "Mon, 26 Mar 2007 11:09:26 GMT"
},
{
"version": "v3",
"created": "Wed, 13 Feb 2008 10:45:18 GMT"
}
]
| 2022-03-29T00:00:00 | [
[
"Gavinsky",
"Dmytro",
""
],
[
"Kempe",
"Julia",
""
],
[
"Kerenidis",
"Iordanis",
""
],
[
"Raz",
"Ran",
""
],
[
"de Wolf",
"Ronald",
""
]
]
|
quant-ph/0611210 | Alexander L\'opez | Alexander L\'opez, Otto Rend\'on, V\'ictor M. Villalba, Ernesto Medina | Two electron entanglement in quasi-one dimensional system: Role of
resonances | 4 pages, 3 figures | null | 10.1103/PhysRevB.75.033401 | null | quant-ph | null | We analyze the role of resonances in two-fermion entanglement production for
a quasi one-dimensional two channel scattering problem. We solve exactly for
the problem of a two-fermion antisymmetric product state scattering off a
double delta well potential. It is shown that the two-particle concurrence of
the post-selected state has an oscillatory behavior where the concurrence
vanishes at the values of momenta for virtual bound states in the double well.
These concurrence zeros are interpreted in terms of the uncertainty in the
knowledge of the state of the one particle subspace reduced one particle
density matrix. Our results suggest manipulation of fermion entanglement
production through the resonance structure of quantum dots.
| [
{
"version": "v1",
"created": "Mon, 20 Nov 2006 20:43:53 GMT"
}
]
| 2016-08-16T00:00:00 | [
[
"López",
"Alexander",
""
],
[
"Rendón",
"Otto",
""
],
[
"Villalba",
"Víctor M.",
""
],
[
"Medina",
"Ernesto",
""
]
]
|
quant-ph/0611211 | Philip Pearle | Philip Pearle | How Stands Collapse I | 20 pages, to be published in Journal of Physics A: Math-Gen | null | null | null | quant-ph | null | In this volume in honor of GianCarlo Ghirardi, I discuss my involvement with
ideas of dynamical collapse of the state vector. 10 problems are introduced, 9
of which were seen following my initial work. 4 of these problems had a
resolution in GianCarlo Ghirardi, Alberto Rimini and Tullio Weber's Spontaneous
Localization (SL) model (which added 1 more problem). This stimulated a
(somewhat different) resolution of these 5 problems in the Continuous
Spontaneous Localization (CSL) model, in which I combined my initial work with
SL. In an upcoming volume in honor of Abner Shimony I shall discuss the status
of the 5 remaining post-CSL problems.
| [
{
"version": "v1",
"created": "Mon, 20 Nov 2006 20:52:36 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Pearle",
"Philip",
""
]
]
|
quant-ph/0611212 | Philip Pearle | Philip Pearle | How Stands Collapse II | 37 pages | null | 10.1088/1751-8113/40/12/S18 | null | quant-ph | null | I review ten problems associated with the dynamical wave function collapse
program, which were described in the first of these two papers. Five of these,
the \textit{interaction, preferred basis, trigger, symmetry} and
\textit{superluminal} problems, were discussed as resolved there. In this
volume in honor of Abner Shimony, I discuss the five remaining problems,
\textit{tails, conservation law, experimental, relativity, legitimization}.
Particular emphasis is given to the tails problem, first raised by Abner. The
discussion of legitimization contains a new argument, that the energy density
of the fluctuating field which causes collapse should exert a gravitational
force. This force can be repulsive, since this energy density can be negative.
Speculative illustrations of cosmological implications are offered.
| [
{
"version": "v1",
"created": "Mon, 20 Nov 2006 21:01:06 GMT"
},
{
"version": "v2",
"created": "Wed, 30 May 2007 18:48:47 GMT"
},
{
"version": "v3",
"created": "Mon, 29 Oct 2007 19:30:38 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Pearle",
"Philip",
""
]
]
|
quant-ph/0611213 | Alina Dubrovska | Alina Dubrovska Vasilieva, Taisia Mischenko-Slatenkova | Quantum Query Algorithms for Certain Problems and Generalization of
Algorithm Designing Techniques | 23 pages, 7 figures | null | null | null | quant-ph | null | Quantum algorithms can be analyzed in a query model to compute Boolean
functions where input is given in a black box, but the aim is to compute
function value for arbitrary input using as few queries as possible. In this
paper we concentrate on quantum query algorithm designing tasks. The main aim
of research was to find new efficient algorithms and develop general algorithm
designing techniques. We present several exact quantum query algorithms for
certain problems that are better than classical counterparts. Next we introduce
algorithm transformation methods that allow significant enlarging of sets of
exactly computable functions. Finally, we propose algorithm constructing
methods applicable for algorithms with specific properties that allow
constructing algorithms for more complex functions preserving acceptable error
probability and number of queries.
| [
{
"version": "v1",
"created": "Tue, 21 Nov 2006 13:47:59 GMT"
}
]
| 2012-03-24T00:00:00 | [
[
"Vasilieva",
"Alina Dubrovska",
""
],
[
"Mischenko-Slatenkova",
"Taisia",
""
]
]
|
quant-ph/0611214 | Bei Zeng | Bei Zeng, Hyeyoun Chung, Andrew W. Cross, Isaac L. Chuang | Local unitary versus local Clifford equivalence of stabilizer and graph
states | Revised version according to referee's comments. To appear in
Physical Review A | null | 10.1103/PhysRevA.75.032325 | null | quant-ph | null | The equivalence of stabilizer states under local transformations is of
fundamental interest in understanding properties and uses of entanglement. Two
stabilizer states are equivalent under the usual stochastic local operations
and classical communication criterion if and only if they are equivalent under
local unitary (LU) operations. More surprisingly, under certain conditions, two
LU equivalent stabilizer states are also equivalent under local Clifford (LC)
operations, as was shown by Van den Nest et al. [Phys. Rev. \textbf{A71},
062323]. Here, we broaden the class of stabilizer states for which LU
equivalence implies LC equivalence ($LU\Leftrightarrow LC$) to include all
stabilizer states represented by graphs with neither cycles of length 3 nor 4.
To compare our result with Van den Nest et al.'s, we show that any stabilizer
state of distance $\delta=2$ is beyond their criterion. We then further prove
that $LU\Leftrightarrow LC$ holds for a more general class of stabilizer states
of $\delta=2$. We also explicitly construct graphs representing $\delta>2$
stabilizer states which are beyond their criterion: we identify all 58 graphs
with up to 11 vertices and construct graphs with $2^m-1$ ($m\geq 4$) vertices
using quantum error correcting codes which have non-Clifford transversal gates.
| [
{
"version": "v1",
"created": "Tue, 21 Nov 2006 15:31:14 GMT"
},
{
"version": "v2",
"created": "Fri, 16 Mar 2007 21:54:27 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Zeng",
"Bei",
""
],
[
"Chung",
"Hyeyoun",
""
],
[
"Cross",
"Andrew W.",
""
],
[
"Chuang",
"Isaac L.",
""
]
]
|
quant-ph/0611215 | Rong Wu | Rong Wu, Alexander Pechen, Constantin Brif and Herschel Rabitz | Controllability of open quantum systems with Kraus-map dynamics | 16 pages | J. Phys. A: Math. Theor. 40, 5681 (2007) | 10.1088/1751-8113/40/21/015 | null | quant-ph math-ph math.MP | null | This paper presents a constructive proof of complete kinematic state
controllability of finite-dimensional open quantum systems whose dynamics are
represented by Kraus maps. For any pair of states (pure or mixed) on the
Hilbert space of the system, we explicitly show how to construct a Kraus map
that transforms one state into another. Moreover, we prove by construction the
existence of a Kraus map that transforms all initial states into a predefined
target state (such a process may be used, for example, in quantum information
dilution). Thus, in sharp contrast to unitary control, Kraus-map dynamics
allows for the design of controls which are robust to variations in the initial
state of the system. The general formalism is illustrated with examples of
state-to-state Kraus transformations in a two-level system. In particular, we
construct a family of non-unitary Kraus maps, which transform one pure state
into another. The problem of dynamic state controllability of open quantum
systems (i.e., controllability of state-to-state transformations, given a set
of available dynamical resources such as coherent controls, incoherent
interactions with the environment, and measurements) is also discussed.
| [
{
"version": "v1",
"created": "Tue, 21 Nov 2006 15:44:41 GMT"
},
{
"version": "v2",
"created": "Sun, 27 May 2007 23:22:12 GMT"
}
]
| 2008-01-22T00:00:00 | [
[
"Wu",
"Rong",
""
],
[
"Pechen",
"Alexander",
""
],
[
"Brif",
"Constantin",
""
],
[
"Rabitz",
"Herschel",
""
]
]
|
quant-ph/0611216 | An Min Wang | An Min Wang | Quantum mechanics in general quantum systems (I): Exact solution | 21 pages, no figure. The first paper in our serial studies. Its
earlier version is quant-ph/0602055 | null | null | null | quant-ph math-ph math.MP | null | Starting from our idea of combining the Feynman path integral spirit and the
Dyson series kernel, we find an explicit and general form of time evolution
operator that is a $c$-number function and a power series of perturbation
including all order approximations in the unperturbed Hamiltonian
representation. Based on it, we obtain an exact solution of the Schr\"{o}dinger
equation in general quantum systems independent of time. Comparison of our
exact solution with the existed perturbation theory makes some features and
significance of our exact solution clear. The conclusions expressly indicate
that our exact solution is obviously consistent with the usual time-independent
perturbation theory at any order approximation, it explicitly calculates out
the expanding coefficients of the unperturbed state in the non-perturbation
method, and it fully solves the recurrence equation of the expansion
coefficients of final state in the unperturbed Hamiltonian representation from
a view of time-dependent perturbation theory. At the same time, the exact
solution of the von Neumann equation is also given. Our results can be thought
of as theoretical developments of quantum dynamics, and are helpful for
understanding the dynamical behavior and related subjects of general quantum
systems in both theory and application. Our exact solution, together with its
sequence studies on perturbation theory [An Min Wang, quant-ph/0611217] and
open system dynamics [An Min Wang, quant-ph/0601051] can be used to establish
the foundation of theoretical formulism of quantum mechanics in general quantum
systems. Further applications of our exact solution to quantum theory can be
expected.
| [
{
"version": "v1",
"created": "Tue, 21 Nov 2006 16:58:24 GMT"
},
{
"version": "v2",
"created": "Wed, 22 Nov 2006 02:32:39 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Wang",
"An Min",
""
]
]
|
quant-ph/0611217 | An Min Wang | An Min Wang | Quantum mechanics in general quantum systems (II): Perturbation theory | 51 pages, no figure. The second paper in our serial studies. Its
earlier version is quant-ph/0602055 | null | null | null | quant-ph math-ph math.MP physics.atom-ph | null | We propose an improved scheme of perturbation theory based on our exact
solution [An Min Wang, quant-ph/0611216] in general quantum systems independent
of time. Our elementary start-point is to introduce the perturbing parameter as
late as possible. Our main skills are Hamiltonian redivision so as to overcome
a flaw of the usual perturbation theory, and the perturbing Hamiltonian matrix
product decomposition in order to separate the contraction and anti-contraction
terms. Our calculational technology is the limit process for eliminating
apparent divergences. Our central idea is ``dynamical rearrangement and
summation" for the sake of the partial contributions from the high order even
all order approximations absorbed in our perturbed solution. Consequently, we
obtain the improved forms of the zeroth, first, second and third order
perturbed solutions absorbing the partial contributions from the high order
even all order approximations of perturbation. Then we deduce the improved
transition probability. In special, we propose the revised Fermi's golden rule.
Moreover, we apply our scheme to obtain the improved forms of perturbed energy
and perturbed state. In addition, we study an easy understanding example of
two-state system to illustrate our scheme and show its advantages. All of this
implies the physical reasons and evidences why our improved scheme of
perturbation theory are actually calculable, operationally efficient,
conclusively more accurate. Our improved scheme is the further development and
interesting application of our exact solution, and it has been successfully
used to study on open system dynamics [An Min Wang, quant-ph/0601051].
| [
{
"version": "v1",
"created": "Tue, 21 Nov 2006 16:58:46 GMT"
},
{
"version": "v2",
"created": "Wed, 22 Nov 2006 02:47:15 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Wang",
"An Min",
""
]
]
|
quant-ph/0611218 | Georgios Roumpos | Georgios Roumpos, Cyrus P. Master and Yoshihisa Yamamoto | Quantum simulation of spin ordering with nuclear spins in a solid state
lattice | 11 pages, 3 figues; Published version | Phys. Rev. B 75, 094415 (2007) | 10.1103/PhysRevB.75.094415 | null | quant-ph cond-mat.stat-mech | null | An experiment demonstrating the quantum simulation of a spin-lattice
Hamiltonian is proposed. Dipolar interactions between nuclear spins in a solid
state lattice can be modulated by rapid radio-frequency pulses. In this way,
the effective Hamiltonian of the system can be brought to the form of an
antiferromagnetic Heisenberg model with long range interactions. Using a
semiconducting material with strong optical properties such as InP, cooling of
nuclear spins could be achieved by means of optical pumping. An additional
cooling stage is provided by adiabatic demagnetization in the rotating frame
(ADRF) down to a nuclear spin temperature at which we expect a phase transition
from a paramagnetic to antiferromagnetic phase. This phase transition could be
observed by probing the magnetic susceptibility of the spin-lattice. Our
calculations suggest that employing current optical pumping technology,
observation of this phase transition is within experimental reach.
| [
{
"version": "v1",
"created": "Tue, 21 Nov 2006 18:03:13 GMT"
},
{
"version": "v2",
"created": "Tue, 20 Mar 2007 17:42:59 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Roumpos",
"Georgios",
""
],
[
"Master",
"Cyrus P.",
""
],
[
"Yamamoto",
"Yoshihisa",
""
]
]
|
quant-ph/0611219 | Steven J. van Enk | S.J. van Enk, N. Lutkenhaus, and H.J. Kimble | On experimental procedures for entanglement verification | 15 pages | Phys. Rev. A 75, 052318 (2007) | 10.1103/PhysRevA.75.052318 | null | quant-ph cond-mat.other | null | We give an overview of different types of entanglement that can be generated
in experiments, as well as of various protocols that can be used to verify or
quantify entanglement. We propose several criteria that, we argue, should be
applied to experimental entanglement verification procedures. Explicit examples
demonstrate that not following these criteria will tend to result in
overestimating the amount of entanglement generated in an experiment or in
infering entanglement when there is none. We distinguish protocols meant to
refute or eliminate hidden-variable models from those meant to verify
entanglement.
| [
{
"version": "v1",
"created": "Tue, 21 Nov 2006 18:28:01 GMT"
},
{
"version": "v2",
"created": "Wed, 28 Mar 2007 17:13:25 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"van Enk",
"S. J.",
""
],
[
"Lutkenhaus",
"N.",
""
],
[
"Kimble",
"H. J.",
""
]
]
|
quant-ph/0611220 | Fedor Herbut | Fedor Herbut | Complete "Born's rule" from "environment-assisted invariance" in terms
of pure-state twin unitaries | 25 pages, Latex2e and Revtex4 | Journal of Physics A: Math. and Theor. 40, 5949 (2007) | 10.1088/1751-8113/40/22/013 | null | quant-ph | null | Zurek's derivation of the Born rule from envariance (environment-assisted
invariance) is tightened up, somewhat generalized, and extended to encompass
all possibilities. By this, besides Zurek's most important work, also the works
of 5 other commentators of the derivation are taken into account, and selected
excerpts commented upon. All this is done after a detailed theory of twin
unitaries, which are the other face of envariance.
| [
{
"version": "v1",
"created": "Tue, 21 Nov 2006 20:00:53 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Herbut",
"Fedor",
""
]
]
|
quant-ph/0611221 | Carl Maes | C. Maes, J. Asboth, H. Ritsch | Self ordering and superradiant backscattering of a gaseous beam in a
ring cavity with counter propagating pump | 18 pages 11 figures | null | 10.1364/OE.15.006019 | null | quant-ph | null | We study the threshold conditions of spatial self organization combined with
collective coherent optical backscattering of a thermal gaseous beam moving in
a high Q ring cavity with counter propagating pump. We restrict ourselves to
the limit of large detuning between the particles optical resonances and the
light field, where spontaneous emission is negligible and the particles can be
treated as polarizable point masses. Using a linear stability analysis in the
accelerated rest frame of the particles we derive an analytic bounds for the
selforganization as a function of particle number,average velocity, temperature
and resonator parameters. We check our results by a numerical iteration
procedure as well as by direct simulations of the N-particle dynamics. Due to
momentum conservation the backscattered intensity determines the average force
on the cloud, which gives the conditions for stopping and cooling a fast
molecular beam.
| [
{
"version": "v1",
"created": "Tue, 21 Nov 2006 22:26:45 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Maes",
"C.",
""
],
[
"Asboth",
"J.",
""
],
[
"Ritsch",
"H.",
""
]
]
|
quant-ph/0611222 | Adrian Budini | Adrian A. Budini | Lindblad rate equations | 12 pages, 2 figures | Phys. Rev. A 74, 053815 (2006) | 10.1103/PhysRevA.74.053815 | null | quant-ph | null | In this paper we derive an extra class of non-Markovian master equations
where the system state is written as a sum of auxiliary matrixes whose
evolution involve Lindblad contributions with local coupling between all of
them, resembling the structure of a classical rate equation. The system
dynamics may develops strong non-local effects such as the dependence of the
stationary properties with the system initialization. These equations are
derived from alternative microscopic interactions, such as complex environments
described in a generalized Born-Markov approximation and tripartite
system-environment interactions, where extra unobserved degrees of freedom
mediates the entanglement between the system and a Markovian reservoir.
Conditions that guarantees the completely positive condition of the solution
map are found. Quantum stochastic processes that recover the system dynamics in
average are formulated. We exemplify our results by analyzing the dynamical
action of non-trivial structured dephasing and depolarizing reservoirs over a
single qubit.
| [
{
"version": "v1",
"created": "Tue, 21 Nov 2006 23:53:40 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Budini",
"Adrian A.",
""
]
]
|
quant-ph/0611223 | Fabrizio Buscemi | Fabrizio Buscemi, Paolo Bordone and Andrea Bertoni | Linear entropy as an entanglement measure in two-fermion systems | 16 pages. Added references in section 1 Corrected typos | Phys. Rev. A 75, 032301 (2007) | 10.1103/PhysRevA.75.032301 | null | quant-ph | null | We describe an efficient theoretical criterion, suitable for
indistinguishable particles to quantify the quantum correlations of any pure
two-fermion state, based on the Slater rank concept. It represents the natural
generalization of the linear entropy used to treat quantum entanglement in
systems of non-identical particles. Such a criterion is here applied to an
electron-electron scattering in a two-dimensional system in order to perform a
quantitative evaluation of the entanglement dynamics for various spin
configurations and to compare the linear entropy with alternative approaches.
Our numerical results show the dependence of the entanglement evolution upon
the initial state of the system and its spin components. The differences with
previous analyses accomplished by using the von Neumann entropy are discussed.
The evaluation of the entanglement dynamics in terms of the linear entropy
results to be much less demanding from the computational point of view, not
requiring the diagonalization of the density matrix.
| [
{
"version": "v1",
"created": "Wed, 22 Nov 2006 07:47:48 GMT"
},
{
"version": "v2",
"created": "Fri, 2 Mar 2007 07:51:08 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Buscemi",
"Fabrizio",
""
],
[
"Bordone",
"Paolo",
""
],
[
"Bertoni",
"Andrea",
""
]
]
|
quant-ph/0611224 | Jian-Ming Cai | Jian-Ming Cai, Zheng-Wei Zhou, Shun Zhang and Guang-Can Guo | Compatibility conditions from multipartite entanglement measures | 5 pages | Phys. Rev. A 75, 052324 (2007) | 10.1103/PhysRevA.75.052324 | null | quant-ph | null | We consider an arbitrary d_{1}\otimes d_{2}\otimes ... \otimes d_{N}
composite quantum system and find necessary conditions for general m-party
subsystem states to be the reduced states of a common N-party state. These
conditions will lead to various monogamy inequalities for bipartite quantum
entanglement and partial disorder in multipartite states. Our results are
tightly connected with the measures of multipartite entanglement.
| [
{
"version": "v1",
"created": "Wed, 22 Nov 2006 09:09:05 GMT"
},
{
"version": "v2",
"created": "Fri, 24 Nov 2006 07:02:49 GMT"
},
{
"version": "v3",
"created": "Sat, 25 Nov 2006 02:24:59 GMT"
},
{
"version": "v4",
"created": "Thu, 21 Dec 2006 07:50:02 GMT"
},
{
"version": "v5",
"created": "Sat, 30 Dec 2006 01:01:56 GMT"
},
{
"version": "v6",
"created": "Mon, 4 Jun 2007 12:33:49 GMT"
}
]
| 2007-06-13T00:00:00 | [
[
"Cai",
"Jian-Ming",
""
],
[
"Zhou",
"Zheng-Wei",
""
],
[
"Zhang",
"Shun",
""
],
[
"Guo",
"Guang-Can",
""
]
]
|
quant-ph/0611225 | Gong Zhe-Xuan | Wen-Xing Yang and Zhe-Xuan Gong, et al | Simple scheme for implementing the Deutsch-Jozsa algorithm in thermal
cavity | 7 pages, 4 figures | J. Phys. A: Math. Theor. 40 (2007) 155-161 | 10.1088/1751-8113/40/1/009 | null | quant-ph | null | We present a simple scheme to implement the Deutsch-Jozsa algorithm based on
two-atom interaction in a thermal cavity. The photon-number-dependent parts in
the evolution operator are canceled with the strong resonant classical field
added. As a result, our scheme is immune to thermal field, and does not require
the cavity to remain in the vacuum state throughout the procedure. Besides,
large detuning between the atoms and the cavity is not necessary neither,
leading to potential speed up of quantum operation. Finally, we show by
numerical simulation that the proposed scheme is equal to demonstrate the
Deutsch-Jozsa algorithm with high fidelity.
| [
{
"version": "v1",
"created": "Wed, 22 Nov 2006 09:26:12 GMT"
},
{
"version": "v2",
"created": "Wed, 6 Dec 2006 16:55:27 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Yang",
"Wen-Xing",
""
],
[
"Gong",
"Zhe-Xuan",
""
]
]
|
quant-ph/0611226 | Marko Znidaric | Marko Znidaric | Entanglement of random vectors | 8 pages | J. Phys. A: Math. Theor. 40, F105-F111 (2007) | 10.1088/1751-8113/40/3/F04 | null | quant-ph cond-mat.stat-mech nlin.CD | null | We analytically calculate the average value of i-th largest Schmidt
coefficient for random pure quantum states. Schmidt coefficients, i.e.,
eigenvalues of the reduced density matrix, are expressed in the limit of large
Hilbert space size and for arbitrary bipartite splitting as an implicit
function of index i.
| [
{
"version": "v1",
"created": "Wed, 22 Nov 2006 10:26:00 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Znidaric",
"Marko",
""
]
]
|
quant-ph/0611227 | Claudio Garola | Claudio Garola | Physical propositions and quantum languages | 15 pages, no figure, standard LateX | International Journal of Theoretical Physics (2008), 47: 90-103 | 10.1007/s10773-007-9372-8 | null | quant-ph | null | The word \textit{proposition} is used in physics with different meanings,
which must be distinguished to avoid interpretational problems. We construct
two languages $\mathcal{L}^{\ast}(x)$ and $\mathcal{L}(x)$ with classical
set-theoretical semantics which allow us to illustrate those meanings and to
show that the non-Boolean lattice of propositions of quantum logic (QL) can be
obtained by selecting a subset of \textit{p-testable} propositions within the
Boolean lattice of all propositions associated with sentences of
$\mathcal{L}(x)$. Yet, the aforesaid semantics is incompatible with the
standard interpretation of quantum mechanics (QM) because of known no-go
theorems. But if one accepts our criticism of these theorems and the ensuing SR
(semantic realism) interpretation of QM, the incompatibility disappears, and
the classical and quantum notions of truth can coexist, since they refer to
different metalinguistic concepts (\textit{truth} and \textit{verifiability
according to QM}, respectively). Moreover one can construct a quantum language
$\mathcal{L}_{TQ}(x)$ whose Lindenbaum-Tarski algebra is isomorphic to QL, the
sentences of which state (testable) properties of individual samples of
physical systems, while standard QL does not bear this interpretation.
| [
{
"version": "v1",
"created": "Wed, 22 Nov 2006 11:58:43 GMT"
}
]
| 2014-11-13T00:00:00 | [
[
"Garola",
"Claudio",
""
]
]
|
quant-ph/0611228 | Oxana Mishina Sergeevna | O.S. Mishina, D.V. Kupriyanov, J.H. Muller, E.S. Polzik | Spectral theory of quantum memory and entanglement via Raman scattering
of light by an atomic ensemble | 15 pages, 7 figures; added references; accepted to PRA | Phys. Rev. A 75, 042326 (2007) | 10.1103/PhysRevA.75.042326 | null | quant-ph | null | We discuss theoretically quantum interface between light and a spin polarized
ensemble of atoms with the spin >= 1 based on an off-resonant Raman scattering.
We present the spectral theory of the light-atoms interaction and show how
particular spectral modes of quantum light couple to spatial modes of the
extended atomic ensemble. We show how this interaction can be used for quantum
memory storage and retrieval and for deterministic entanglement protocols. The
proposed protocols are attractive due to their simplicity since they involve
just a single pass of light through atoms without the need for elaborate pulse
shaping or quantum feedback. As a practically relevant example we consider the
interaction of a light pulse with hyperfine components of D1 line of 87Rb. The
quality of the proposed protocols is verified via analytical and numerical
analysis.
| [
{
"version": "v1",
"created": "Wed, 22 Nov 2006 12:14:44 GMT"
},
{
"version": "v2",
"created": "Tue, 27 Feb 2007 13:47:35 GMT"
}
]
| 2010-06-29T00:00:00 | [
[
"Mishina",
"O. S.",
""
],
[
"Kupriyanov",
"D. V.",
""
],
[
"Muller",
"J. H.",
""
],
[
"Polzik",
"E. S.",
""
]
]
|
quant-ph/0611229 | Julio de Vicente | Julio I. de Vicente | Lower bounds on concurrence and separability conditions | 5 pages, 1 figure; minor changes, references added; final version:
minor correction in proof of lemma 1, scope of theorem 2 clarified, to appear
in PRA; mistake in proof of lemma 1 of published version corrected, results
unchanged | Phys. Rev. A 75, 052320 (2007); 77, 039903(E) (2008) | 10.1103/PhysRevA.75.052320 | null | quant-ph | null | We obtain analytical lower bounds on the concurrence of bipartite quantum
systems in arbitrary dimensions related to the violation of separability
conditions based on local uncertainty relations and on the Bloch representation
of density matrices. We also illustrate how these results complement and
improve those recently derived [K. Chen, S. Albeverio, and S.-M. Fei, Phys.
Rev. Lett. 95, 040504 (2005)] by considering the Peres-Horodecki and the
computable cross norm or realignment criteria.
| [
{
"version": "v1",
"created": "Wed, 22 Nov 2006 15:42:45 GMT"
},
{
"version": "v2",
"created": "Tue, 28 Nov 2006 20:34:20 GMT"
},
{
"version": "v3",
"created": "Thu, 26 Apr 2007 10:55:33 GMT"
},
{
"version": "v4",
"created": "Wed, 13 Feb 2008 19:32:12 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"de Vicente",
"Julio I.",
""
]
]
|
quant-ph/0611230 | N. L. Harshman | N.L. Harshman and S. Wickramsekara | Tensor Product Structures, Entanglement, and Particle Scattering | 7 pages, no figures; v.2 typo in references corrected, submitted to
OSID as part of SMP38 | Open Syst.Info.Dyn.14:341-351,2007 | 10.1007/s11080-007-9057-z | null | quant-ph | null | Particle systems admit a variety of tensor product structures (TPSs)
depending on the complete system of commuting observables chosen for the
analysis. Different notions of entanglement are associated with these different
TPSs. Global symmetry transformations and dynamical transformations factor into
products of local unitary operators with respect to certain TPSs and not with
respect to others. Symmetry-invariant and dynamical-invariant TPSs and
corresponding measures of entanglement are defined for particle scattering
systems.
| [
{
"version": "v1",
"created": "Wed, 22 Nov 2006 16:22:51 GMT"
},
{
"version": "v2",
"created": "Thu, 28 Dec 2006 18:27:48 GMT"
}
]
| 2011-05-12T00:00:00 | [
[
"Harshman",
"N. L.",
""
],
[
"Wickramsekara",
"S.",
""
]
]
|
quant-ph/0611231 | Tobias J. Osborne | Tobias J. Osborne | Approximate locality for quantum systems on graphs | 5 pages, 2 figures, corrected typo | Phys. Rev. Lett. 101, 140503 (2008) | 10.1103/PhysRevLett.101.140503 | null | quant-ph | null | In this Letter we make progress on a longstanding open problem of Aaronson
and Ambainis [Theory of Computing 1, 47 (2005)]: we show that if A is the
adjacency matrix of a sufficiently sparse low-dimensional graph then the
unitary operator e^{itA} can be approximated by a unitary operator U(t) whose
sparsity pattern is exactly that of a low-dimensional graph which gets more
dense as |t| increases. Secondly, we show that if U is a sparse unitary
operator with a gap \Delta in its spectrum, then there exists an approximate
logarithm H of U which is also sparse. The sparsity pattern of H gets more
dense as 1/\Delta increases. These two results can be interpreted as a way to
convert between local continuous-time and local discrete-time processes. As an
example we show that the discrete-time coined quantum walk can be realised as
an approximately local continuous-time quantum walk. Finally, we use our
construction to provide a definition for a fractional quantum fourier
transform.
| [
{
"version": "v1",
"created": "Wed, 22 Nov 2006 17:28:56 GMT"
},
{
"version": "v2",
"created": "Thu, 23 Nov 2006 16:15:57 GMT"
}
]
| 2008-10-06T00:00:00 | [
[
"Osborne",
"Tobias J.",
""
]
]
|
quant-ph/0611232 | Jeremie Fulconis | Jeremie Fulconis, Olivier Alibart, Jeremy L. O'Brien, William J.
Wadsworth, John G. Rarity | Photonic crystal fibre source of photon pairs for quantum information
processing | 4 pages, 3 figures | Phys. Rev. Lett. 99, 120501 (2007) | 10.1103/PhysRevLett.99.120501 | null | quant-ph | null | We demonstrate two key components for optical quantum information processing:
a bright source of heralded single photons; and a bright source of entangled
photon pairs. A pair of pump photons produces a correlated pair of photons at
widely spaced wavelengths (583 nm and 900 nm), via a $\chi^{(3)}$ four-wave
mixing process. We demonstrate a non-classical interference between heralded
photons from independent sources with a visibility of 95%, and an entangled
photon pair source, with a fidelity of 89% with a Bell state.
| [
{
"version": "v1",
"created": "Wed, 22 Nov 2006 18:34:48 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Fulconis",
"Jeremie",
""
],
[
"Alibart",
"Olivier",
""
],
[
"O'Brien",
"Jeremy L.",
""
],
[
"Wadsworth",
"William J.",
""
],
[
"Rarity",
"John G.",
""
]
]
|
quant-ph/0611233 | Matthew Saul Leifer | M. S. Leifer | Conditional Density Operators and the Subjectivity of Quantum Operations | 10 Pages, Work presented at "Foundations of Probability and
Physics-4", Vaxjo University, June 4-9 2006 | G. Adenier, C. A. Fuchs and A. Yu. Khrennikov (eds.), Foundations
of Probability and Physics - 4, AIP Conference Proceedings vol. 889, (AIP
2007), pp. 172-186 | 10.1063/1.2713456 | null | quant-ph | null | Assuming that quantum states, including pure states, represent subjective
degrees of belief rather than objective properties of systems, the question of
what other elements of the quantum formalism must also be taken as subjective
is addressed. In particular, we ask this of the dynamical aspects of the
formalism, such as Hamiltonians and unitary operators. Whilst some operations,
such as the update maps corresponding to a complete projective measurement,
must be subjective, the situation is not so clear in other cases. Here, it is
argued that all trace preserving completely positive maps, including unitary
operators, should be regarded as subjective, in the same sense as a classical
conditional probability distribution. The argument is based on a reworking of
the Choi-Jamiolkowski isomorphism in terms of "conditional" density operators
and trace preserving completely positive maps, which mimics the relationship
between conditional probabilities and stochastic maps in classical probability.
| [
{
"version": "v1",
"created": "Wed, 22 Nov 2006 18:15:30 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Leifer",
"M. S.",
""
]
]
|
quant-ph/0611234 | Gus Gutoski | Gus Gutoski and John Watrous | Toward a general theory of quantum games | 23 pages, 12pt font, single-column compilation of STOC 2007 final
version | Proceedings of STOC 2007, pages 565-574 | 10.1145/1250790.1250873 | null | quant-ph cs.CC cs.GT | null | We study properties of quantum strategies, which are complete specifications
of a given party's actions in any multiple-round interaction involving the
exchange of quantum information with one or more other parties. In particular,
we focus on a representation of quantum strategies that generalizes the
Choi-Jamio{\l}kowski representation of quantum operations. This new
representation associates with each strategy a positive semidefinite operator
acting only on the tensor product of its input and output spaces. Various facts
about such representations are established, and two applications are discussed:
the first is a new and conceptually simple proof of Kitaev's lower bound for
strong coin-flipping, and the second is a proof of the exact characterization
QRG = EXP of the class of problems having quantum refereed games.
| [
{
"version": "v1",
"created": "Wed, 22 Nov 2006 21:05:24 GMT"
},
{
"version": "v2",
"created": "Mon, 2 Apr 2007 19:43:20 GMT"
}
]
| 2013-10-16T00:00:00 | [
[
"Gutoski",
"Gus",
""
],
[
"Watrous",
"John",
""
]
]
|
quant-ph/0611235 | Taehyun Kim | Taehyun Kim, Ingo Stork genannt Wersborg, Franco N. C. Wong, and
Jeffrey H. Shapiro | Complete physical simulation of the entangling-probe attack on the BB84
protocol | 4 pages, 5 figures | Phys. Rev. A 75, 042327 (2007) | 10.1103/PhysRevA.75.042327 | null | quant-ph | null | We have used deterministic single-photon two qubit (SPTQ) quantum logic to
implement the most powerful individual-photon attack against the
Bennett-Brassard 1984 (BB84) quantum key distribution protocol. Our measurement
results, including physical source and gate errors, are in good agreement with
theoretical predictions for the Renyi information obtained by Eve as a function
of the errors she imparts to Alice and Bob's sifted key bits. The current
experiment is a physical simulation of a true attack, because Eve has access to
Bob's physical receiver module. This experiment illustrates the utility of an
efficient deterministic quantum logic for performing realistic physical
simulations of quantum information processing functions.
| [
{
"version": "v1",
"created": "Thu, 23 Nov 2006 05:40:32 GMT"
}
]
| 2024-03-26T00:00:00 | [
[
"Kim",
"Taehyun",
""
],
[
"Wersborg",
"Ingo Stork genannt",
""
],
[
"Wong",
"Franco N. C.",
""
],
[
"Shapiro",
"Jeffrey H.",
""
]
]
|
quant-ph/0611236 | Jacques Vigue | Marion Jacquey (LCAR), Matthias B\"uchner (LCAR), G\'erard Tr\'enec
(LCAR), Jacques Vigu\'e (LCAR) | First measurements of the index of refraction of gases for lithium
atomic waves | null | null | 10.1103/PhysRevLett.98.240405 | null | quant-ph | null | We report here the first measurements of the index of refraction of gases for
lithium waves. Using an atom interferometer, we have measured the real and
imaginary part of the index of refraction $n$ for argon, krypton and xenon, as
a function of the gas density for several velocities of the lithium beam. The
linear dependence of $(n-1)$ with the gas density is well verified. The total
collision cross-section deduced from the imaginary part is in very good
agreement with traditional measurements of this quantity. Finally, as predicted
by theory, the real and imaginary parts of $(n-1)$ and their ratio $\rho$
exhibit glory oscillations.
| [
{
"version": "v1",
"created": "Thu, 23 Nov 2006 07:57:16 GMT"
},
{
"version": "v2",
"created": "Tue, 15 May 2007 14:43:19 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Jacquey",
"Marion",
"",
"LCAR"
],
[
"Büchner",
"Matthias",
"",
"LCAR"
],
[
"Trénec",
"Gérard",
"",
"LCAR"
],
[
"Vigué",
"Jacques",
"",
"LCAR"
]
]
|
quant-ph/0611237 | Dominic Horsman | Dominic Horsman and Vlatko Vedral | Entanglement without nonlocality | 9 pages. Expanded introduction and sections on physical entanglement
and locality | Phys. Rev. A 76, 062319 (2007) | 10.1103/PhysRevA.76.062319 | null | quant-ph | null | We consider the characterization of entanglement from the perspective of a
Heisenberg formalism. We derive an original two-party generalized separability
criteria, and from this describe a novel physical understanding of
entanglement. We find that entanglement may be considered as fundamentally a
local effect, and therefore as a separable computational resource from
nonlocality. We show how entanglement differs from correlation physically, and
explore the implications of this new conception of entanglement for the notion
of classicality. We find that this understanding of entanglement extends
naturally to multipartite cases.
| [
{
"version": "v1",
"created": "Thu, 23 Nov 2006 14:01:47 GMT"
},
{
"version": "v2",
"created": "Wed, 14 Feb 2007 13:07:27 GMT"
},
{
"version": "v3",
"created": "Thu, 30 Aug 2007 14:36:43 GMT"
}
]
| 2023-04-21T00:00:00 | [
[
"Horsman",
"Dominic",
""
],
[
"Vedral",
"Vlatko",
""
]
]
|
quant-ph/0611238 | Christian Brouder | Christian Brouder (IMPMC) | Analytical solutions for two-level systems with damping | 4 pages | Journal of Physics Condensed Matter 40, 31 (2007) 9455 | 10.1088/1751-8113/40/31/020 | null | quant-ph | null | A method is proposed to transform any analytic solution of the Bloch equation
into an analytic solution of the Landau-Lifshitz-Gilbert equation. This allows
for the analytical description of the dynamics of a two level system with
damping. This method shows that damping turns the linear Schr\"{o}dinger
equation of a two-level system into a nonlinear Schr\"{o}dinger equation. As
applications, it is shown that damping has a relatively mild influence on
self-induced transparency but destroys dynamical localization.
| [
{
"version": "v1",
"created": "Thu, 23 Nov 2006 14:08:29 GMT"
}
]
| 2010-07-26T00:00:00 | [
[
"Brouder",
"Christian",
"",
"IMPMC"
]
]
|
quant-ph/0611239 | Anupam Das | Dharmesh Jain, A. Das, Sayan Kar | Path integrals and wavepacket evolution for damped mechanical systems | 15 pages, 6 figures | AJP 75 (2007) 259 | 10.1119/1.2423040 | null | quant-ph | null | Damped mechanical systems with various forms of damping are quantized using
the path integral formalism. In particular, we obtain the path integral kernel
for the linearly damped harmonic oscillator and a particle in a uniform
gravitational field with linearly or quadratically damped motion. In each case,
we study the evolution of Gaussian wavepackets and discuss the characteristic
features that help us distinguish between different types of damping. For
quadratic damping, we show that the action and equation of motion of such a
system has a connection with the zero dimensional version of a currently
popular scalar field theory. Furthermore we demonstrate that the equation of
motion (for quadratic damping) can be identified as a geodesic equation in a
fictitious two-dimensional space.
| [
{
"version": "v1",
"created": "Thu, 23 Nov 2006 15:48:40 GMT"
}
]
| 2012-09-20T00:00:00 | [
[
"Jain",
"Dharmesh",
""
],
[
"Das",
"A.",
""
],
[
"Kar",
"Sayan",
""
]
]
|
quant-ph/0611240 | Sebastian Hofferberth | S. Hofferberth, B. Fischer, T. Schumm, J. Schmiedmayer, and I.
Lesanovsky | Ultracold atoms in radio-frequency-dressed potentials beyond the
rotating wave approximation | 6 pages, 4 figures | Phys. Rev. A 76, 013401 (2007) | 10.1103/PhysRevA.76.013401 | null | quant-ph | null | We study dressed Bose-Einstein condensates in an atom chip radio-frequency
trap. We show that in this system sufficiently strong dressing can be achieved
to cause the widely used rotating wave approximation (RWA) to break down. We
present a full calculation of the atom - field coupling which shows that the
non-RWA contributions quantitatively alter the shape of the emerging dressed
adiabatic potentials. The non-RWA contributions furthermore lead to additional
allowed transitions between dressed levels. We use RF spectroscopy of
Bose-Einstein condensates trapped in the dressed state potentials to directly
observe the transition from the RWA to the beyond-RWA regime.
| [
{
"version": "v1",
"created": "Thu, 23 Nov 2006 17:14:24 GMT"
},
{
"version": "v2",
"created": "Wed, 1 Aug 2007 08:56:09 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Hofferberth",
"S.",
""
],
[
"Fischer",
"B.",
""
],
[
"Schumm",
"T.",
""
],
[
"Schmiedmayer",
"J.",
""
],
[
"Lesanovsky",
"I.",
""
]
]
|
quant-ph/0611241 | Nadav Yoran | Nadav Yoran and Anthony J. Short | Efficient classical simulation of the approximate quantum Fourier
transform | 5 pages, 3 figures | Phys. Rev. A 76, 042321 (2007). | 10.1103/PhysRevA.76.042321 | null | quant-ph | null | We present a method for classically simulating quantum circuits based on the
tensor contraction model of Markov and Shi (quant-ph/0511069). Using this
method we are able to classically simulate the approximate quantum Fourier
transform in polynomial time. Moreover, our approach allows us to formulate a
condition for the composability of simulable quantum circuits. We use this
condition to show that any circuit composed of a constant number of approximate
quantum Fourier transform circuits and log-depth circuits with limited
interaction range can also be efficiently simulated.
| [
{
"version": "v1",
"created": "Thu, 23 Nov 2006 17:38:37 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Yoran",
"Nadav",
""
],
[
"Short",
"Anthony J.",
""
]
]
|
quant-ph/0611242 | Davide Rossini | Davide Rossini, Tommaso Calarco, Vittorio Giovannetti, Simone
Montangero, Rosario Fazio | Decoherence induced by interacting quantum spin baths | 18 pages, 20 figures | Phys. Rev. A 75, 032333 (2007) | 10.1103/PhysRevA.75.032333 | null | quant-ph cond-mat.other | null | We study decoherence induced on a two-level system coupled to a
one-dimensional quantum spin chain. We consider the cases where the dynamics of
the chain is determined by the Ising, XY, or Heisenberg exchange Hamiltonian.
This model of quantum baths can be of fundamental importance for the
understanding of decoherence in open quantum systems, since it can be
experimentally engineered by using atoms in optical lattices. As an example,
here we show how to implement a pure dephasing model for a qubit system coupled
to an interacting spin bath. We provide results that go beyond the case of a
central spin coupled uniformly to all the spins of the bath, in particular
showing what happens when the bath enters different phases, or becomes
critical; we also study the dependence of the coherence loss on the number of
bath spins to which the system is coupled and we describe a
coupling-independent regime in which decoherence exhibits universal features,
irrespective of the system-environment coupling strength. Finally, we establish
a relation between decoherence and entanglement inside the bath. For the Ising
and the XY models we are able to give an exact expression for the decay of
coherences, while for the Heisenberg bath we resort to the numerical
time-dependent Density Matrix Renormalization Group.
| [
{
"version": "v1",
"created": "Thu, 23 Nov 2006 17:36:36 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Rossini",
"Davide",
""
],
[
"Calarco",
"Tommaso",
""
],
[
"Giovannetti",
"Vittorio",
""
],
[
"Montangero",
"Simone",
""
],
[
"Fazio",
"Rosario",
""
]
]
|
quant-ph/0611243 | Michael Bordag | M.Bordag | Generalized Lifshitz formula for a cylindrical plasma sheet in front of
a plane beyond proximity force approximation | 35 pages, 8 figures | Phys.Rev.D75:065003,2007 | 10.1103/PhysRevD.75.065003 | null | quant-ph hep-th | null | We calculate the first correction beyond proximity force approximation for a
cylindrical graphene sheet in interaction with a flat graphene sheet or a
dielectric half space.
| [
{
"version": "v1",
"created": "Thu, 23 Nov 2006 20:05:39 GMT"
},
{
"version": "v2",
"created": "Fri, 24 Nov 2006 22:56:38 GMT"
}
]
| 2008-11-26T00:00:00 | [
[
"Bordag",
"M.",
""
]
]
|
quant-ph/0611244 | Alexander I. Lvovsky | Jaroslav Rehacek, Zdenek Hradil, E. Knill, A. I. Lvovsky | Diluted maximum-likelihood algorithm for quantum tomography | v2: Convergence proof added | Physical Review A 75, 042108 (2007) | 10.1103/PhysRevA.75.042108 | null | quant-ph | null | We propose a refined iterative likelihood-maximization algorithm for
reconstructing a quantum state from a set of tomographic measurements. The
algorithm is characterized by a very high convergence rate and features a
simple adaptive procedure that ensures likelihood increase in every iteration
and convergence to the maximum-likelihood state.
We apply the algorithm to homodyne tomography of optical states and quantum
tomography of entangled spin states of trapped ions and investigate its
convergence properties.
| [
{
"version": "v1",
"created": "Thu, 23 Nov 2006 22:36:04 GMT"
},
{
"version": "v2",
"created": "Thu, 22 Feb 2007 18:48:03 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Rehacek",
"Jaroslav",
""
],
[
"Hradil",
"Zdenek",
""
],
[
"Knill",
"E.",
""
],
[
"Lvovsky",
"A. I.",
""
]
]
|
quant-ph/0611245 | Frank Tipler | Frank J. Tipler | What About Quantum Theory? Bayes and the Born Interpretation | null | null | null | null | quant-ph | null | I show that probabilities in quantum mechanics are a measure of belief in the
presence of human ignorance, just like all other probabilities. The Born
interpretation of the square of modulus of the wave function arises from the
interaction of a quantum system with an observer, and probabilities will not
arise unless the observer is unable to access all the information available in
the system's wave function. Quantum mechanics generally does not permit all the
information to be obtained, even in principle, just as in relativity
information from outside the past light cone cannot be obtained. But
probabilities do not imply indeterminism. Instead, quantum mechanics is more
deterministic than classical mechanics.
| [
{
"version": "v1",
"created": "Thu, 23 Nov 2006 23:35:34 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Tipler",
"Frank J.",
""
]
]
|
quant-ph/0611246 | Etienne Brion | E. Brion, L. H. Pedersen, K. Molmer, S. Chutia, M. Saffman | Universal Quantum Computation in a Neutral Atom Decoherence Free
Subspace | 7 pages, 8 figures | Phys. Rev. A 75, 032328 (2007) | 10.1103/PhysRevA.75.032328 | null | quant-ph | null | In this paper, we propose a way to achieve protected universal computation in
a neutral atom quantum computer subject to collective dephasing. Our proposal
relies on the existence of a Decoherence Free Subspace (DFS), resulting from
symmetry properties of the errors. After briefly describing the physical system
and the error model considered, we show how to encode information into the DFS
and build a complete set of safe universal gates. Finally, we provide numerical
simulations for the fidelity of the different gates in the presence of
time-dependent phase errors and discuss their performance and practical
feasibility.
| [
{
"version": "v1",
"created": "Fri, 24 Nov 2006 08:54:44 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Brion",
"E.",
""
],
[
"Pedersen",
"L. H.",
""
],
[
"Molmer",
"K.",
""
],
[
"Chutia",
"S.",
""
],
[
"Saffman",
"M.",
""
]
]
|
quant-ph/0611247 | Guo-Ping Guo | Guo-Ping Guo, Hui Zhang, Tao Tu, and Guang-Can Guo | One-step preparation of cluster states in quantum dot molecules | 5 pages, 3 figures | Phys. Rev. A 75, 050301(R) 2007 | 10.1103/PhysRevA.75.050301 | null | quant-ph | null | Cluster states, a special type of highly entangled states, are a universal
resource for measurement-based quantum computation. Here, we propose an
efficient one-step generation scheme for cluster states in semiconductor
quantum dot molecules, where qubits are encoded on singlet and triplet state of
two coupled quantum dots. By applying a collective electrical field or
simultaneously adjusting interdot bias voltages of all double-dot molecule, we
get a switchable Ising-like interaction between any two adjacent quantum
molecule qubits. The initialization, the single qubit measurement, and the
experimental parameters are discussed, which shows the large cluster state
preparation and one-way quantum computation implementable in semiconductor
quantum dots with the present techniques.
| [
{
"version": "v1",
"created": "Fri, 24 Nov 2006 09:32:20 GMT"
},
{
"version": "v2",
"created": "Sat, 25 Nov 2006 12:44:27 GMT"
},
{
"version": "v3",
"created": "Fri, 13 Apr 2007 07:52:41 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Guo",
"Guo-Ping",
""
],
[
"Zhang",
"Hui",
""
],
[
"Tu",
"Tao",
""
],
[
"Guo",
"Guang-Can",
""
]
]
|
quant-ph/0611248 | Arul Lakshminarayan | J. Karthik, Auditya Sharma, and Arul Lakshminarayan | Entanglement, avoided crossings and quantum chaos in an Ising model with
a tilted magnetic field | Corrections in two figure captions and one new reference. To appear
in Phys. Rev. A | Phys. Rev. A 75, 022304 (2007) | 10.1103/PhysRevA.75.022304 | null | quant-ph cond-mat.other nlin.CD | null | We study a one-dimensional Ising model with a magnetic field and show that
tilting the field induces a transition to quantum chaos. We explore the
stationary states of this Hamiltonian to show the intimate connection between
entanglement and avoided crossings. In general entanglement gets exchanged
between the states undergoing an avoided crossing with an overall enhancement
of multipartite entanglement at the closest point of approach, simultaneously
accompanied by diminishing two-body entanglement as measured by concurrence. We
find that both for stationary as well as nonstationary states, nonintegrability
leads to a destruction of two-body correlations and distributes entanglement
more globally.
| [
{
"version": "v1",
"created": "Fri, 24 Nov 2006 11:11:56 GMT"
},
{
"version": "v2",
"created": "Mon, 29 Jan 2007 15:01:30 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Karthik",
"J.",
""
],
[
"Sharma",
"Auditya",
""
],
[
"Lakshminarayan",
"Arul",
""
]
]
|
quant-ph/0611249 | Konstanze J\"ahne | K. Jahne, B. Yurke, U. Gavish | High fidelity transfer of an arbitrary quantum state between harmonic
oscillators | 4 pages, 1 figure | Phys. Rev. A 75, 010301(R) (2007) | 10.1103/PhysRevA.75.010301 | null | quant-ph cond-mat.other | null | It is shown that by switching a specific time-dependent interaction between a
harmonic oscillator and a transmission line (a waveguide, an optical fiber,
etc.) the quantum state of the oscillator can be transferred into that of
another oscillator coupled to the distant other end of the line, with a
fidelity that is independent of the initial state of both oscillators. For a
transfer time $T$, the fidelity approaches 1 exponentially in $\gamma T$ where
$\gamma$ is a characteristic damping rate. Hence, a good fidelity is achieved
even for a transfer time of a few damping times. Some implementations are
discussed.
| [
{
"version": "v1",
"created": "Fri, 24 Nov 2006 11:27:44 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Jahne",
"K.",
""
],
[
"Yurke",
"B.",
""
],
[
"Gavish",
"U.",
""
]
]
|
quant-ph/0611250 | Miroljub Dugic m | M. Dugic, J. Jeknic-Dugic | What is "system": the information-theoretic arguments | 13 pages, no figures | Int J Theor Phys (2008) 47: 805-813 | 10.1007/s10773-007-9504-1 | null | quant-ph | null | The problem of "what is 'system'?" is in the very foundations of modern
quantum mechanics. Here, we point out the interest in this topic in the
information-theoretic context. E.g., we point out the possibility to manipulate
a pair of mutually non-interacting, non-entangled systems to employ
entanglement of the newly defined '(sub)systems' consisting the one and the
same composite system. Given the different divisions of a composite system into
"subsystems", the Hamiltonian of the system may perform in general
non-equivalent quantum computations. Redefinition of "subsystems" of a
composite system may be regarded as a method for avoiding decoherence in the
quantum hardware. In principle, all the notions refer to a composite system as
simple as the hydrogen atom.
| [
{
"version": "v1",
"created": "Fri, 24 Nov 2006 13:23:23 GMT"
}
]
| 2012-02-21T00:00:00 | [
[
"Dugic",
"M.",
""
],
[
"Jeknic-Dugic",
"J.",
""
]
]
|
quant-ph/0611251 | Ahmad Ajdarzadeh Oskouei | Hassan Kaatuzian, AliAkbar Wahedy Zarch | A Nano-Quantum Photonic Model for Justification of Dispersion in Single
Crystal Film of NPP | 15 pages must be reduced to 8 pages | null | null | null | quant-ph | null | In this paper, we present a nano-quantum photonic model for justification of
normal dispersion in a thin crystal film of NPP. In this method, we assume a
laser beam consists of a flow of energetic particles. By precise analyzing of
photon interaction with pi-electron system of benzene ring in NPP crystal, we
will attain refractive index (RI) in any wavelength and compare the results
with experimental data.
| [
{
"version": "v1",
"created": "Fri, 24 Nov 2006 13:42:59 GMT"
},
{
"version": "v2",
"created": "Tue, 28 Nov 2006 13:06:20 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Kaatuzian",
"Hassan",
""
],
[
"Zarch",
"AliAkbar Wahedy",
""
]
]
|
quant-ph/0611252 | Peter Stelmachovic | Peter Stelmachovic, Marian Rosko | Local control of remote entanglement | null | null | null | null | quant-ph | null | We address the problem of the generation of entanglement. We focus on the
control of entanglement shared by two non-interacting parties $A$ and $C$ via
interaction with a third party $B$. We show that, for certain physical models,
it is possible to have an asymptotically complete control of the entanglement
shared by $A$ and $C$ by changing parameters of the Hamiltonian local at site
$B$. We present an example where different models (propositions) of physical
situation, that lead to different descriptions of the system $B$, result into
different amount entanglement produced. In the end we discuss limits of the
procedure.
| [
{
"version": "v1",
"created": "Fri, 24 Nov 2006 15:40:41 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Stelmachovic",
"Peter",
""
],
[
"Rosko",
"Marian",
""
]
]
|
quant-ph/0611253 | Peter Stelmachovic | Peter Stelmachovic and Vladimir Buzek | Bounds on action of local quantum channels | null | J. Phys. A: Math. Gen. 38 (2005) p. 6051- 6064 | null | null | quant-ph | null | We derive an upper bound on the action of a direct product of two quantum
maps (channels) acting on multi-partite quantum states. We assume that the
individual channels $\Lambda_j$ affect single-particle states so, that for an
arbitrary input $\rho_j$, the distance $D_j (\Lambda_j [ \rho_j ], \rho_j)$
between the input $\rho_j$ and the output $\Lambda_j [ \rho_j ]$ of the channel
is less than $\epsilon$. Given this assumption we show that for an arbitrary
{\em separable} two-partite state $\rho_{12}$ the distance between the input
$\rho_{12}$ and the output $\Lambda_1\otimes\Lambda_2[\rho_{12} ]$ fulfills the
bound $D_{12} (\Lambda_1 \otimes \Lambda_2 [ \rho_{12} ], \rho_{12}) \leq
\sqrt{2+ 2 \sqrt{(1-1/d_1)(1-1/d_2)}} \epsilon$ where $d_1$ and $d_2$ are
dimensions of first and second quantum system respectively. On the contrary,
entangled states are transformed in such a way, that the bound on the action of
the local channels is $D_{12} (\Lambda_1 \otimes \Lambda_2 [ \rho_{12} ],
\rho_{12}) \leq 2 \sqrt{2 - 1/d} \: \epsilon$, where $d$ is the dimension of
the smaller of the two quantum systems passing through the channels. Our
results show that the fundamental distinction between the set of separable and
the set of entangled states results into two different bounds which in turn can
be exploited for a discrimination between the two sets of states. We generalize
our results to multi-partite channels.
| [
{
"version": "v1",
"created": "Fri, 24 Nov 2006 15:54:32 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Stelmachovic",
"Peter",
""
],
[
"Buzek",
"Vladimir",
""
]
]
|
quant-ph/0611254 | Paulo Valente | L. S. Cruz, D. Felinto, J. G. Aguirre G\'omez, M. Martinelli, P.
Valente, A. Lezama, and P. Nussenzveig | Laser-noise-induced correlations and anti-correlations in
Electromagnetically Induced Transparency | Accepted for publication in EPJ D | null | 10.1140/epjd/e2006-00254-4 | null | quant-ph | null | High degrees of intensity correlation between two independent lasers were
observed after propagation through a rubidium vapor cell in which they generate
Electromagnetically Induced Transparency (EIT). As the optical field
intensities are increased, the correlation changes sign (becoming
anti-correlation). The experiment was performed in a room temperature rubidium
cell, using two diode lasers tuned to the $^{85}$Rb $D_2$ line ($\lambda =
780$nm). The cross-correlation spectral function for the pump and probe fields
is numerically obtained by modeling the temporal dynamics of both field phases
as diffusing processes. We explored the dependence of the atomic response on
the atom-field Rabi frequencies, optical detuning and Doppler width. The
results show that resonant phase-noise to amplitude-noise conversion is at the
origin of the observed signal and the change in sign for the correlation
coefficient can be explained as a consequence of the competition between EIT
and Raman resonance processes.
| [
{
"version": "v1",
"created": "Fri, 24 Nov 2006 20:29:57 GMT"
}
]
| 2016-08-14T00:00:00 | [
[
"Cruz",
"L. S.",
""
],
[
"Felinto",
"D.",
""
],
[
"Gómez",
"J. G. Aguirre",
""
],
[
"Martinelli",
"M.",
""
],
[
"Valente",
"P.",
""
],
[
"Lezama",
"A.",
""
],
[
"Nussenzveig",
"P.",
""
]
]
|
quant-ph/0611255 | Sara Rombetto | Yu.N.Ovchinnikov, S.Rombetto, B.Ruggiero, V.Corato, P.Silvestrini | Resonance phenomena in Macroscopic Quantum Tunneling: the small
viscosity limit | 10 figures | null | null | null | quant-ph | null | We present a new theoretical approach to describe the quantum behavior of a
macroscopic system interacting with an external irradiation field, close to the
resonant condition. Here we consider the extremely underdamped regime for a
system described by a double well potential. The theory includes both:
transitions from one well to the other and relaxation processes. We simulate
resonant phenomena in a rf-SQUID, whose parameters lie in the range typically
used in the experiments. The dependence of the transition probability W on the
external drive of the system $\phi_x$ shows three resonance peaks. One peak is
connected with the resonant tunneling and the two others with the resonant
pumping. The relative position of the two peaks correlated to the resonant
pumping depends on the pumping frequency $\nu$ and on the system parameters.
The preliminary measurements on our devices show a low dissipation level and
assure that they are good candidates in order to realize new experiments on the
resonant phenomena in the presence of an external microwave irradiation of
proper frequency.
| [
{
"version": "v1",
"created": "Sat, 25 Nov 2006 09:36:08 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Ovchinnikov",
"Yu. N.",
""
],
[
"Rombetto",
"S.",
""
],
[
"Ruggiero",
"B.",
""
],
[
"Corato",
"V.",
""
],
[
"Silvestrini",
"P.",
""
]
]
|
quant-ph/0611256 | Mohamad Ali Jafarizadeh | M. A. Jafarizadeh, G. Najarbashi, H. Habibian | Manipulating Multi-qudit Entanglement Witnesses by Using Linear
Programming | 29 pages, 4 figures | null | 10.1103/PhysRevA.75.052326 | null | quant-ph | null | A new class of entanglement witnesses (EWs) called reduction type
entanglement witnesses is introduced, which can detect some multi-qudit
entangeled states including PPT ones with Hilbert space of dimension
$d_{_{1}}\otimes d_{_{2}}\otimes...\otimes d_{_{n}}$. The novelty of this work
comes from the fact that the feasible regions turn out to be convex polygons,
hence the manipulation of these EWs reduces to linear programming which can be
solved \emph{exactly} by using simplex method. The decomposability and
non-decomposability of these EWs are studied and it is shown that it has a
close connection with eigenvalues and optimality of EWs. Also using the Jamio\l
kowski isomorphism, the corresponding possible positive maps, including the
generalized reduction maps of Ref. \cite{Hall1}, are obtained.
| [
{
"version": "v1",
"created": "Sat, 25 Nov 2006 17:57:26 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Jafarizadeh",
"M. A.",
""
],
[
"Najarbashi",
"G.",
""
],
[
"Habibian",
"H.",
""
]
]
|
quant-ph/0611257 | Gert-Ludwig Ingold | Stefan Schenk, Gert-Ludwig Ingold | Relation between phase space coverage and entanglement for spin-1/2
systems | 6 pages, 2 figures, RevTeX format | Phys. Rev. A 75, 022328 (2007) | 10.1103/PhysRevA.75.022328 | null | quant-ph | null | For systems of two and three spins 1/2 it is known that the second moment of
the Husimi function can be related to entanglement properties of the
corresponding states. Here, we generalize this relation to an arbitrary number
of spins in a pure state. It is shown that the second moment of the Husimi
function can be expressed in terms of the lengths of the concurrence vectors
for all possible partitions of the N-spin system in two subsystems. This
relation implies that the phase space distribution of an entangled state is
less localized than that of a non-entangled state. As an example, the second
moment of the Husimi function is analyzed for an Ising chain subject to a
magnetic field perpendicular to the chain axis.
| [
{
"version": "v1",
"created": "Mon, 27 Nov 2006 13:32:54 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Schenk",
"Stefan",
""
],
[
"Ingold",
"Gert-Ludwig",
""
]
]
|
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