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2025-04-04 00:00:00
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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
quant-ph/0606088
|
Jiankui He
|
Jiankui He, Qing Chen, Lei Ding, Shao-Long Wan
|
Conclusive quantum-state transfer with a single randomly coupled spin
chain
|
13 pages, 3 figures
| null | null | null |
quant-ph
| null |
We studied the quantum state transfer in randomly coupled spin chains. By
using local memories storing the information and dividing the task into
transfer portion and decoding portion, conclusive transfer was ingeniously
achieved with just one single spin chain. In our scheme, the probability of
successful transfer can be made arbitrary close to unity. Especially, our
scheme is a good protocol to decode information from memories without adding
another spin chain. Compared with Time-reversed protocol, the average decoding
time is much less in our scheme.
|
[
{
"version": "v1",
"created": "Fri, 9 Jun 2006 15:23:34 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"He",
"Jiankui",
""
],
[
"Chen",
"Qing",
""
],
[
"Ding",
"Lei",
""
],
[
"Wan",
"Shao-Long",
""
]
] |
quant-ph/0606089
|
Jeremy Levy
|
Vanita Srinivasa, Jeremy Levy, C. Stephen Hellberg
|
Flying Spin Qubits
|
13 pages, 4 figures. Revised manuscript in response to reviewer
comments
| null | null | null |
quant-ph
| null |
We present a method for encoding and transporting qubits within a dimerized
Heisenberg spin-1/2 chain. Logical qubits are localized at the domain walls
that separate the two possible dimerized states. The domain walls can be moved
to produce "flying spin qubits". The topological nature of these states makes
them stable against a wide class of perturbations. Pairs of domain walls can be
used to generate Einstein-Podolsky-Rosen pairs of entangled qubits. We discuss
speed limitations within an exactly solvable three-spin model and describe a
possible physical realization using quantum dot arrays.
|
[
{
"version": "v1",
"created": "Fri, 9 Jun 2006 18:12:18 GMT"
},
{
"version": "v2",
"created": "Sat, 23 Dec 2006 22:21:09 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Srinivasa",
"Vanita",
""
],
[
"Levy",
"Jeremy",
""
],
[
"Hellberg",
"C. Stephen",
""
]
] |
quant-ph/0606090
|
Caroline Kruszynska
|
Caroline Kruszynska, Akimasa Miyake, Hans J. Briegel, Wolfgang D\"ur
|
Entanglement purification protocols for all graph states
|
revtex 10 pages, 6 figures
|
Phys. Rev. A 74, 052316 (2006)
|
10.1103/PhysRevA.74.052316
| null |
quant-ph
| null |
We present multiparty entanglement purification protocols that are capable of
purifying arbitrary graph states directly. We develop recurrence and breeding
protocols and compare our methods with strategies based on bipartite
entanglement purification in static and communication scenarios. We find that
direct multiparty purification is of advantage with respect to achievable
yields and minimal required fidelity in static scenarios, and with respect to
obtainable fidelity in the case of noisy operations in both scenarios.
|
[
{
"version": "v1",
"created": "Fri, 9 Jun 2006 19:47:24 GMT"
},
{
"version": "v2",
"created": "Fri, 17 Nov 2006 10:08:35 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Kruszynska",
"Caroline",
""
],
[
"Miyake",
"Akimasa",
""
],
[
"Briegel",
"Hans J.",
""
],
[
"Dür",
"Wolfgang",
""
]
] |
quant-ph/0606091
|
Massimo Tessarotto
|
Massimo Tessarotto, Marco Ellero and Piero Nicolini
|
Inverse kinetic theory for quantum hydrodynamic equations
| null |
Phys.Rev.A75:012105,2007
|
10.1103/PhysRevA.75.012105
| null |
quant-ph
| null |
We propose a solution for the inverse kinetic theory for quantum hydrodynamic
equations associated to the non-relativistic Schr\"{o}dinger equation. It is
shown that an inverse kinetic equation of the form of the Vlasov equation can
be non-uniquely determined under suitable mathematical prescriptions.
|
[
{
"version": "v1",
"created": "Sat, 10 Jun 2006 05:26:01 GMT"
}
] | 2008-11-26T00:00:00 |
[
[
"Tessarotto",
"Massimo",
""
],
[
"Ellero",
"Marco",
""
],
[
"Nicolini",
"Piero",
""
]
] |
quant-ph/0606092
|
Graeme Mitchison
|
Graeme Mitchison and Richard Jozsa
|
The limits of counterfactual computation
|
Hosten et al. have responded to the second version of this paper, and
the present version includes our reply to them. The text is otherwise
unchanged
| null | null | null |
quant-ph
| null |
We show that the protocol recently proposed by Hosten et al. does not allow
all possible results of a computation to be obtained counterfactually, as was
claimed. It only gives a counterfactual outcome for one of the computer
outputs. However, we confirm the observation that the protocol gives some
protection against decoherence. In some situations, though, it may be more
effective simply to run the computer several times.
|
[
{
"version": "v1",
"created": "Sat, 10 Jun 2006 14:30:20 GMT"
},
{
"version": "v2",
"created": "Thu, 27 Jul 2006 15:24:28 GMT"
},
{
"version": "v3",
"created": "Wed, 3 Jan 2007 16:52:02 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Mitchison",
"Graeme",
""
],
[
"Jozsa",
"Richard",
""
]
] |
quant-ph/0606093
|
Bas Janssens
|
Bas Janssens
|
Unifying Decoherence and the Heisenberg Principle
|
17 pages, 7 figures
|
Lett. Math. Phys (2017) 107:1557-1579
|
10.1007/s11005-017-0953-z
| null |
quant-ph
| null |
We exhibit three inequalities involving quantum measurement, all of which are
sharp and state independent. The first inequality bounds the performance of
joint measurement. The second quantifies the trade-off between the measurement
quality and the disturbance caused on the measured system. Finally, the third
inequality provides a sharp lower bound on the amount of decoherence in terms
of the measurement quality. This gives a unified discription of both the
Heisenberg principle and the collapse of the wave function.
|
[
{
"version": "v1",
"created": "Sat, 10 Jun 2006 18:55:14 GMT"
}
] | 2021-08-18T00:00:00 |
[
[
"Janssens",
"Bas",
""
]
] |
quant-ph/0606094
|
Todd Brun
|
Hari Krovi and Todd A. Brun (USC)
|
Quantum walks with infinite hitting times
|
28 pages, 3 figures in EPS format
|
Phys. Rev. A 74, 042334 (2006)
|
10.1103/PhysRevA.74.042334
| null |
quant-ph
| null |
Hitting times are the average time it takes a walk to reach a given final
vertex from a given starting vertex. The hitting time for a classical random
walk on a connected graph will always be finite. We show that, by contrast,
quantum walks can have infinite hitting times for some initial states. We seek
criteria to determine if a given walk on a graph will have infinite hitting
times, and find a sufficient condition, which for discrete time quantum walks
is that the degeneracy of the evolution operator be greater than the degree of
the graph. The set of initial states which give an infinite hitting time form a
subspace. The phenomenon of infinite hitting times is in general a consequence
of the symmetry of the graph and its automorphism group. Using the irreducible
representations of the automorphism group, we derive conditions such that
quantum walks defined on this graph must have infinite hitting times for some
initial states. In the case of the discrete walk, if this condition is
satisfied the walk will have infinite hitting times for any choice of a coin
operator, and we give a class of graphs with infinite hitting times for any
choice of coin. Hitting times are not very well-defined for continuous time
quantum walks, but we show that the idea of infinite hitting-time walks
naturally extends to the continuous time case as well.
|
[
{
"version": "v1",
"created": "Sat, 10 Jun 2006 23:51:35 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Krovi",
"Hari",
"",
"USC"
],
[
"Brun",
"Todd A.",
"",
"USC"
]
] |
quant-ph/0606095
|
Indrani Bose
|
Amit Tribedi and Indrani Bose
|
Entangled spin clusters: some special features
|
17 pages, 6 figures. Accepted in Phys. Rev. A
|
Phys. Rev. A 74, 012314 (2006)
|
10.1103/PhysRevA.74.012314
| null |
quant-ph cond-mat.other
| null |
In this paper, we study three specific aspects of entanglement in small spin
clusters. We first study the effect of inhomogeneous exchange coupling strength
on the entanglement properties of the S=1/2 antiferromagnetic linear chain
tetramer compound NaCuAsO_{4}. The entanglement gap temperature, T_{E}, is
found to have a non-monotonic dependence on the value of $\alpha$, the exchange
coupling inhomogeneity parameter. We next determine the variation of T_{E} as a
function of S for a spin dimer, a trimer and a tetrahedron. The temperature
T_{E} is found to increase as a function of S, but the scaled entanglement gap
temperature t_{E} goes to zero as S becomes large. Lastly, we study a spin-1
dimer compound to illustrate the quantum complementarity relation. We show that
in the experimentally realizable parameter region, magnetization and
entanglement plateaus appear simultaneously at low temperatures as a function
of the magnetic field. Also, the sharp increase in one quantity as a function
of the magnetic field is accompanied by a sharp decrease in the other so that
the quantum complementarity relation is not violated.
|
[
{
"version": "v1",
"created": "Mon, 12 Jun 2006 08:30:40 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Tribedi",
"Amit",
""
],
[
"Bose",
"Indrani",
""
]
] |
quant-ph/0606096
|
Daniela Dragoman
|
Daniela Dragoman
|
Photon States from Propagating Complex Electromagnetic Fields
| null | null |
10.1364/JOSAB.24.000922
| null |
quant-ph
| null |
A wavefunction for single- and many-photon states is defined by associating
photons with different momenta to different spectral and polarization
components of the classical, generally complex, electromagnetic field that
propagates in a definite direction. By scaling each spectral component of the
classical field to the square root of the photon energy, the appropriately
normalized photon wavefunction acquires the desired interpretation of
probability density amplitude, in contradistinction to the Riemann-Silbertsein
wavefunction that can be considered as the amplitude of the photon probability
energy density.
|
[
{
"version": "v1",
"created": "Mon, 12 Jun 2006 10:26:43 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Dragoman",
"Daniela",
""
]
] |
quant-ph/0606097
|
Michael Hartmann Mr
|
Michael J. Hartmann, Fernando G.S.L. Brandao and Martin B. Plenio
|
Strongly Interacting Polaritons in Coupled Arrays of Cavities
|
Published in Nature Physics as advance online publication, to appear
in the December issue. This preprint differs from the journal version
|
Nature Physics 2, pp 849 - 855 (2006)
|
10.1038/nphys462
| null |
quant-ph cond-mat.other
| null |
The experimental observation of quantum phenomena in strongly correlated many
particle systems is difficult because of the short length- and timescales
involved. Obtaining at the same time detailed control of individual
constituents appears even more challenging and thus to date inhibits employing
such systems as quantum computing devices. Substantial progress to overcome
these problems has been achieved with cold atoms in optical lattices, where a
detailed control of collective properties is feasible but it is very difficult
to address and hence control or measure individual sites. Here we show, that
polaritons, combined atom and photon excitations, in an array of cavities such
as a photonic crystal or coupled toroidal micro-cavities, can form a strongly
interacting many body system, where individual particles can be controlled and
measured. All individual building blocks of the proposed setting have already
been experimentally realised, thus demonstrating the potential of this device
as a quantum simulator. With the possibility to create attractive on-site
potentials the scheme allows for the creation of highly entangled states and a
phase with particles much more delocalised than in superfluids.
|
[
{
"version": "v1",
"created": "Mon, 12 Jun 2006 18:37:56 GMT"
},
{
"version": "v2",
"created": "Wed, 29 Nov 2006 17:11:35 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Hartmann",
"Michael J.",
""
],
[
"Brandao",
"Fernando G. S. L.",
""
],
[
"Plenio",
"Martin B.",
""
]
] |
quant-ph/0606098
|
Xun-Li Feng
|
Xun-Li Feng, Zisheng Wang, Chunfeng Wu, L.C. Kwek and C.H. Oh
|
A scheme for unconventional geometric quantum computation in cavity QED
|
4 pages, 1 figure
| null |
10.1103/PhysRevA.75.052312
| null |
quant-ph
| null |
We present a scheme for implementing the unconventional geometric two-qubit
phase gate with nonzero dynamical phase by using the two-channel Raman
interaction of two atoms in a cavity. We show that the dynamical phase acquired
in a cyclic evolution is proportional to the geometric phase acquired in the
same cyclic evolution, hence the the total phase possesses the same geometric
features as the geometric phase. In our scheme the atomic excited state is
adiabatically eliminated and the operation of the proposed logic gate involves
only in the metastable states of the atom and hence is not affected by
spontaneous emission.
|
[
{
"version": "v1",
"created": "Mon, 12 Jun 2006 13:00:06 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Feng",
"Xun-Li",
""
],
[
"Wang",
"Zisheng",
""
],
[
"Wu",
"Chunfeng",
""
],
[
"Kwek",
"L. C.",
""
],
[
"Oh",
"C. H.",
""
]
] |
quant-ph/0606099
|
Eran Segev
|
Eran Arbel-Segev, Baleegh Abdo, Oleg Shtempluck, Eyal Buks, Bernard
Yurke
|
Prospects of employing superconducting stripline resonators for studying
the dynamical Casimir effect experimentally
|
4 pages, 2 figures
| null | null | null |
quant-ph
| null |
We discuss the prospects of employing an NbN superconducting microwave
stripline resonator for studying the dynamical Casimir effect experimentally.
Preliminary experimental results, in which optical illumination is employed for
modulating the resonance frequencies of the resonator, show that such a system
is highly promising for this purpose. Moreover, we discuss the undesirable
effect of heating which results from the optical illumination, and show that
degradation in noise properties can be minimized by employing an appropriate
design.
|
[
{
"version": "v1",
"created": "Mon, 12 Jun 2006 18:56:17 GMT"
},
{
"version": "v2",
"created": "Tue, 13 Jun 2006 18:54:21 GMT"
},
{
"version": "v3",
"created": "Sun, 3 Sep 2006 13:23:16 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Arbel-Segev",
"Eran",
""
],
[
"Abdo",
"Baleegh",
""
],
[
"Shtempluck",
"Oleg",
""
],
[
"Buks",
"Eyal",
""
],
[
"Yurke",
"Bernard",
""
]
] |
quant-ph/0606100
|
Andrzej Deloff
|
A. Deloff
|
Semi-spectral Chebyshev method in Quantum Mechanics
|
RevTeX, 12 EPS figures
|
AnnalsPhys.322:1373-1419,2007
|
10.1016/j.aop.2006.07.004
| null |
quant-ph nucl-th
| null |
Traditionally, finite differences and finite element methods have been by
many regarded as the basic tools for obtaining numerical solutions in a variety
of quantum mechanical problems emerging in atomic, nuclear and particle
physics, astrophysics, quantum chemistry, etc. In recent years, however, an
alternative technique based on the semi-spectral methods has focused
considerable attention. The purpose of this work is first to provide the
necessary tools and subsequently examine the efficiency of this method in
quantum mechanical applications. Restricting our interest to time independent
two-body problems, we obtained the continuous and discrete spectrum solutions
of the underlying Schroedinger or Lippmann-Schwinger equations in both, the
coordinate and momentum space. In all of the numerically studied examples we
had no difficulty in achieving the machine accuracy and the semi-spectral
method showed exponential convergence combined with excellent numerical
stability.
|
[
{
"version": "v1",
"created": "Mon, 12 Jun 2006 20:40:37 GMT"
}
] | 2008-11-26T00:00:00 |
[
[
"Deloff",
"A.",
""
]
] |
quant-ph/0606101
|
Sumanta Tewari
|
Sumanta Tewari, S. Das Sarma, Chetan Nayak, Chuanwei Zhang, P. Zoller
|
Quantum Computation Using Vortices and Majorana Zero Modes of a $p_x$ +
$ip_y$ Superfluid of Fermionic Cold Atoms
| null |
Phys. Rev. Lett. 98, 010506 (2007)
|
10.1103/PhysRevLett.98.010506
| null |
quant-ph cond-mat.mes-hall
| null |
We propose to use the recently predicted two-dimensional `weak-pairing' $p_x
+ ip_y$ superfluid state of fermionic cold atoms as a platform for topological
quantum computation. In the core of a vortex, this state supports a zero-energy
Majorana mode, which moves to finite energy in the corresponding topologically
trivial `strong-pairing' state. By braiding vortices in the `weak-pairing'
state, unitary quantum gates can be applied to the Hilbert space of Majorana
zero-modes. For read-out of the topological qubits, we propose realistic
schemes suitable for atomic superfluids.
|
[
{
"version": "v1",
"created": "Mon, 12 Jun 2006 21:57:28 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Tewari",
"Sumanta",
""
],
[
"Sarma",
"S. Das",
""
],
[
"Nayak",
"Chetan",
""
],
[
"Zhang",
"Chuanwei",
""
],
[
"Zoller",
"P.",
""
]
] |
quant-ph/0606102
|
Andrew Scott
|
A. J. Scott, Todd A. Brun, Carlton M. Caves, Ruediger Schack
|
Hypersensitivity and chaos signatures in the quantum baker's maps
|
32 pages, 6 figures
|
J. Phys. A 39, 13405 (2006)
|
10.1088/0305-4470/39/43/002
| null |
quant-ph nlin.CD
| null |
Classical chaotic systems are distinguished by their sensitive dependence on
initial conditions. The absence of this property in quantum systems has lead to
a number of proposals for perturbation-based characterizations of quantum
chaos, including linear growth of entropy, exponential decay of fidelity, and
hypersensitivity to perturbation. All of these accurately predict chaos in the
classical limit, but it is not clear that they behave the same far from the
classical realm. We investigate the dynamics of a family of quantizations of
the baker's map, which range from a highly entangling unitary transformation to
an essentially trivial shift map. Linear entropy growth and fidelity decay are
exhibited by this entire family of maps, but hypersensitivity distinguishes
between the simple dynamics of the trivial shift map and the more complicated
dynamics of the other quantizations. This conclusion is supported by an
analytical argument for short times and numerical evidence at later times.
|
[
{
"version": "v1",
"created": "Tue, 13 Jun 2006 00:39:32 GMT"
},
{
"version": "v2",
"created": "Wed, 11 Oct 2006 03:42:06 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Scott",
"A. J.",
""
],
[
"Brun",
"Todd A.",
""
],
[
"Caves",
"Carlton M.",
""
],
[
"Schack",
"Ruediger",
""
]
] |
quant-ph/0606103
|
Damian Markham
|
Damian Markham, Janet Anders, Vlatko Vedral, Mio Murao and Akimasa
Miyake
|
Survival of entanglement in thermal states
|
6 pages, 2 figures. Changes made in line with publication
recommendations. Motivation and concequences of result clarified, with the
addition of one more example, which applies the result to give noise
thresholds for measurement based quantum computing. New author added with new
results
|
Euro. Phys. Lett. 81, 40006 (2008)
|
10.1209/0295-5075/81/40006
| null |
quant-ph
| null |
We present a general sufficiency condition for the presence of multipartite
entanglement in thermal states stemming from the ground state entanglement. The
condition is written in terms of the ground state entanglement and the
partition function and it gives transition temperatures below which
entanglement is guaranteed to survive. It is flexible and can be easily adapted
to consider entanglement for different splittings, as well as be weakened to
allow easier calculations by approximations. Examples where the condition is
calculated are given. These examples allow us to characterize a minimum gapping
behavior for the survival of entanglement in the thermodynamic limit. Further,
the same technique can be used to find noise thresholds in the generation of
useful resource states for one-way quantum computing.
|
[
{
"version": "v1",
"created": "Tue, 13 Jun 2006 01:59:31 GMT"
},
{
"version": "v2",
"created": "Tue, 12 Feb 2008 15:03:57 GMT"
}
] | 2008-02-13T00:00:00 |
[
[
"Markham",
"Damian",
""
],
[
"Anders",
"Janet",
""
],
[
"Vedral",
"Vlatko",
""
],
[
"Murao",
"Mio",
""
],
[
"Miyake",
"Akimasa",
""
]
] |
quant-ph/0606104
|
Russell Miller
|
A. D. Boozer, A. Boca, R. Miller, T. E. Northup, H. J. Kimble
|
Cooling to the Ground State of Axial Motion for One Atom Strongly
Coupled to an Optical Cavity
|
5 pages, 4 figures
| null |
10.1103/PhysRevLett.97.083602
| null |
quant-ph
| null |
Localization to the ground state of axial motion is demonstrated for a
single, trapped atom strongly coupled to the field of a high finesse optical
resonator. The axial atomic motion is cooled by way of coherent Raman
transitions on the red vibrational sideband. An efficient state detection
scheme enabled by strong coupling in cavity QED is used to record the Raman
spectrum, from which the state of atomic motion is inferred. We find that the
lowest vibrational level of the axial potential with zero-point energy 13uK is
occupied with probability P0~0.95.
|
[
{
"version": "v1",
"created": "Tue, 13 Jun 2006 03:13:54 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Boozer",
"A. D.",
""
],
[
"Boca",
"A.",
""
],
[
"Miller",
"R.",
""
],
[
"Northup",
"T. E.",
""
],
[
"Kimble",
"H. J.",
""
]
] |
quant-ph/0606105
|
Naoki Yamamoto
|
Naoki Yamamoto, Shinji Hara, Koji Tsumura
|
Suboptimal quantum-error-correcting procedure based on semidefinite
programming
|
6 pages, no figure, Some notations differ from those in the PRA
version
|
Physical Review A 71, 022322 (2005)
|
10.1103/PhysRevA.71.022322
| null |
quant-ph
| null |
In this paper, we consider a simplified error-correcting problem: for a fixed
encoding process, to find a cascade connected quantum channel such that the
worst fidelity between the input and the output becomes maximum. With the use
of the one-to-one parametrization of quantum channels, a procedure finding a
suboptimal error-correcting channel based on a semidefinite programming is
proposed. The effectiveness of our method is verified by an example of the
bit-flip channel decoding.
|
[
{
"version": "v1",
"created": "Tue, 13 Jun 2006 03:30:00 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Yamamoto",
"Naoki",
""
],
[
"Hara",
"Shinji",
""
],
[
"Tsumura",
"Koji",
""
]
] |
quant-ph/0606106
|
Naoki Yamamoto
|
Naoki Yamamoto, Maryam Fazel
|
Computational approach to quantum encoder design for purity optimization
|
13 pages, 1 figure
|
Physical Review A 76, 012327 (2007)
|
10.1103/PhysRevA.76.012327
| null |
quant-ph
| null |
In this paper, we address the problem of designing a quantum encoder that
maximizes the minimum output purity of a given decohering channel, where the
minimum is taken over all possible pure inputs. This problem is cast as a
max-min optimization problem with a rank constraint on an appropriately defined
matrix variable. The problem is computationally very hard because it is
non-convex with respect to both the objective function (output purity) and the
rank constraint. Despite this difficulty, we provide a tractable computational
algorithm that produces the exact optimal solution for codespace of dimension
two. Moreover, this algorithm is easily extended to cover the general class of
codespaces, in which case the solution is suboptimal in the sense that the
suboptimized output purity serves as a lower bound of the exact optimal purity.
The algorithm consists of a sequence of semidefinite programmings and can be
performed easily. Two typical quantum error channels are investigated to
illustrate the effectiveness of our method.
|
[
{
"version": "v1",
"created": "Tue, 13 Jun 2006 03:45:55 GMT"
},
{
"version": "v2",
"created": "Mon, 28 Aug 2006 09:45:34 GMT"
},
{
"version": "v3",
"created": "Fri, 27 Jul 2007 04:28:02 GMT"
}
] | 2011-11-09T00:00:00 |
[
[
"Yamamoto",
"Naoki",
""
],
[
"Fazel",
"Maryam",
""
]
] |
quant-ph/0606107
|
Marc Mezard
|
Lev Ioffe, Marc Mezard (LPTMS)
|
Asymmetric quantum error correcting codes
| null | null |
10.1103/PhysRevA.75.032345
| null |
quant-ph cond-mat.other
| null |
The noise in physical qubits is fundamentally asymmetric: in most devices,
phase errors are much more probable than bit flips. We propose a quantum error
correcting code which takes advantage of this asymmetry and shows good
performance at a relatively small cost in redundancy, requiring less than a
doubling of the number of physical qubits for error correction.
|
[
{
"version": "v1",
"created": "Tue, 13 Jun 2006 05:26:21 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Ioffe",
"Lev",
"",
"LPTMS"
],
[
"Mezard",
"Marc",
"",
"LPTMS"
]
] |
quant-ph/0606108
|
Guang Wu
|
Guang Wu, Jie Chen, Yao Li, and Heping Zeng
|
Stable polarization-encoded quantum key distribution in fiber
|
14 pages, 4 figures
| null | null | null |
quant-ph
| null |
Polarizations of single-photon pulses have been controlled with long-term
stability of more than 10 hours by using an active feedback technique for
auto-compensation of unpredictable polarization scrambling in long-distance
fiber. Experimental tests of long-term operations in 50, 75 and 100 km fibers
demonstrated that such a single-photon polarization control supported stable
polarization encoding in long-distance fibers to facilitate stable one-way
fiber system for polarization-encoded quantum key distribution, providing
quantum bit error rates below the absolute security threshold.
|
[
{
"version": "v1",
"created": "Tue, 13 Jun 2006 10:50:26 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Wu",
"Guang",
""
],
[
"Chen",
"Jie",
""
],
[
"Li",
"Yao",
""
],
[
"Zeng",
"Heping",
""
]
] |
quant-ph/0606109
|
Hyunseok Jeong
|
Hyunseok Jeong and Nguyen Ba An
|
GHZ-type and W-type entangled coherent states: generation and Bell-type
inequality tests without photon counting
|
8 pages, 5 figures, to be published in Phys. Rev. A
|
Phys. Rev. A 74, 022104 (2006)
|
10.1103/PhysRevA.74.022104
| null |
quant-ph
| null |
We study GHZ-type and W-type three-mode entangled coherent states. Both the
types of entangled coherent states violate Mermin's version of the Bell
inequality with threshold photon detection (i.e., without photon counting).
Such an experiment can be performed using linear optics elements and threshold
detectors with significant Bell violations for GHZ-type entangled coherent
states. However, to demonstrate Bell-type inequality violations for W-type
entangled coherent states, additional nonlinear interactions are needed. We
also propose an optical scheme to generate W-type entangled coherent states in
free-traveling optical fields. The required resources for the generation are a
single-photon source, a coherent state source, beam splitters, phase shifters,
photodetectors, and Kerr nonlinearities. Our scheme does not necessarily
require strong Kerr nonlinear interactions, i.e., weak nonlinearities can be
used for the generation of the W-type entangled coherent states. Furthermore,
it is also robust against inefficiencies of the single-photon source and the
photon detectors.
|
[
{
"version": "v1",
"created": "Tue, 13 Jun 2006 12:21:11 GMT"
},
{
"version": "v2",
"created": "Wed, 12 Jul 2006 07:12:47 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Jeong",
"Hyunseok",
""
],
[
"An",
"Nguyen Ba",
""
]
] |
quant-ph/0606110
|
Ho-Tsang Ng
|
H. T. Ng and K. Burnett
|
Entanglement between atomic condensates in an optical lattice: effects
of interaction range
|
5 pages, 3 figures, title changed
|
Phys. Rev. A 75, 023601 (2007)
|
10.1103/PhysRevA.75.023601
| null |
quant-ph cond-mat.stat-mech
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We study the area-dependent entropy and two-site entanglement for two state
Bose-Einstein condensates in a 2D optical lattice. We consider the case where
the array of two component condensates behave like an ensemble of spin-half
particles with the interaction to its nearest neighbors and next nearest
neighbors. We show how the Hamiltonian of their Bose-Einstein condensate
lattice with nearest-neighbor and next-nearest-neighbor interactions can be
mapped into a harmonic lattice. We use this to determine the entropy and
entanglement content of the lattice.
|
[
{
"version": "v1",
"created": "Tue, 13 Jun 2006 13:57:39 GMT"
},
{
"version": "v2",
"created": "Sun, 7 Aug 2011 11:20:21 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Ng",
"H. T.",
""
],
[
"Burnett",
"K.",
""
]
] |
quant-ph/0606111
|
Pedro Jesus Salas
|
Pedro J. Salas
|
Quality of a Quantum Error Correcting Scheme and Memory Error Threshold
Estimation
| null |
Quantum Information and Computation 6, No 6 (2006) 516-526
| null | null |
quant-ph
| null |
The error correcting capabilities of the Calderbank-Shor-Steane [[7,1,3]]
quantum code, together with a fault-tolerant syndrome extraction by means of
several ancilla states, have been numerically studied. A simple probability
expression to characterize the code ability for correcting an encoded qubit has
been considered. This probability, as a correction quality criterion, permits
the error correction capabilities among different recovery schemes to be
compared. The memory error threshold is calculated by means of the best method
of those considered.
|
[
{
"version": "v1",
"created": "Tue, 13 Jun 2006 14:25:21 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Salas",
"Pedro J.",
""
]
] |
quant-ph/0606112
|
Jaromir Fiurasek
|
Ladislav Mista Jr., Jaromir Fiurasek
|
Optimal partial estimation of quantum states from several copies
|
5 pages, 2 figures, RevTeX4
|
Phys. Rev. A 74, 022316 (2006).
|
10.1103/PhysRevA.74.022316
| null |
quant-ph
| null |
We derive analytical formula for the optimal trade-off between the mean
estimation fidelity and the mean fidelity of the qubit state after a partial
measurement on N identically prepared qubits. We also conjecture analytical
expression for the optimal fidelity trade-off in case of a partial measurement
on N identical copies of a d-level system.
|
[
{
"version": "v1",
"created": "Tue, 13 Jun 2006 16:01:42 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Mista",
"Ladislav",
"Jr."
],
[
"Fiurasek",
"Jaromir",
""
]
] |
quant-ph/0606113
|
Yevhen Miroshnychenko
|
Y. Miroshnychenko, W. Alt, I. Dotsenko, L. Foerster, M. Khudaverdyan,
D. Meschede, S. Reick, and A. Rauschenbeutel
|
Inserting two atoms into a single optical micropotential
|
4 pages, 4 figures
|
Phys. Rev. Lett. 97, 243003 (2006)
|
10.1103/PhysRevLett.97.243003
| null |
quant-ph
| null |
We recently demonstrated that strings of trapped atoms inside a standing wave
optical dipole trap can be rearranged using optical tweezers [Y. Miroshnychenko
et al., Nature, in press (2006)]. This technique allows us to actively set the
interatomic separations on the scale of the individual trapping potential
wells. Here, we use such a distance-control operation to insert two atoms into
the same potential well. The detected success rate of this manipulation is
16(+4/-3) %, in agreement with the predictions of a theoretical model based on
our independently determined experimental parameters.
|
[
{
"version": "v1",
"created": "Tue, 13 Jun 2006 16:17:02 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Miroshnychenko",
"Y.",
""
],
[
"Alt",
"W.",
""
],
[
"Dotsenko",
"I.",
""
],
[
"Foerster",
"L.",
""
],
[
"Khudaverdyan",
"M.",
""
],
[
"Meschede",
"D.",
""
],
[
"Reick",
"S.",
""
],
[
"Rauschenbeutel",
"A.",
""
]
] |
quant-ph/0606114
|
Louis H. Kauffman
|
Louis H. Kauffman and Samuel J. Lomonaco Jr
|
$q$ - Deformed Spin Networks, Knot Polynomials and Anyonic Topological
Quantum Computation
|
88 pages, 58 figures, LaTeX document
| null | null | null |
quant-ph
| null |
We review the q-deformed spin network approach to Topological Quantum Field
Theory and apply these methods to produce unitary representations of the braid
groups that are dense in the unitary groups. Our methods are rooted in the
bracket state sum model for the Jones polynomial. We give our results for a
large class of representations based on values for the bracket polynomial that
are roots of unity. We make a separate and self-contained study of the quantum
universal Fibonacci model in this framework. We apply our results to give
quantum algorithms for the computation of the colored Jones polynomials for
knots and links, and the Witten-Reshetikhin-Turaev invariant of three
manifolds.
|
[
{
"version": "v1",
"created": "Tue, 13 Jun 2006 17:39:56 GMT"
},
{
"version": "v2",
"created": "Tue, 20 Jun 2006 09:31:40 GMT"
},
{
"version": "v3",
"created": "Fri, 9 Feb 2007 07:42:10 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Kauffman",
"Louis H.",
""
],
[
"Lomonaco",
"Samuel J.",
"Jr"
]
] |
quant-ph/0606115
|
Poul S. Jessen
|
Greg A. Smith, Andrew Silberfarb, Ivan H. Deutsch, and Poul S. Jessen
|
Efficient Quantum State Estimation by Continuous Weak Measurement and
Dynamical Control
|
4 pages, 3 figures
| null |
10.1103/PhysRevLett.97.180403
| null |
quant-ph
| null |
We demonstrate a fast, robust and non-destructive protocol for quantum state
estimation based on continuous weak measurement in the presence of a controlled
dynamical evolution. Our experiment uses optically probed atomic spins as a
testbed, and successfully reconstructs a range of trial states with fidelities
of ~90%. The procedure holds promise as a practical diagnostic tool for the
study of complex quantum dynamics, the testing of quantum hardware, and as a
starting point for new types of quantum feedback control.
|
[
{
"version": "v1",
"created": "Tue, 13 Jun 2006 21:03:47 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Smith",
"Greg A.",
""
],
[
"Silberfarb",
"Andrew",
""
],
[
"Deutsch",
"Ivan H.",
""
],
[
"Jessen",
"Poul S.",
""
]
] |
quant-ph/0606116
|
Han Peng
|
Xin Li, Tian Liu, Han Peng, Hongtao Sun, Jiaqi Zhu
|
On Lower Bound of Worst Case Error Probability for Quantum
Fingerprinting with Shared Entanglement
| null | null | null | null |
quant-ph
| null |
This paper discusses properties of quantum fingerprinting with shared
entanglement. Under certain restriction of final measurement, a relation is
given between unitary operations of two parties. Then, by reducing to spherical
coding problem, this paper gives a lower bound of worst case error probability
for quantum fingerprinting with shared entanglement, showing a relation between
worst case error probability and the amount of entanglement(measured by Schmidt
number).
|
[
{
"version": "v1",
"created": "Wed, 14 Jun 2006 07:52:01 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Li",
"Xin",
""
],
[
"Liu",
"Tian",
""
],
[
"Peng",
"Han",
""
],
[
"Sun",
"Hongtao",
""
],
[
"Zhu",
"Jiaqi",
""
]
] |
quant-ph/0606117
|
Gyong Luck Khym
|
Gyong Luck Khym, Kicheon Kang
|
Charge Detection in a Closed-Loop Aharonov-Bohm Interferometer
|
4 pages with 4 figures
|
Phys.Rev. B74 (2006) 153309
|
10.1103/PhysRevB.74.153309
| null |
quant-ph astro-ph cond-mat.mes-hall
| null |
We report on a study of complementarity in a two-terminal "closed-loop"
Aharonov-Bohm interferometer. In this interferometer, the simple picture of
two-path interference cannot be applied. We introduce a nearby quantum point
contact to detect the electron in a quantum dot inserted in the interferometer.
We found that charge detection reduces but does not completely suppress the
interference even in the limit of perfect detection. We attribute this
phenomenon to the unique nature of the closed-loop interferometer. That is, the
closed-loop interferometer cannot be simply regarded as a two-path
interferometer because of multiple reflections of electrons. As a result, there
exist indistinguishable paths of the electron in the interferometer and the
interference survives even in the limit of perfect charge detection. This
implies that charge detection is not equivalent to path detection in a
closed-loop interferometer. We also discuss the phase rigidity of the
transmission probability for a two-terminal conductor in the presence of a
detector.
|
[
{
"version": "v1",
"created": "Wed, 14 Jun 2006 07:15:13 GMT"
},
{
"version": "v2",
"created": "Thu, 15 Jun 2006 06:59:09 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Khym",
"Gyong Luck",
""
],
[
"Kang",
"Kicheon",
""
]
] |
quant-ph/0606118
|
Zhe-Yu Jeff Ou
|
B. H. Liu, F. W. Sun, Y. X. Gong, Y. F. Huang, Z. Y. Ou, and G. C. Guo
|
Demonstration of Controllable Temporal Distinguishability in a
Three-Photon State
| null | null |
10.1209/0295-5075/77/24003
| null |
quant-ph
| null |
Multi-photon interference is at the heart of the recently proposed linear
optical quantum computing scheme and plays an essential role in many protocols
in quantum information. Indistinguishability is what leads to the effect of
quantum interference. Optical interferometers such as Michaelson interferometer
provide a measure for second-order coherence at one-photon level and
Hong-Ou-Mandel interferometer was widely employed to describe two-photon
entanglement and indistinguishability. However, there is not an effective way
for a system of more than two photons. Recently, a new interferometric scheme
was proposed to quantify the degree of multi-photon distinguishability. Here we
report an experiment to implement the scheme for three-photon case. We are able
to generate three photons with different degrees of temporal distinguishability
and demonstrate how to characterize them by the visibility of three-photon
interference. This method of quantitative description of multi-photon
indistinguishability will have practical implications in the implementation of
quantum information protocols.
|
[
{
"version": "v1",
"created": "Wed, 14 Jun 2006 08:13:50 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Liu",
"B. H.",
""
],
[
"Sun",
"F. W.",
""
],
[
"Gong",
"Y. X.",
""
],
[
"Huang",
"Y. F.",
""
],
[
"Ou",
"Z. Y.",
""
],
[
"Guo",
"G. C.",
""
]
] |
quant-ph/0606119
|
Bari\c{s} \"Oztop
|
Alexander A. Klyachko, Bar{\i}\c{s} \"Oztop, and Alexander S.
Shumovsky
|
Quantification of entanglement via uncertainties
|
Changed content, references added 7 pages, no figures, PRA in press
| null |
10.1103/PhysRevA.75.032315
| null |
quant-ph
| null |
We show that entanglement of pure multi-party states can be quantified by
means of quantum uncertainties of certain basic observables through the use of
measure that has been initially proposed in [10] for bipartite systems.
|
[
{
"version": "v1",
"created": "Wed, 14 Jun 2006 08:32:38 GMT"
},
{
"version": "v2",
"created": "Mon, 19 Feb 2007 11:54:56 GMT"
}
] | 2016-08-16T00:00:00 |
[
[
"Klyachko",
"Alexander A.",
""
],
[
"Öztop",
"Barış",
""
],
[
"Shumovsky",
"Alexander S.",
""
]
] |
quant-ph/0606120
|
Francesco Buscemi Dr
|
Francesco Buscemi, Giacomo Mauro D'Ariano, and Chiara Macchiavello
|
Economical realization of phase covariant devices in arbitrary
dimensions
|
18 pages, 1 fugure. This paper reviews and completes quant-ph/0407103
and quant-ph/0504016
|
J. Opt. Soc. Am. B 24, 363 (2007)
|
10.1364/JOSAB.24.000363
| null |
quant-ph
| null |
We describe a unified framework of phase covariant multi user quantum
transformations for d-dimensional quantum systems. We derive the optimal phase
covariant cloning and transposition tranformations for multi phase states. We
show that for some particular relations between the input and output number of
copies they correspond to economical tranformations, which can be achieved
without the need of auxiliary systems. We prove a relation between the optimal
phase covariant cloning and transposition maps, and optimal estimation of
multiple phases for equatorial states.
|
[
{
"version": "v1",
"created": "Wed, 14 Jun 2006 08:35:18 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Buscemi",
"Francesco",
""
],
[
"D'Ariano",
"Giacomo Mauro",
""
],
[
"Macchiavello",
"Chiara",
""
]
] |
quant-ph/0606121
|
Sepunaru Daniel
|
Daniel Sepunaru
|
On connection between classical and quantum mechanics
|
11 pages
| null | null | null |
quant-ph
| null |
We discuss an alternative version of non- relativistic Newtonian mechanics in
terms of a real Hilbert space mathematical framework. It is demonstrated that
the physics of this scheme correspondent with the standard formulation.
Heisenberg-Schrodinger non-relativistic quantum mechanics is considered
adequate and complete. Since the suggested theory is dispersion free, linear
superposition principle is not violated but cannot affect results of
measurements due to spectral decomposition theorem for self-adjoint operators
(the collapse of wave function).
|
[
{
"version": "v1",
"created": "Wed, 14 Jun 2006 13:29:25 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Sepunaru",
"Daniel",
""
]
] |
quant-ph/0606122
|
Andrei Khrennikov
|
Guillaume Adenier and Andrei Yu. Khrennikov
|
Is the Fair Sampling Assumption supported by EPR Experiments?
|
13 pages, 8 figures
|
J. Phys. B 40 No 1 (2007) 131-141
|
10.1088/0953-4075/40/1/012
| null |
quant-ph
| null |
We analyze optical EPR experimental data performed by Weihs et al in
Innsbruck 1997-1998. We show that for some linear combinations of the raw
coincidence rates, the experimental results display some anomalous behavior
that a more general source state (like non-maximally entangled state) cannot
straightforwardly account for. We attempt to explain these anomalies by taking
account of the relative efficiencies of the four channels. For this purpose, we
use the fair sampling assumption, and assume explicitly that the detection
efficiencies for the pairs of entangled photons can be written as a product of
the two corresponding detection efficiencies for the single photons. We show
that this explicit use of fair sampling cannot be maintained to be a reasonable
assumption as it leads to an apparent violation of the no-signalling principle.
|
[
{
"version": "v1",
"created": "Wed, 14 Jun 2006 15:37:20 GMT"
},
{
"version": "v2",
"created": "Tue, 14 Nov 2006 15:20:46 GMT"
}
] | 2007-09-08T00:00:00 |
[
[
"Adenier",
"Guillaume",
""
],
[
"Khrennikov",
"Andrei Yu.",
""
]
] |
quant-ph/0606123
|
Jose B. Almeida
|
Jose B. Almeida
|
The hidden geometric character of relativistic quantum mechanics
|
29 pages. Small changes in V3 suggested by referee
|
J. Math. Phys. 49(1), pp. 012301, (2007)
|
10.1063/1.2406055
| null |
quant-ph math-ph math.MP
| null |
The presentation makes use of geometric algebra, also known as Clifford
algebra, in 5-dimensional spacetime. The choice of this space is given the
character of first principle, justified solely by the consequences that can be
derived from such choice and their consistency with experimental results. Given
a metric space of any dimension, one can define monogenic functions, the
natural extension of analytic functions to higher dimensions; such functions
have null vector derivative and have previously been shown by other authors to
play a decisive role in lower dimensional spaces. All monogenic functions have
null Laplacian by consequence; in an hyperbolic space this fact leads
inevitably to a wave equation with plane-like solutions. This is also true for
5-dimensional spacetime and we will explore those solutions, establishing a
parallel with the solutions of the Dirac equation. For this purpose we will
invoke the isomorphism between the complex algebra of 4x4 matrices, also known
as Dirac's matrices. There is one problem with this isomorphism, because the
solutions to Dirac's equation are usually known as spinors (column matrices)
that don't belong to the 4x4 matrix algebra and as such are excluded from the
isomorphism. We will show that a solution in terms of Dirac spinors is
equivalent to a plane wave solution. Just as one finds in the standard
formulation, monogenic functions can be naturally split into positive/negative
energy together with left/right ones. This split is provided by geometric
projectors and we will show that there is a second set of projectors providing
an alternate 4-fold split. The possible implications of this alternate split
are not yet fully understood and are presently the subject of profound
research.
|
[
{
"version": "v1",
"created": "Wed, 14 Jun 2006 16:29:25 GMT"
},
{
"version": "v2",
"created": "Tue, 11 Jul 2006 10:25:58 GMT"
},
{
"version": "v3",
"created": "Thu, 11 Jan 2007 16:45:58 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Almeida",
"Jose B.",
""
]
] |
quant-ph/0606124
|
Gabriel Gustavo Carlo
|
Dario Poletti, Gabriel G. Carlo, Baowen Li
|
Current behavior of a quantum Hamiltonian ratchet in resonance
|
6 pages, 4 figures
| null |
10.1103/PhysRevE.75.011102
| null |
quant-ph cond-mat.soft
| null |
We investigate the ratchet current that appears in a kicked Hamiltonian
system when the period of the kicks corresponds to the regime of quantum
resonance. In the classical analogue, a spatial-temporal symmetry should be
broken to obtain a net directed current. It was recently discovered that in
quantum resonance the temporal symmetry can be kept, and we prove that breaking
the spatial symmetry is a necessary condition to find this effect.
Moreover, we show numerically and analytically how the direction of the
motion is dramatically influenced by the strength of the kicking potential and
the value of the period. By increasing the strength of the interaction this
direction changes periodically, providing us with a non-expected source of
current reversals in this quantum model. These reversals depend on the kicking
period also, though this behavior is theoretically more difficult to analyze.
Finally, we generalize the discussion to the case of a non-uniform initial
condition.
|
[
{
"version": "v1",
"created": "Wed, 14 Jun 2006 16:40:10 GMT"
},
{
"version": "v2",
"created": "Mon, 11 Dec 2006 10:46:29 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Poletti",
"Dario",
""
],
[
"Carlo",
"Gabriel G.",
""
],
[
"Li",
"Baowen",
""
]
] |
quant-ph/0606125
|
Scott Glancy
|
S. Glancy, E. Knill, and H. M. Vasconcelos
|
Entanglement Purification of Any Stabilizer State
|
11 pages, 0 figures, comments welcome, submitting to Physical Review
A
|
Phys. Rev. A 74, 032319 (2006)
|
10.1103/PhysRevA.74.032319
| null |
quant-ph
| null |
We present a method for multipartite entanglement purification of any
stabilizer state shared by several parties. In our protocol each party measures
the stabilizer operators of a quantum error-correcting code on his or her
qubits. The parties exchange their measurement results, detect or correct
errors, and decode the desired purified state. We give sufficient conditions on
the stabilizer codes that may be used in this procedure and find that Steane's
seven-qubit code is the smallest error-correcting code sufficient to purify any
stabilizer state. An error-detecting code that encodes two qubits in six can
also be used to purify any stabilizer state. We further specify which classes
of stabilizer codes can purify which classes of stabilizer states.
|
[
{
"version": "v1",
"created": "Wed, 14 Jun 2006 17:42:30 GMT"
}
] | 2012-05-18T00:00:00 |
[
[
"Glancy",
"S.",
""
],
[
"Knill",
"E.",
""
],
[
"Vasconcelos",
"H. M.",
""
]
] |
quant-ph/0606126
|
David Poulin
|
David Poulin
|
Optimal and Efficient Decoding of Concatenated Quantum Block Codes
|
Published version
|
Phys. Rev. A 74 052333 (2006)
|
10.1103/PhysRevA.74.052333
| null |
quant-ph
| null |
We consider the problem of optimally decoding a quantum error correction code
-- that is to find the optimal recovery procedure given the outcomes of partial
"check" measurements on the system. In general, this problem is NP-hard.
However, we demonstrate that for concatenated block codes, the optimal decoding
can be efficiently computed using a message passing algorithm. We compare the
performance of the message passing algorithm to that of the widespread
blockwise hard decoding technique. Our Monte Carlo results using the 5 qubit
and Steane's code on a depolarizing channel demonstrate significant advantages
of the message passing algorithms in two respects. 1) Optimal decoding
increases by as much as 94% the error threshold below which the error
correction procedure can be used to reliably send information over a noisy
channel. 2) For noise levels below these thresholds, the probability of error
after optimal decoding is suppressed at a significantly higher rate, leading to
a substantial reduction of the error correction overhead.
|
[
{
"version": "v1",
"created": "Wed, 14 Jun 2006 19:53:25 GMT"
},
{
"version": "v2",
"created": "Wed, 4 Apr 2007 19:41:32 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Poulin",
"David",
""
]
] |
quant-ph/0606127
|
Bartholomew Furrow
|
Bartholomew Furrow
|
A Panoply of Quantum Algorithms
|
32 pages. Presented at CIAR Quantum Information Processing meeting,
May 2006
| null | null | null |
quant-ph
| null |
We create a variety of new quantum algorithms that use Grover's algorithm and
similar techniques to give polynomial speedups over their classical
counterparts. We begin by introducing a set of tools that carefully minimize
the impact of errors on running time; those tools provide us with speedups to
already-published quantum algorithms, such as improving Durr, Heiligman, Hoyer
and Mhalla's algorithm for single-source shortest paths [quant-ph/0401091] by a
factor of lg N. The algorithms we construct from scratch have a range of
speedups, from O(E)->O(sqrt(VE lg V)) speedups in graph theory to an
O(N^3)->O(N^2) speedup in dynamic programming.
|
[
{
"version": "v1",
"created": "Thu, 15 Jun 2006 18:53:35 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Furrow",
"Bartholomew",
""
]
] |
quant-ph/0606128
|
Stephen D. Bartlett
|
Mark R. Dowling, Stephen D. Bartlett, Terry Rudolph, and Robert W.
Spekkens
|
How to observe a coherent superposition of an atom and a molecule
|
17 pages, 1 figure, comments welcome, published version (minor
changes)
|
Phys. Rev. A, 74, 052113 (2006)
|
10.1103/PhysRevA.74.052113
| null |
quant-ph cond-mat.other
| null |
We demonstrate that it is possible, in principle, to perform a Ramsey-type
interference experiment to exhibit a coherent superposition of a single atom
and a diatomic molecule. This gedanken experiment, based on the techniques of
Aharonov and Susskind [Phys. Rev. 155, 1428 (1967)], explicitly violates the
commonly-accepted superselection rule that forbids coherent superpositions of
eigenstates of differing atom number. This interference experiment makes use of
a Bose-Einstein condensate as a reference frame with which to perform the
coherent operations analogous to Ramsey pulses. We also investigate an
analogous gedanken experiment to exhibit a coherent superposition of a single
boson and a fermion, violating the commonly-accepted superselection rule
forbidding coherent superpositions of states of differing particle statistics;
in this case, the reference frame is realized by a multi-mode state of many
fermions. This latter case reproduces all of the relevant features of Ramsey
interferometry, including Ramsey fringes over many repetitions of the
experiment. However, the apparent inability of this proposed experiment to
produce well-defined relative phases between two distinct systems each
described by a coherent superposition of a boson and a fermion demonstrates
that there are additional, outstanding requirements to fully ``lift'' the
univalence superselection rule.
|
[
{
"version": "v1",
"created": "Thu, 15 Jun 2006 02:20:53 GMT"
},
{
"version": "v2",
"created": "Mon, 11 Dec 2006 13:32:25 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Dowling",
"Mark R.",
""
],
[
"Bartlett",
"Stephen D.",
""
],
[
"Rudolph",
"Terry",
""
],
[
"Spekkens",
"Robert W.",
""
]
] |
quant-ph/0606129
|
Alberto Ventura
|
F. Cannata, J.-P. Dedonder and A. Ventura
|
Scattering in PT-symmetric quantum mechanics
|
41 pages, to appear in Ann. Phys
|
Ann. Phys. 322 (2007) 397
|
10.1016/j.aop.2006.05.011
| null |
quant-ph
| null |
A general formalism is worked out for the description of one-dimensional
scattering in non-hermitian quantum mechanics and constraints on transmission
and reflection coefficients are derived in the cases of P, T, or PT invariance
of the Hamiltonian. Applications to some solvable PT-symmetric potentials are
shown in detail. Our main original results concern the association of
reflectionless potentials with asymptotic exact PT symmetry and the
peculiarities of separable kernels of non-local potentials in connection with
hermiticity, T invariance and PT invariance.
|
[
{
"version": "v1",
"created": "Thu, 15 Jun 2006 07:00:28 GMT"
},
{
"version": "v2",
"created": "Tue, 18 Jul 2006 06:31:04 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Cannata",
"F.",
""
],
[
"Dedonder",
"J. -P.",
""
],
[
"Ventura",
"A.",
""
]
] |
quant-ph/0606130
|
Marco Cozzini
|
P. Zanardi, M. Cozzini, and P. Giorda
|
Ground state fidelity and quantum phase transitions in free Fermi
systems
|
4 pages, 2 figures
| null |
10.1088/1742-5468/2007/02/L02002
| null |
quant-ph cond-mat.str-el
| null |
We compute the fidelity between the ground states of general quadratic
fermionic hamiltonians and analyze its connections with quantum phase
transitions. Each of these systems is characterized by a $L\times L$ real
matrix whose polar decomposition, into a non-negative $\Lambda$ and a unitary
$T$, contains all the relevant ground state (GS) information. The boundaries
between different regions in the GS phase diagram are given by the points of,
possibly asymptotic, singularity of $\Lambda$. This latter in turn implies a
critical drop of the fidelity function. We present general results as well as
their exemplification by a model of fermions on a totally connected graph.
|
[
{
"version": "v1",
"created": "Thu, 15 Jun 2006 09:10:42 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Zanardi",
"P.",
""
],
[
"Cozzini",
"M.",
""
],
[
"Giorda",
"P.",
""
]
] |
quant-ph/0606131
|
Aram Harrow
|
Aram W. Harrow and Andreas Winter
|
How many copies are needed for state discrimination?
|
1 page, submitted to QCMC'06, answer is O(log # of states)
|
IEEE Trans. Inf. Th., vol. 58, no. 1, pp. 1-2, Jan 2012
|
10.1109/TIT.2011.2169544
| null |
quant-ph
| null |
Given a collection of states (rho_1, ..., rho_N) with pairwise fidelities
F(rho_i, rho_j) <= F < 1, we show the existence of a POVM that, given
rho_i^{otimes n}, will identify i with probability >= 1-epsilon, as long as
n>=2(log N/eps)/log (1/F). This improves on previous results which were either
dimension-dependent or required that i be drawn from a known distribution.
|
[
{
"version": "v1",
"created": "Thu, 15 Jun 2006 11:33:53 GMT"
}
] | 2012-01-31T00:00:00 |
[
[
"Harrow",
"Aram W.",
""
],
[
"Winter",
"Andreas",
""
]
] |
quant-ph/0606132
|
Michael M. Wolf
|
Michael M. Wolf, David Perez-Garcia, Geza Giedke
|
Quantum Capacities of Bosonic Channels
|
5 pages, 2 figures
|
Phys. Rev. Lett. 98, 130501 (2007)
|
10.1103/PhysRevLett.98.130501
| null |
quant-ph
| null |
We investigate the capacity of bosonic quantum channels for the transmission
of quantum information. Achievable rates are determined from measurable moments
of the channel by showing that every channel can asymptotically simulate a
Gaussian channel which is characterized by second moments of the initial
channel. We calculate the quantum capacity for a class of Gaussian channels,
including channels describing optical fibers with photon losses, by proving
that Gaussian encodings are optimal. Along the way we provide a complete
characterization of degradable Gaussian channels and those arising from
teleportation protocols.
|
[
{
"version": "v1",
"created": "Thu, 15 Jun 2006 12:44:57 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Wolf",
"Michael M.",
""
],
[
"Perez-Garcia",
"David",
""
],
[
"Giedke",
"Geza",
""
]
] |
quant-ph/0606133
|
Shi-Jian Gu
|
Shi-Quan Su, Jun-Liang Song, and Shi-Jian Gu
|
Local entanglement and quantum phase transition in 1D transverse field
Ising model
|
5 pages, 5 figures
|
S. Q. Su, J. L. Song, and S. J. Gu, Phys. Rev. A 74, 032308 (2006)
|
10.1103/PhysRevA.74.032308
| null |
quant-ph
| null |
In this paper, we study the entanglement between two-neighboring sites and
the rest of the system in a simple quantum phase transition of 1D transverse
field Ising model. We find that the entanglement shows interesting scaling and
singular behavior around the critical point, and then can be use as a
convenient marker for the transition point.
|
[
{
"version": "v1",
"created": "Thu, 15 Jun 2006 15:38:24 GMT"
},
{
"version": "v2",
"created": "Fri, 29 Dec 2006 04:06:05 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Su",
"Shi-Quan",
""
],
[
"Song",
"Jun-Liang",
""
],
[
"Gu",
"Shi-Jian",
""
]
] |
quant-ph/0606134
|
Aurelian Isar
|
A. Isar, A. Sandulescu and W. Scheid
|
Purity and decoherence in the theory of a damped harmonic oscillator
|
24 pages
|
Phys. Rev. E, v. 60, p. 6371 (1999)
|
10.1103/PhysRevE.60.6371
| null |
quant-ph
| null |
For the generalized master equations derived by Karrlein and Grabert for the
microscopic model of a damped harmonic oscillator, the conditions for purity of
states are written, in particular for different initial conditions and
different types of damping, including Ohmic, Drude and weak coupling cases,
Agarwal and Weidlich-Haake models. It is shown that the states which remain
pure are the squeezed states with constant in time variances. For pure states,
the generalized nonlinear Schr\" odinger-type equations corresponding to these
master equations are also obtained. Then the condition for purity of states of
a damped harmonic oscillator is considered in the framework of Lindblad theory
for open quantum systems. For a special choice of the environment coefficients,
the correlated coherent states with constant variances and covariance are shown
to be the only states which remain pure all the time during the evolution of
the considered system. In Karrlein-Grabert and Lindblad models, as well as in
the considered particular models, the expressions of the rate of entropy
production is written and it is shown that the states which preserve their
purity in time are also the states which minimize the entropy production and,
therefore, they are the most stable ones under evolution in the presence of the
environment and play an important role in the description of decoherence
phenomenon.
|
[
{
"version": "v1",
"created": "Thu, 15 Jun 2006 16:44:35 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Isar",
"A.",
""
],
[
"Sandulescu",
"A.",
""
],
[
"Scheid",
"W.",
""
]
] |
quant-ph/0606135
|
Yury Sherkunov
|
Yury Sherkunov
|
Casimir-Polder interaction between an excited atom and a gas dielectric
medium
|
23 pages, 6 figures
|
PhysRevA 75, 012705 (2007)
|
10.1103/PhysRevA.75.012705
| null |
quant-ph
| null |
The Casimir-Polder potential for interaction between an excited atom and a
ground-state one in the retarded case obtained with the help of perturbation
technique drops as R^-2 with the distance between the atoms [E.A. Power,
T.Thirunamachandran, Phys. Rev. A, 47, 2539 (1993)]. It results in diverdent
integrals for interaction between an excited atom and a dilute gas medium. We
investigate interaction between two atoms embedded in a dielectric medium with
the help of non-perturbative approach. We take into account absorption of
photons in the medium. This approach solves the problem of divergence. We
consider interaction between an excited atom and a planar dielectric gas medium
of ground-state atoms. We show that the retarded interaction between an excited
atom and a gas of ground-state atoms is not oscillating but follows a simple
power law. We show that to obtain coventional non-retarded expression for the
van der Waals force between an excited atom and a dilute gas the distance
between the atom and the interface should be much smaller than the free mean
pass of a photon in the medium. Interaction between an excited atom and a
hemisphere of ground-state atoms is considered.
|
[
{
"version": "v1",
"created": "Thu, 15 Jun 2006 17:07:27 GMT"
},
{
"version": "v2",
"created": "Sun, 18 Jun 2006 07:18:15 GMT"
},
{
"version": "v3",
"created": "Mon, 9 Oct 2006 19:42:57 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Sherkunov",
"Yury",
""
]
] |
quant-ph/0606136
|
Du Jian-Zhong
|
Jian-Zhong Du, Su-Juan Qin, Qiao-Yan Wen, and Fu-Chen Zhu
|
Threshold quantum cryptograph based on Grover's algorithm
|
7 pages, 1 figures
| null |
10.1016/j.physleta.2006.11.024
| null |
quant-ph
| null |
Grover's operator in the two-qubit case can transform a basis into its
conjugated basis. A permutation operator can transform a state in the two
conjugated bases into its orthogonal state. These properties are included in a
threshold quantum protocol. The proposed threshold quantum protocol is secure
based the proof that the legitimate participators can only eavesdrop 2 bits of
3 bits operation information on one two-qubit with error probability 3/8. We
propose a scheme to detect the Trojan horse attack without destroying the legal
qubit.
|
[
{
"version": "v1",
"created": "Fri, 16 Jun 2006 06:02:11 GMT"
},
{
"version": "v2",
"created": "Tue, 27 Jun 2006 00:23:03 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Du",
"Jian-Zhong",
""
],
[
"Qin",
"Su-Juan",
""
],
[
"Wen",
"Qiao-Yan",
""
],
[
"Zhu",
"Fu-Chen",
""
]
] |
quant-ph/0606137
|
Annalisa Marzuoli
|
S. Garnerone, A. Marzuoli, M. Rasetti
|
Quantum Knitting
|
29 pages, 5 figures; to appear in Laser Journal
|
Laser Physics Vol. 16 No. 11 (2006) 1582-1594
|
10.1134/S1054660X06110120
| null |
quant-ph
| null |
We analyze the connections between the mathematical theory of knots and
quantum physics by addressing a number of algorithmic questions related to both
knots and braid groups.
Knots can be distinguished by means of `knot invariants', among which the
Jones polynomial plays a prominent role, since it can be associated with
observables in topological quantum field theory.
Although the problem of computing the Jones polynomial is intractable in the
framework of classical complexity theory, it has been recently recognized that
a quantum computer is capable of approximating it in an efficient way. The
quantum algorithms discussed here represent a breakthrough for quantum
computation, since approximating the Jones polynomial is actually a `universal
problem', namely the hardest problem that a quantum computer can efficiently
handle.
|
[
{
"version": "v1",
"created": "Fri, 16 Jun 2006 09:25:01 GMT"
}
] | 2007-06-13T00:00:00 |
[
[
"Garnerone",
"S.",
""
],
[
"Marzuoli",
"A.",
""
],
[
"Rasetti",
"M.",
""
]
] |
quant-ph/0606138
|
Antonio Acin
|
Antonio Acin, Nicolas Gisin, Benjamin Toner
|
Grothendieck's constant and local models for noisy entangled quantum
states
|
6 pages, 1 figure
|
Phys. Rev. A 73, 062105 (2006)
|
10.1103/PhysRevA.73.062105
| null |
quant-ph
| null |
We relate the nonlocal properties of noisy entangled states to Grothendieck's
constant, a mathematical constant appearing in Banach space theory. For
two-qubit Werner states $\rho^W_p=p \proj{\psi^-}+(1-p){\one}/{4}$, we show
that there is a local model for projective measurements if and only if $p \le
1/K_G(3)$, where $K_G(3)$ is Grothendieck's constant of order 3. Known bounds
on $K_G(3)$ prove the existence of this model at least for $p \lesssim 0.66$,
quite close to the current region of Bell violation, $p \sim 0.71$. We
generalize this result to arbitrary quantum states.
|
[
{
"version": "v1",
"created": "Fri, 16 Jun 2006 09:46:04 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Acin",
"Antonio",
""
],
[
"Gisin",
"Nicolas",
""
],
[
"Toner",
"Benjamin",
""
]
] |
quant-ph/0606139
|
Ruediger Schack
|
Christian D'Cruz, Tobias J. Osborne, Ruediger Schack (Royal Holloway,
University of London)
|
A Finite de Finetti Theorem for Infinite-Dimensional Systems
|
4 pages, 2 figures
|
Phys. Rev. Lett. 98, 160406 (2007)
|
10.1103/PhysRevLett.98.160406
| null |
quant-ph
| null |
We formulate and prove a de Finetti representation theorem for finitely
exchangeable states of a quantum system consisting of k infinite-dimensional
subsystems. The theorem is valid for states that can be written as the partial
trace of a pure state chosen from a family of subsets C_n of the full symmetric
subspace for $n$ subsystems. We show that such states become arbitrarily close
to mixtures of pure power states as n increases. We give a second equivalent
characterization of the family C_n.
|
[
{
"version": "v1",
"created": "Fri, 16 Jun 2006 13:06:33 GMT"
},
{
"version": "v2",
"created": "Wed, 26 Jul 2006 13:41:29 GMT"
},
{
"version": "v3",
"created": "Thu, 7 Dec 2006 18:03:20 GMT"
},
{
"version": "v4",
"created": "Thu, 8 Mar 2007 07:59:01 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"D'Cruz",
"Christian",
"",
"Royal Holloway,\n University of London"
],
[
"Osborne",
"Tobias J.",
"",
"Royal Holloway,\n University of London"
],
[
"Schack",
"Ruediger",
"",
"Royal Holloway,\n University of London"
]
] |
quant-ph/0606140
|
Barbara M. Terhal
|
Sergey Bravyi, David P. DiVincenzo, Roberto I. Oliveira and Barbara M.
Terhal
|
The Complexity of Stoquastic Local Hamiltonian Problems
|
21 pages Latex, 1 figure. v2 contains several small corrections. v3
has more small corrections
|
Quant. Inf. Comp. Vol.8, No.5, pp. 0361-0385 (2008)
| null | null |
quant-ph
| null |
We study the complexity of the Local Hamiltonian Problem (denoted as LH-MIN)
in the special case when a Hamiltonian obeys conditions of the Perron-Frobenius
theorem: all off-diagonal matrix elements in the standard basis are real and
non-positive. We will call such Hamiltonians, which are common in the natural
world, stoquastic. An equivalent characterization of stoquastic Hamiltonians is
that they have an entry-wise non-negative Gibbs density matrix for any
temperature. We prove that LH-MIN for stoquastic Hamiltonians belongs to the
complexity class AM -- a probabilistic version of NP with two rounds of
communication between the prover and the verifier. We also show that 2-local
stoquastic LH-MIN is hard for the class MA. With the additional promise of
having a polynomial spectral gap, we show that stoquastic LH-MIN belongs to the
class POSTBPP=BPPpath -- a generalization of BPP in which a post-selective
readout is allowed. This last result also shows that any problem solved by
adiabatic quantum computation using stoquastic Hamiltonians lies in PostBPP.
|
[
{
"version": "v1",
"created": "Fri, 16 Jun 2006 19:36:58 GMT"
},
{
"version": "v2",
"created": "Mon, 17 Jul 2006 18:03:24 GMT"
},
{
"version": "v3",
"created": "Mon, 17 Jul 2006 21:49:15 GMT"
},
{
"version": "v4",
"created": "Tue, 2 Oct 2007 17:22:07 GMT"
}
] | 2009-03-25T00:00:00 |
[
[
"Bravyi",
"Sergey",
""
],
[
"DiVincenzo",
"David P.",
""
],
[
"Oliveira",
"Roberto I.",
""
],
[
"Terhal",
"Barbara M.",
""
]
] |
quant-ph/0606141
|
Thomas Marcella Dr
|
Thomas V Marcella
|
An axiomatic approach to Einstein's boxes
|
14 pages, submitted to American Journal of Physics
| null | null | null |
quant-ph
| null |
The fallacies inherent in the Einstein's Boxes thought experiment are made
evident by taking an axiomatic approach to quantum mechanics while ignoring
notions not supported by the postulates or by experimental observation. We
emphasize that the postulates contain everything needed to completely describe
a quantum experiment. We discuss the non-classical nature of both the state
vector and the experiment that it represents. Einstein's Boxes is then
described by the formalism alone. We see that it is no different from any other
experiment in which a two-state observable is measured.
|
[
{
"version": "v1",
"created": "Sat, 17 Jun 2006 01:15:06 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Marcella",
"Thomas V",
""
]
] |
quant-ph/0606142
|
Kartik Srinivasan
|
Kartik Srinivasan and Oskar Painter
|
Mode Coupling and Cavity-Quantum-Dot Interactions in a Fiber-Coupled
Microdisk Cavity
|
rev4: updated references and added additional correlation function
calculations; to appear in Phys. Rev. A in Feb 2007
|
Phys. Rev. A., v75, art. no. 023814, Feb. 23, 2007
|
10.1103/PhysRevA.75.023814
| null |
quant-ph
| null |
A quantum master equation model for the interaction between a two-level
system and whispering-gallery modes (WGMs) of a microdisk cavity is presented,
with specific attention paid to current experiments involving a semiconductor
quantum dot (QD) embedded in a fiber-coupled, AlGaAs microdisk cavity. In
standard single mode cavity QED, three important rates characterize the system:
the QD-cavity coupling rate g, the cavity decay rate kappa, and the QD
dephasing rate gamma_perpendicular. A more accurate model of the microdisk
cavity includes two additional features. The first is a second cavity mode that
can couple to the QD, which for an ideal microdisk corresponds to a traveling
wave WGM propagating counter to the first WGM. The second feature is a coupling
between these two traveling wave WGMs, at a rate beta, due to backscattering
caused by surface roughness that is present in fabricated devices. We consider
the transmitted and reflected signals from the cavity for different parameter
regimes of {g,beta,kappa,gamma_perpendicular}. A result of this analysis is
that even in the presence of negligible roughness induced backscattering, a
strongly coupled QD mediates coupling between the traveling wave WGMs,
resulting in an enhanced effective coherent coupling rate g = sqrt(2)*g0
corresponding to that of a standing wave WGM with an electric field maximum at
the position of the QD. In addition, analysis of the second-order correlation
function of the reflected signal from the cavity indicates that regions of
strong photon antibunching or bunching may be present depending upon the
strength of coupling of the QD to each of the cavity modes. Such intensity
correlation information will likely be valuable in interpreting experimental
measurements of a strongly-coupled QD to a bi-modal WGM cavity.
|
[
{
"version": "v1",
"created": "Sat, 17 Jun 2006 17:30:43 GMT"
},
{
"version": "v2",
"created": "Fri, 23 Jun 2006 02:48:02 GMT"
},
{
"version": "v3",
"created": "Thu, 14 Sep 2006 17:35:51 GMT"
},
{
"version": "v4",
"created": "Fri, 26 Jan 2007 03:14:34 GMT"
}
] | 2013-05-29T00:00:00 |
[
[
"Srinivasan",
"Kartik",
""
],
[
"Painter",
"Oskar",
""
]
] |
quant-ph/0606143
|
George Jaroszkiewicz
|
George Jaroszkiewicz and Jon Eakins
|
Bohr-Heisenberg Reality and System-Free Quantum Mechanics
|
10 pages, submitted to Proceedings of Foundations of Probability and
Physics -4, June 4-9, 2006, Vaxjo, Sweden
| null |
10.1063/1.2713452
| null |
quant-ph
| null |
Motivated by Heisenberg's assertion that electron trajectories do not exist
until they are observed, we present a new approach to quantum mechanics in
which the concept of observer independent system under observation is
eliminated. Instead, the focus is only on observers and apparatus, the former
describing the latter in terms of labstates. These are quantum states over
time-dependent Heisenberg nets, which are quantum registers of qubits
representing information gateways accessible to the observers. We discuss the
motivation for this approach and lay down the basic principles and mathematical
notation.
|
[
{
"version": "v1",
"created": "Mon, 19 Jun 2006 10:55:49 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Jaroszkiewicz",
"George",
""
],
[
"Eakins",
"Jon",
""
]
] |
quant-ph/0606144
|
Hing Tong Cho
|
Hing-Tong Cho and Choon-Lin Ho
|
A Novel Quasi-Exactly Solvable Model with Total Transmission Modes
|
Revtex, 9 pages, 1 eps figure, claim on continuous bound state
spectra removed, more discussions on self-adjoint extensions added
| null | null | null |
quant-ph hep-th
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
In this paper we present a novel quasi-exactly solvable model with symmetric
inverted potentials which are unbounded from below. The quasi-exactly solvable
states are shown to be total transmission (or reflectionless) modes. From these
modes even and odd wavefunctions can be constructed which are normalizable and
flux-zero. Under the procedure of self-adjoint extension, a discrete spectrum
of bound states can be obtained for these inverted potentials and the solvable
part of the spectrum is the quasi-exactly solvable states we have discovered.
|
[
{
"version": "v1",
"created": "Sun, 18 Jun 2006 06:09:10 GMT"
},
{
"version": "v2",
"created": "Fri, 15 Jun 2007 03:28:30 GMT"
},
{
"version": "v3",
"created": "Wed, 30 Jan 2008 09:01:17 GMT"
},
{
"version": "v4",
"created": "Tue, 10 Jun 2008 06:33:33 GMT"
}
] | 2008-06-10T00:00:00 |
[
[
"Cho",
"Hing-Tong",
""
],
[
"Ho",
"Choon-Lin",
""
]
] |
quant-ph/0606145
|
R. Arun
|
R. Arun, Offir Cohen, and I.Sh. Averbukh
|
Atom Lithography with Near-Resonant Light Masks: Quantum Optimization
Analysis
|
10 pages including 11 figures in Revtex
| null |
10.1103/PhysRevA.81.063809
| null |
quant-ph
| null |
We study the optimal focusing of two-level atoms with a near resonant
standing wave light, using both classical and quantum treatments of the
problem. Operation of the focusing setup is considered as a nonlinear spatial
squeezing of atoms in the thin- and thick-lens regimes. It is found that the
near-resonant standing wave focuses the atoms with a reduced background in
comparison with far-detuned light fields. For some parameters, the quantum
atomic distribution shows even better localization than the classical one.
Spontaneous emission effects are included via the technique of quantum Monte
Carlo wave function simulations. We investigate the extent to which
non-adiabatic and spontaneous emission effects limit the achievable minimal
size of the deposited structures.
|
[
{
"version": "v1",
"created": "Sun, 18 Jun 2006 12:55:40 GMT"
}
] | 2015-07-15T00:00:00 |
[
[
"Arun",
"R.",
""
],
[
"Cohen",
"Offir",
""
],
[
"Averbukh",
"I. Sh.",
""
]
] |
quant-ph/0606146
|
Kamil Br\'adler
|
Kamil Bradler and Rocio Jauregui
|
Entanglement enhancement and postselection for two atoms interacting
with thermal light
|
accepted for publication in J. Phys. B
| null |
10.1088/0953-4075/40/4/009
| null |
quant-ph
| null |
The evolution of entanglement for two identical two-level atoms coupled to a
resonant thermal field is studied for two different families of input states.
Entanglement enhancement is predicted for a well defined region of the
parameter space of one of these families. The most intriguing result is the
possibility of probabilistic production of maximally entangled atomic states
even if the input atomic state is factorized and the corresponding output state
is separable.
|
[
{
"version": "v1",
"created": "Mon, 19 Jun 2006 18:26:30 GMT"
},
{
"version": "v2",
"created": "Tue, 17 Oct 2006 00:43:12 GMT"
},
{
"version": "v3",
"created": "Mon, 22 Jan 2007 17:58:27 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Bradler",
"Kamil",
""
],
[
"Jauregui",
"Rocio",
""
]
] |
quant-ph/0606147
|
Denis Boiron
|
Jose Viana Gomes (LCFIO), Aur\'elien Perrin (LCFIO), Martijn
Schellekens (LCFIO), Denis Boiron (LCFIO), Christoph I. Westbrook (LCFIO),
Michael Belsley
|
Theory for a Hanbury Brown Twiss experiment with a ballistically
expanding cloud of cold atoms
| null |
Physical Review A 74 (07/11/2006) 053607
|
10.1103/PhysRevA.74.053607
| null |
quant-ph cond-mat.other
| null |
We have studied one-body and two-body correlation functions in a
ballistically expanding, non-interacting atomic cloud in the presence of
gravity. We find that the correlation functions are equivalent to those at
thermal equilibrium in the trap with an appropriate rescaling of the
coordinates. We derive simple expressions for the correlation lengths and give
some physical interpretations. Finally a simple model to take into account
finite detector resolution is discussed.
|
[
{
"version": "v1",
"created": "Mon, 19 Jun 2006 17:23:05 GMT"
},
{
"version": "v2",
"created": "Thu, 30 Nov 2006 22:32:35 GMT"
}
] | 2016-08-16T00:00:00 |
[
[
"Gomes",
"Jose Viana",
"",
"LCFIO"
],
[
"Perrin",
"Aurélien",
"",
"LCFIO"
],
[
"Schellekens",
"Martijn",
"",
"LCFIO"
],
[
"Boiron",
"Denis",
"",
"LCFIO"
],
[
"Westbrook",
"Christoph I.",
"",
"LCFIO"
],
[
"Belsley",
"Michael",
""
]
] |
quant-ph/0606148
|
Shao-Ming Fei
|
Bao-Zhi Sun, Shao-Ming Fei
|
Invariants for a Class of Nongeneric Three-qubit States
|
7 pages
|
Commun. Theor. Phys. 45(2006)1007-1010
|
10.1088/0253-6102/45/6/010
| null |
quant-ph
| null |
We investigate the equivalence of quantum states under local unitary
transformations. A complete set of invariants under local unitary
transformations is presented for a class of non-generic three-qubit mixed
states. It is shown that two such states in this class are locally equivalent
if and only if all these invariants have equal values for them.
|
[
{
"version": "v1",
"created": "Mon, 19 Jun 2006 03:16:49 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Sun",
"Bao-Zhi",
""
],
[
"Fei",
"Shao-Ming",
""
]
] |
quant-ph/0606149
|
Vlatko Vedral
|
M. O. Terra Cunha, J. A. Dunningham, and V. Vedral
|
Entanglement in single particle systems
|
6 pages, 1 figure
| null | null | null |
quant-ph
| null |
We address some of the most commonly raised questions about entanglement,
especially with regard to so-called occupation number entanglement. To answer
unambiguously whether entanglement can exist in a one-atom delocalized state,
we propose an experiment capable of showing violations of Bell's inequality
using only this state and local operations. As a byproduct, this experiment
suggests a means of creating an entangled state of two different chemical
species. By comparison with a massless system, we argue that there should be no
fundamental objection to such a superposition and its creation may be within
reach of present technology.
|
[
{
"version": "v1",
"created": "Mon, 19 Jun 2006 03:19:27 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Cunha",
"M. O. Terra",
""
],
[
"Dunningham",
"J. A.",
""
],
[
"Vedral",
"V.",
""
]
] |
quant-ph/0606150
|
Safa Jami
|
Safa Jami
|
Noisy Teleportation
| null | null | null | null |
quant-ph
| null |
Entanglement is a key resource in many quantum information applications. One
of these applications is quantum teleportation.The purpose of teleportation is
sending qubits across quantum channels. In general these quantum channels are
noisy and therefore limit the fidelity of transmission.In this paper we
consider the effect of noise on teleportation and finally find the fidelity of
teleportation in presence of noise.
|
[
{
"version": "v1",
"created": "Mon, 19 Jun 2006 06:58:44 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Jami",
"Safa",
""
]
] |
quant-ph/0606151
|
Joerg Evers
|
M. Macovei, J. Evers, G.-x. Li and C. H. Keitel
|
Strong-field spatial interference in a tailored electromagnetic bath
|
final version
|
Phys. Rev. Lett. 98, 043602 (2007)
|
10.1103/PhysRevLett.98.043602
| null |
quant-ph
| null |
Light scattered by a regular structure of atoms can exhibit interference
signatures, similar to the classical double-slit. These first-order
interferences, however, vanish for strong light intensities, restricting
potential applications. Here, we show how to overcome these limitations to
quantum interference in strong fields. First, we recover the first-order
interference in strong fields via a tailored electromagnetic bath with a
suitable frequency dependence. At strong driving, the optical properties for
different spectral bands are distinct, thus extending the set of observables.
We further show that for a two-photon detector as, e.g., in lithography,
increasing the field intensity leads to twice the spatial resolution of the
second-order interference pattern compared to the weak-field case.
|
[
{
"version": "v1",
"created": "Mon, 19 Jun 2006 08:12:24 GMT"
},
{
"version": "v2",
"created": "Thu, 1 Feb 2007 10:55:07 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Macovei",
"M.",
""
],
[
"Evers",
"J.",
""
],
[
"Li",
"G. -x.",
""
],
[
"Keitel",
"C. H.",
""
]
] |
quant-ph/0606152
|
Zhangqi Yin
|
Zhang-qi Yin and Fu-li Li
|
Multiatom and resonant interaction scheme for quantum state transfer and
logical gates between two remote cavities via an optical fiber
|
24 pages, 8 figures; Corrected typos in fig6(b),(c) and references;
Adding disscussion on experimental feasibility in the last section. Accepted
for PRA
|
Phys. Rev. A 75, 012324 (2007)
|
10.1103/PhysRevA.75.012324
| null |
quant-ph
| null |
A system consisting of two single-mode cavities spatially separated and
connected by an optical fiber and multiple two-level atoms trapped in the
cavities is considered. If the atoms resonantly and collectively interact with
the local cavity fields but there is no direct interaction between the atoms,
we show that an ideal quantum state transfer and highly reliable quantum swap,
entangling, and controlled-Z gates can be deterministically realized between
the distant cavities. We find that the operation of state transfer and swap,
entangling, and controlled-Z gates can be greatly speeded up as number of the
atoms in the cavities increases. We also notice that the effects of spontaneous
emission of atoms and photon leakage out of cavity on the quantum processes can
also be greatly diminished in the multiatom case.
|
[
{
"version": "v1",
"created": "Mon, 19 Jun 2006 09:58:40 GMT"
},
{
"version": "v2",
"created": "Thu, 22 Jun 2006 14:36:52 GMT"
},
{
"version": "v3",
"created": "Wed, 29 Nov 2006 10:24:54 GMT"
},
{
"version": "v4",
"created": "Thu, 25 Jan 2007 01:57:22 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Yin",
"Zhang-qi",
""
],
[
"Li",
"Fu-li",
""
]
] |
quant-ph/0606153
|
Hyunseok Jeong
|
Hyunseok Jeong, Andrew M. Lance, Nicolai B. Grosse, Thomas Symul, Ping
Koy Lam, and Timothy C. Ralph
|
Conditional quantum-state engineering using ancillary squeezed-vacuum
states
|
10 pages, 14 figures, use pdf version, high quality figures available
on request
|
Phys. Rev. A 74, 033813 (2006)
|
10.1103/PhysRevA.74.033813
| null |
quant-ph
| null |
We investigate an optical scheme to conditionally engineer quantum states
using a beam splitter, homodyne detection and a squeezed vacuum as an ancillar
state. This scheme is efficient in producing non-Gaussian quantum states such
as squeezed single photons and superpositions of coherent states (SCSs). We
show that a SCS with well defined parity and high fidelity can be generated
from a Fock state of $n\leq4$, and conjecture that this can be generalized for
an arbitrary $n$ Fock state. We describe our experimental demonstration of this
scheme using coherent input states and measuring experimental fidelities that
are only achievable using quantum resources.
|
[
{
"version": "v1",
"created": "Mon, 19 Jun 2006 14:33:55 GMT"
},
{
"version": "v2",
"created": "Tue, 26 Sep 2006 02:43:10 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Jeong",
"Hyunseok",
""
],
[
"Lance",
"Andrew M.",
""
],
[
"Grosse",
"Nicolai B.",
""
],
[
"Symul",
"Thomas",
""
],
[
"Lam",
"Ping Koy",
""
],
[
"Ralph",
"Timothy C.",
""
]
] |
quant-ph/0606154
|
Mark Hillery
|
Mark Hillery and M. Suhail Zubairy
|
Entanglement conditions for two-mode states: Applications
|
7 pages, no figures, replaced with published version
|
Phys. Rev. A 74, 032333 (2006)
|
10.1103/PhysRevA.74.032333
| null |
quant-ph
| null |
We examine the implications of several recently derived conditions [Hillery
and Zubairy, Phys. Rev. Lett. 96, 050503 (2006)] for determining when a
two-mode state is entangled. We first find examples of non-Gaussian states that
satisfy these conditions. We then apply the entanglement conditions to the
study of several linear devices, the beam splitter, the parametric amplifier,
and the linear phase-insensitive amplifier. For the first two, we find
conditions on the input states that guarantee that the output states are
entangled. For the linear amplifier, we determine in the limit of high and no
gain, when an entangled input leads to an entangled output. Finally, we show
how application of two two-mode entanglement conditions to a three-mode state
can serve as a test of genuine three-mode entanglement.
|
[
{
"version": "v1",
"created": "Mon, 19 Jun 2006 12:41:53 GMT"
},
{
"version": "v2",
"created": "Mon, 2 Oct 2006 13:48:53 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Hillery",
"Mark",
""
],
[
"Zubairy",
"M. Suhail",
""
]
] |
quant-ph/0606155
|
Alexey Kalachev
|
Alexey Kalachev, Stefan Kroll
|
Coherent control of collective spontaneous emission in an extended
atomic ensemble and quantum storage
|
11 pages, 4 figures, submitted to PRA
| null |
10.1103/PhysRevA.74.023814
| null |
quant-ph
| null |
Coherent control of collective spontaneous emission in an extended atomic
ensemble resonantly interacting with single-photon wave packets is analyzed. A
scheme for coherent manipulation of collective atomic states is developed such
that superradiant states of the atomic system can be converted into subradiant
ones and vice versa. Possible applications of such a scheme for optical quantum
state storage and single-photon wave packet shaping are discussed. It is shown
that also in the absence of inhomogeneous broadening of the resonant line,
single-photon wave packets with arbitrary pulse shape may be recorded as a
subradiant state and reconstructed even although the duration of the wave
packets is larger than the superradiant life-time. Specifically the
applicability for storing time-bin qubits, which are used in quantum
cryptography is analyzed.
|
[
{
"version": "v1",
"created": "Mon, 19 Jun 2006 15:25:49 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Kalachev",
"Alexey",
""
],
[
"Kroll",
"Stefan",
""
]
] |
quant-ph/0606156
|
Jaromir Fiurasek
|
Jaromir Fiurasek
|
Optimal probabilistic estimation of quantum states
|
7 pages, 2 figures, ReVTeX4
|
New J. Phys. 8, 192 (2006).
|
10.1088/1367-2630/8/9/192
| null |
quant-ph
| null |
We extend the concept of probabilistic unambiguous discrimination of quantum
states to quantum state estimation. We consider a scenario where the
measurement device can output either an estimate of the unknown input state or
an inconclusive result. We present a general method how to evaluate the maximum
fidelity achievable by the probabilistic estimation strategy. We illustrate our
method on two explicit examples: estimation of a qudit from a pair of conjugate
qudits and phase covariant estimation of a qubit from N copies. We show that by
allowing for inconclusive results it is possible to reach estimation fidelity
higher than that achievable by the best deterministic estimation strategy.
|
[
{
"version": "v1",
"created": "Mon, 19 Jun 2006 16:23:25 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Fiurasek",
"Jaromir",
""
]
] |
quant-ph/0606157
|
Yaakov S. Weinstein
|
Yaakov S. Weinstein, C. Stephen Hellberg
|
A Scalable Architecture for Coherence-Preserving Qubits
|
4 pages, 4 figures
|
Phys. Rev. Lett. 98, 110501 (2007).
|
10.1103/PhysRevLett.98.110501
| null |
quant-ph
| null |
We propose scalable architectures for the coherence-preserving qubits
introduced by Bacon, Brown, and Whaley [Phys. Rev. Lett. {\bf 87}, 247902
(2001)]. These architectures employ extra qubits providing additional degrees
of freedom to the system. We show that these extra degrees of freedom can be
used to counter errors in coupling strength within the coherence-preserving
qubit and to combat interactions with environmental qubits. The presented
architectures incorporate experimentally viable methods for inter-logical-qubit
coupling and can implement a controlled phase gate via three simultaneous
Heisenberg exchange operations. The extra qubits also provide flexibility in
the arrangement of the physical qubits. Specifically, all physical qubits of a
coherent-preserving qubit lattice can be placed in two spatial dimensions. Such
an arrangement allows for universal cluster state computation.
|
[
{
"version": "v1",
"created": "Mon, 19 Jun 2006 17:13:45 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Weinstein",
"Yaakov S.",
""
],
[
"Hellberg",
"C. Stephen",
""
]
] |
quant-ph/0606158
|
Lin Tian
|
L. Tian
|
Correcting low-frequency noise with continuous measurement
|
10 pages, 3 figures, submitted
|
Phys. Rev. Lett. 98, 153602 (2007)
|
10.1103/PhysRevLett.98.153602
| null |
quant-ph cond-mat.mes-hall
| null |
Low-frequency noise presents a serious source of decoherence in solid-state
qubits. When combined with a continuous weak measurement of the eigenstates,
the low-frequency noise induces a second-order relaxation between the qubit
states. Here we show that the relaxation provides a unique approach to
calibrate the low-frequency noise in the time-domain. By encoding one qubit
with two physical qubits that are alternatively calibrated, quantum logic gates
with high fidelity can be performed.
|
[
{
"version": "v1",
"created": "Mon, 19 Jun 2006 20:36:18 GMT"
}
] | 2011-07-26T00:00:00 |
[
[
"Tian",
"L.",
""
]
] |
quant-ph/0606159
|
Dimitris G. Angelakis
|
Dimitris G. Angelakis, Marcelo F. Santos, Sougato Bose
|
Photon blockade induced Mott transitions and XY spin models in coupled
cavity arrays
|
4 pages, 3 figures
|
Phys. Rev. A (Rap. Com.) 76, 031805 (2007)
|
10.1103/PhysRevA.76.031805
| null |
quant-ph
| null |
As photons do not interact with each other, it is interesting to ask whether
photonic systems can be modified to exhibit the phases characteristic of
strongly coupled many-body systems. We demonstrate how a Mott insulator type of
phase of excitations can arise in an array of coupled electromagnetic cavities,
each of which is coupled resonantly to a {\em single} two level system
(atom/quantum dot/Cooper pair) and can be individually addressed from outside.
In the Mott phase each atom-cavity system has the same integral number of net
polaritonic (atomic plus photonic) excitations with photon blockade providing
the required repulsion between the excitations in each site. Detuning the
atomic and photonic frequencies suppresses this effect and induces a transition
to a photonic superfluid. We also show that for zero detuning, the system can
simulate the dynamics of many body spin systems.
|
[
{
"version": "v1",
"created": "Tue, 20 Jun 2006 19:47:48 GMT"
},
{
"version": "v2",
"created": "Thu, 18 Jan 2007 20:14:00 GMT"
},
{
"version": "v3",
"created": "Tue, 17 Jul 2007 14:53:56 GMT"
}
] | 2007-09-30T00:00:00 |
[
[
"Angelakis",
"Dimitris G.",
""
],
[
"Santos",
"Marcelo F.",
""
],
[
"Bose",
"Sougato",
""
]
] |
quant-ph/0606160
|
Feng Shuang
|
Feng Shuang, Herschel Rabitz
|
Cooperating or Fighting with Decoherence in the Optimal Control of
Quantum Dynamics
| null |
Journal of Chemical Physics 124, 154105 (2006)
|
10.1063/1.2186644
| null |
quant-ph
| null |
This paper explores the use of laboratory closed-loop learning control to
either fight or cooperate with decoherence in the optimal manipulation of
quantum dynamics. Simulations of the processes are performed in a Lindblad
formulation on multilevel quantum systems strongly interacting with the
environment without spontaneous emission. When seeking a high control yield it
is possible to find fields that successfully fight with decoherence while
attaining a good quality yield. When seeking modest control yields, fields can
be found which are optimally shaped to cooperate with decoherence and thereby
drive the dynamics more efficiently. In the latter regime when the control
field and the decoherence strength are both weak, a theoretical foundation is
established to describe how they cooperate with each other. In general, the
results indicate that the population transfer objectives can be effectively met
by appropriately either fighting or cooperating with decoherence.
|
[
{
"version": "v1",
"created": "Tue, 20 Jun 2006 04:14:55 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Shuang",
"Feng",
""
],
[
"Rabitz",
"Herschel",
""
]
] |
quant-ph/0606161
|
Richard Cleve
|
Christoph Dankert, Richard Cleve, Joseph Emerson, Etera Livine
|
Exact and Approximate Unitary 2-Designs: Constructions and Applications
|
7 pages, updating to version published in 2009
|
Physical Review A 80, 012304 (2009)
|
10.1103/PhysRevA.80.012304
| null |
quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We develop the concept of a unitary t-design as a means of expressing
operationally useful subsets of the stochastic properties of the uniform (Haar)
measure on the unitary group U(2^n) on n qubits. In particular, sets of
unitaries forming 2-designs have wide applicability to quantum information
protocols. We devise an O(n)-size in-place circuit construction for an
approximate unitary 2-design. We then show that this can be used to construct
an efficient protocol for experimentally characterizing the fidelity of a
quantum process on n qubits with quantum circuits of size O(n) without
requiring any ancilla qubits, thereby improving upon previous approaches.
|
[
{
"version": "v1",
"created": "Tue, 20 Jun 2006 05:11:22 GMT"
},
{
"version": "v2",
"created": "Fri, 31 Aug 2012 20:26:07 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Dankert",
"Christoph",
""
],
[
"Cleve",
"Richard",
""
],
[
"Emerson",
"Joseph",
""
],
[
"Livine",
"Etera",
""
]
] |
quant-ph/0606162
|
Boris Ravaine
|
Boris Ravaine, Andrei Derevianko, P.R. Berman
|
Quantum computing with magnetic atoms in optical lattices of reduced
periodicity
| null | null |
10.1103/PhysRevA.74.022330
| null |
quant-ph physics.atom-ph
| null |
We investigate the feasibility of combining Raman optical lattices with a
quantum computing architecture based on lattice-confined magnetically
interacting neutral atoms. A particular advantage of the standing Raman field
lattices comes from reduced interatomic separations leading to increased
interatomic interactions and improved multi-qubit gate performance.
Specifically, we analyze a $J=3/2$ Zeeman system placed in $% \sigma
_{+}-\sigma_{-}$ Raman fields which exhibit $\lambda /4$ periodicity. We find
that the resulting CNOT gate operations times are in the order of millisecond.
We also investigate motional and magnetic-field induced decoherences specific
to the proposed architecture.
|
[
{
"version": "v1",
"created": "Tue, 20 Jun 2006 06:31:43 GMT"
},
{
"version": "v2",
"created": "Sat, 24 Jun 2006 22:28:15 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Ravaine",
"Boris",
""
],
[
"Derevianko",
"Andrei",
""
],
[
"Berman",
"P. R.",
""
]
] |
quant-ph/0606163
|
Antonino Messina
|
F. Palumbo, A. Napoli, and A. Messina
|
Interpreting concurrence in terms of covariances in a generalized spin
star system
|
7 pages, 3 figures, submitted to Phys Rev B
| null | null | null |
quant-ph
| null |
The quantum dynamics of M pairwise coupled spin 1/2 is analyzed and the time
evolution of the entanglement get established within a prefixed couple of spins
is studied. A conceptual and quantitative link between the concurrence function
and measurable quantities is brought to light providing a physical
interpretation for the concurrence itself as well as a way to measure it. A
generalized spin star system is exactly investigated showing that the
entanglement accompanying its rich dynamics is traceable back to the covariance
of appropriate commuting observables of the two spins.
|
[
{
"version": "v1",
"created": "Tue, 20 Jun 2006 08:31:43 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Palumbo",
"F.",
""
],
[
"Napoli",
"A.",
""
],
[
"Messina",
"A.",
""
]
] |
quant-ph/0606164
|
Giuseppe Bimonte
|
Giuseppe Bimonte
|
On large thermal magnetic fluctuations at the surface of metals and the
Casimir force between real metals at nonzero temperature
|
The paper has been withdrawn
| null | null |
DSF 16/2006
|
quant-ph cond-mat.soft hep-th
| null |
This paper has been withdrawn, because relevant publications, related to the
subject of the paper, were overlooked by the author.
|
[
{
"version": "v1",
"created": "Tue, 20 Jun 2006 09:00:52 GMT"
},
{
"version": "v2",
"created": "Fri, 23 Jun 2006 10:21:32 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Bimonte",
"Giuseppe",
""
]
] |
quant-ph/0606165
|
John Calsamiglia
|
E. Bagan, J. Calsamiglia, R. Demkowicz-Dobrzanski, R. Munoz-Tapia
|
How to hide a secret direction
|
4 pages, 1 figure
|
New J. Phys. 9 (2007) 244
|
10.1088/1367-2630/9/8/244
| null |
quant-ph
| null |
We present a procedure to share a secret spatial direction in the absence of
a common reference frame using a multipartite quantum state. The procedure
guarantees that the parties can determine the direction if they perform joint
measurements on the state, but fail to do so if they restrict themselves to
local operations and classical communication (LOCC). We calculate the fidelity
for joint measurements, give bounds on the fidelity achievable by LOCC, and
prove that there is a non-vanishing gap between the two of them, even in the
limit of infinitely many copies. The robustness of the procedure under particle
loss is also studied. As a by-product we find bounds on the probability of
discriminating by LOCC between the invariant subspaces of total angular
momentum N/2 and N/2-1 in a system of N elementary spins.
|
[
{
"version": "v1",
"created": "Tue, 20 Jun 2006 11:18:23 GMT"
}
] | 2007-08-02T00:00:00 |
[
[
"Bagan",
"E.",
""
],
[
"Calsamiglia",
"J.",
""
],
[
"Demkowicz-Dobrzanski",
"R.",
""
],
[
"Munoz-Tapia",
"R.",
""
]
] |
quant-ph/0606166
|
Miloslav Znojil
|
Miloslav Znojil
|
Spiked potentials and quantum toboggans
|
revision: 22 pp, 1 fig
|
J. Phys. A: Math. Gen. 39 (2006) 13325-13336
|
10.1088/0305-4470/39/42/008
| null |
quant-ph
| null |
Even if the motion of a quantum (quasi-)particle proceeds along a
left-right-symmetric (PT-symmetric) curved path in complex plane, the spectrum
of bound states may remain physical, i.e., real and bounded below). We propose
a generalization. Firstly, we show how the topologically less trivial
(tobogganic) contours may be allowed to live on several sheets of a Riemann
surface. Secondly, the specification of a scattering regime is formulated for
such a class of models.
|
[
{
"version": "v1",
"created": "Tue, 20 Jun 2006 12:29:33 GMT"
},
{
"version": "v2",
"created": "Mon, 21 Aug 2006 12:14:50 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Znojil",
"Miloslav",
""
]
] |
quant-ph/0606167
|
Annalisa Marzuoli
|
S. Garnerone, A. Marzuoli, M. Rasetti
|
An efficient quantum algorithm for colored Jones polynomials
|
9 pages, 5 figures
| null | null | null |
quant-ph
| null |
We construct a quantum algorithm to approximate efficiently the colored Jones
polynomial of the plat presentation of any oriented link L at a fixed root of
unity q. Our construction is based on SU(2) Chern-Simons topological quantum
field theory (and associated Wess-Zumino-Witten conformal field theory) and
exploits the q-deformed spin network as computational background.
As proved in (S. Garnerone, A. Marzuoli, M. Rasetti, quant-ph/0601169), the
colored Jones polynomial can be evaluated in a number of elementary steps,
bounded from above by a linear function of the number of crossings of the link,
and polynomially bounded with respect to the number of link strands. Here we
show that the Kaul unitary representation of colored oriented braids used there
can be efficiently approximated on a standard quantum circuit.
|
[
{
"version": "v1",
"created": "Tue, 20 Jun 2006 14:18:00 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Garnerone",
"S.",
""
],
[
"Marzuoli",
"A.",
""
],
[
"Rasetti",
"M.",
""
]
] |
quant-ph/0606168
|
Somshubhro Bandyopadhyay
|
Somshubhro Bandyopadhyay, Gilad Gour and Barry C. Sanders
|
Duality for monogamy of entanglement
|
12 pages
|
Journal of Mathematical Physics 48: 012108 (13 pp.), 31 January
2007,
|
10.1063/1.2435088
| null |
quant-ph
| null |
We establish duality for monogamy of entanglement: whereas monogamy of
entanglement inequalities provide an upper bound for bipartite sharability of
entanglement in a multipartite system, we prove that the same quantity provides
a \emph{lower} bound for distribution of bipartite entanglement in a
multipartite system.
Our theorem for monogamy of entanglement is used to establish relations
between bipartite entanglement that separate one qubit from the rest vs
separating two qubits from the rest.
|
[
{
"version": "v1",
"created": "Tue, 20 Jun 2006 21:16:53 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Bandyopadhyay",
"Somshubhro",
""
],
[
"Gour",
"Gilad",
""
],
[
"Sanders",
"Barry C.",
""
]
] |
quant-ph/0606169
|
Xiao Zheng
|
Xiao Zheng, Fan Wang, and GuanHua Chen
|
A First-Principles Method for Open Electronic Systems
|
10 pages, 6 figures
| null | null | null |
quant-ph
| null |
We prove that the electron density function of a real physical system can be
uniquely determined by its values on any finite subsystem. This establishes the
existence of a rigorous density-functional theory for any open electronic
system. By introducing a new density functional for dissipative interactions
between the reduced system and its environment, we subsequently develop a
time-dependent density-functional theory which depends in principle only on the
electron density of the reduced system. In the steady-state limit, the
conventional first-principles nonequilibrium Green's function formulation for
the current is recovered. A practical scheme is proposed for the new density
functional: the wide-band limit approximation, which is applied to simulate the
transient current through a model molecular device.
|
[
{
"version": "v1",
"created": "Tue, 20 Jun 2006 15:11:33 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Zheng",
"Xiao",
""
],
[
"Wang",
"Fan",
""
],
[
"Chen",
"GuanHua",
""
]
] |
quant-ph/0606170
|
Daryl Achilles
|
Daryl Achilles, Christine Silberhorn, and Ian A. Walmsley
|
Direct, Loss-Tolerant Characterization of Nonclassical Photon Statistics
|
5 pages, 2 figures
|
Phys. Rev. Lett. 97, 043602 (2006)
|
10.1103/PhysRevLett.97.043602
| null |
quant-ph
| null |
We experimentally investigate a method of directly characterizing the photon
number distribution of nonclassical light beams that is tolerant to losses and
makes use only of standard binary detectors. This is achieved in a single
measurement by calibrating the detector using some small amount of prior
information about the source. We demonstrate the technique on a freely
propagating heralded two-photon number state created by conditional detection
of a two-mode squeezed state generated by a parametric downconverter.
|
[
{
"version": "v1",
"created": "Tue, 20 Jun 2006 15:16:04 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Achilles",
"Daryl",
""
],
[
"Silberhorn",
"Christine",
""
],
[
"Walmsley",
"Ian A.",
""
]
] |
quant-ph/0606171
|
Pawel Kurzynski
|
Pawel Kurzynski
|
Relativistic effects in quantum walks: Klein's paradox and
Zitterbewegung
|
4 pages, 3 figures
|
Phys. Lett. A 372, 6125 (2008)
|
10.1016/j.physleta.2008.08.017
| null |
quant-ph
| null |
Quantum walks are not only algorithmic tools for quantum computation but also
not trivial models which describe various physical processes. The paper
compares one-dimensional version of the free particle Dirac equation with
discrete time quantum walk (DTQW). We show that the discretized Dirac equation
when compared with DTQW results in interesting relations. It is also shown that
two relativistic effects associated with the Dirac equation, namely
Zitterbewegung (quivering motion) and Klein's paradox, are present in DTQW,
which can be implemented within non-relativistic quantum mechanics.
|
[
{
"version": "v1",
"created": "Tue, 20 Jun 2006 19:55:52 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Kurzynski",
"Pawel",
""
]
] |
quant-ph/0606172
|
Miguel Socolovsky
|
Stella Huerfano, Sarira Sahu and M. Socolovsky
|
Quantum Mechanics and the Weak Equivalence Principle
|
8 pages, 2 eps figures
| null | null | null |
quant-ph
| null |
We use the Feynman path integral approach to nonrelativistic quantum
mechanics twofold. First, we derive the lagrangian for a spinless particle
moving in a uniformly but not necessarily constantly accelerated reference
frame; then, applying the strong equivalence principle (SEP) we obtain the
Schroedinger equation for a particle in an inertial frame and in the presence
of a uniform and constant gravity field. Second, using the associated Feynman
propagator, we propagate an initial gaussian wave packet, with the final wave
function and probability density depending on the ratio m/hbar, where m is the
inertial mass of the particle, thus exhibiting the fact that the weak
equivalence principle (WEP) is violated by quantum mechanics. Although due to
rapid oscillations the wave function does not exist in the classical limit, the
probability density is well defined and mass independent when hbar goes to 0,
showing the recovery of the WEP. Finally, at the quantum level, a heavier
particle does not necessarily falls faster than a lighter one; this depends on
the relations between the initial and final common positions and times of the
particles.
|
[
{
"version": "v1",
"created": "Tue, 20 Jun 2006 23:53:09 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Huerfano",
"Stella",
""
],
[
"Sahu",
"Sarira",
""
],
[
"Socolovsky",
"M.",
""
]
] |
quant-ph/0606173
|
Ali Mostafazadeh
|
Ali Mostafazadeh
|
Krein-Space Formulation of PT-Symmetry, CPT-Inner Products, and
Pseudo-Hermiticity
|
published version, 17 pages
|
Czech J. Phys. 56, 919-933 (2006)
|
10.1007/s10582-006-0388-8
| null |
quant-ph
| null |
Emphasizing the physical constraints on the formulation of a quantum theory
based on the standard measurement axiom and the Schroedinger equation, we
comment on some conceptual issues arising in the formulation of PT-symmetric
quantum mechanics. In particular, we elaborate on the requirements of the
boundedness of the metric operator and the diagonalizability of the
Hamiltonian. We also provide an accessible account of a Krein-space derivation
of the CPT-inner product that was widely known to mathematicians since 1950's.
We show how this derivation is linked with the pseudo-Hermitian formulation of
PT-symmetric quantum mechanics.
|
[
{
"version": "v1",
"created": "Wed, 21 Jun 2006 07:47:28 GMT"
},
{
"version": "v2",
"created": "Tue, 28 Nov 2006 08:48:03 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Mostafazadeh",
"Ali",
""
]
] |
quant-ph/0606174
|
HyungJin Yang
|
Chang-Ho Hong and Hyung-Jin Yang
|
Comment on "Quantum Dialogue protocol"
|
1figure
| null | null | null |
quant-ph
| null |
In 2004, Ba An Nguyen [Phys. Lett. A 328, 6-10] has presented a Quantum
Dialogue scheme for simultaneously communicating their messages. In this
comment, we show that the quantum dialogue scheme is not secure against the
intercept-and-resend attack and we propose a modified scheme which is secure
against that attack.
|
[
{
"version": "v1",
"created": "Wed, 21 Jun 2006 07:53:44 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Hong",
"Chang-Ho",
""
],
[
"Yang",
"Hyung-Jin",
""
]
] |
quant-ph/0606175
|
Pinaki Roy
|
B.Roy and P.Roy
|
Coherent states of non-Hermitian quantum systems
|
to appear in Phys.Lett A
| null |
10.1016/j.physleta.2006.06.010
| null |
quant-ph
| null |
We use the Gazeau-Klauder formalism to construct coherent states of
non-Hermitian quantum systems. In particular we use this formalism to construct
coherent state of a PT symmetric system. We also discuss construction of
coherent states following Klauder's minimal prescription.
|
[
{
"version": "v1",
"created": "Wed, 21 Jun 2006 09:16:36 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Roy",
"B.",
""
],
[
"Roy",
"P.",
""
]
] |
quant-ph/0606176
|
Wladyslaw A. Majewski
|
W. A. Majewski
|
On non-completely positive quantum dynamical maps on spin chains
|
published; small changes
|
J. Phys. A: Math. Theor. 40 (2007) 11539-11545
|
10.1088/1751-8113/40/38/006
| null |
quant-ph
| null |
The new arguments based on Majorana fermions indicating that non-completely
positive maps can describe open quantum evolution are presented.
|
[
{
"version": "v1",
"created": "Wed, 21 Jun 2006 11:05:21 GMT"
},
{
"version": "v2",
"created": "Fri, 21 Sep 2007 15:44:37 GMT"
}
] | 2011-11-09T00:00:00 |
[
[
"Majewski",
"W. A.",
""
]
] |
quant-ph/0606177
|
Alastair Kay
|
Alastair Kay, Jiannis K. Pachos, Wolfgang D\"ur, Hans J. Briegel
|
Optimal purification of thermal graph states
|
5 pages, 4 figures v2: published version
|
New J. Phys. 8 (2006) 147
|
10.1088/1367-2630/8/8/147
| null |
quant-ph
| null |
In this paper, a purification protocol is presented and its performance is
proven to be optimal when applied to a particular subset of graph states that
are subject to local Z-noise. Such mixed states can be produced by bringing a
system into thermal equilibrium, when it is described by a Hamiltonian which
has a particular graph state as its unique ground state. From this protocol, we
derive the exact value of the critical temperature above which purification is
impossible, as well as the related optimal purification rates. A possible
simulation of graph Hamiltonians is proposed, which requires only bipartite
interactions and local magnetic fields, enabling the tuning of the system
temperature.
|
[
{
"version": "v1",
"created": "Wed, 21 Jun 2006 14:02:54 GMT"
},
{
"version": "v2",
"created": "Wed, 30 Aug 2006 08:12:08 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Kay",
"Alastair",
""
],
[
"Pachos",
"Jiannis K.",
""
],
[
"Dür",
"Wolfgang",
""
],
[
"Briegel",
"Hans J.",
""
]
] |
quant-ph/0606178
|
Vladimir Korepin
|
A. R. Its, B.-Q. Jin and V. E. Korepin
|
Entropy of XY Spin Chain and Block Toeplitz Determinants
|
46 pages, 3 figures
|
Fields Institute Communications, Universality and Renormalization
[editors I.Bender and D. Kreimer], vol 50, page 151, 2007
| null |
YITP-SB-06-24
|
quant-ph math-ph math.MP nlin.SI
| null |
We consider entanglement in the ground state of the XY spin model on infinite
chain. We use von Neumann entropy of a sub-system as a measure of entanglement.
The entropy of a large block of neighboring spins approaches a constant as the
size of the block increases. We prove rigorously expression for limiting
entropy which was published before. We observe that the entropy reaches minimum
at product states but increases boundlessly at phase transitions.
|
[
{
"version": "v1",
"created": "Wed, 21 Jun 2006 16:51:52 GMT"
},
{
"version": "v2",
"created": "Tue, 4 Jul 2006 00:44:43 GMT"
},
{
"version": "v3",
"created": "Mon, 18 Sep 2006 15:14:35 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Its",
"A. R.",
""
],
[
"Jin",
"B. -Q.",
""
],
[
"Korepin",
"V. E.",
""
]
] |
quant-ph/0606179
|
Shengyu Zhang
|
Pawel Wocjan, Shengyu Zhang
|
Several natural BQP-Complete problems
|
13 pages, 4 figures
| null | null | null |
quant-ph
| null |
A central problem in quantum computing is to identify computational tasks
which can be solved substantially faster on a quantum computer than on any
classical computer. By studying the hardest such tasks, known as BQP-complete
problems, we deepen our understanding of the power and limitations of quantum
computers. We present several BQP-complete problems, including Local
Hamiltonian Eigenvalue Sampling and Phase Estimation Sampling. Different than
the previous known BQP-complete problems (the Quadratically Signed Weight
Enumerator problem [KL01] and the Approximation of Jones Polynomials [FKW02,
FLW02, AJL06]), our problems are of a basic linear algebra nature and are
closely related to the well-known quantum algorithm and quantum complexity
theories.
|
[
{
"version": "v1",
"created": "Wed, 21 Jun 2006 20:01:18 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Wocjan",
"Pawel",
""
],
[
"Zhang",
"Shengyu",
""
]
] |
quant-ph/0606180
|
David Wineland
|
D. J. Wineland, J. Britton, R. J. Epstein, D. Leibfried, R. B.
Blakestad, K. Brown, J. D. Jost, C. Langer, R. Ozeri, S. Seidelin, and J.
Wesenberg
|
Cantilever cooling with radio frequency circuits
|
4 pages, 1 figure
| null | null | null |
quant-ph cond-mat.mes-hall
| null |
We consider a method to reduce the kinetic energy in a low-order mode of a
miniature cantilever. If the cantilever contributes to the capacitance of a
driven RF circuit, a force on the cantilever exists due to the electric field
energy stored in the capacitance. If this force acts with an appropriate phase
shift relative to the motion of the cantilever, it can oppose the velocity of
the cantilever, leading to cooling. Such cooling may enable reaching the
quantum regime of cantilever motion.
|
[
{
"version": "v1",
"created": "Wed, 21 Jun 2006 20:53:14 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Wineland",
"D. J.",
""
],
[
"Britton",
"J.",
""
],
[
"Epstein",
"R. J.",
""
],
[
"Leibfried",
"D.",
""
],
[
"Blakestad",
"R. B.",
""
],
[
"Brown",
"K.",
""
],
[
"Jost",
"J. D.",
""
],
[
"Langer",
"C.",
""
],
[
"Ozeri",
"R.",
""
],
[
"Seidelin",
"S.",
""
],
[
"Wesenberg",
"J.",
""
]
] |
quant-ph/0606181
|
Dariusz Chru\'sci\'nski
|
Dariusz Chruscinski, Andrzej Kossakowski
|
Rotationally invariant multipartite states
|
18 pages; new references
|
Open Sys. Information Dyn. 14, 25-40 (2007)
| null | null |
quant-ph
| null |
We construct a class of multipartite states possessing rotational SO(3)
symmetry -- these are states of K spin-j_A particles and K spin-j_B particles.
The construction of symmetric states follows our two recent papers devoted to
unitary and orthogonal multipartite symmetry. We study basic properties of
multipartite SO(3) symmetric states: separability criteria and multi-PPT
conditions.
|
[
{
"version": "v1",
"created": "Thu, 22 Jun 2006 08:32:44 GMT"
},
{
"version": "v2",
"created": "Thu, 6 Jul 2006 09:38:41 GMT"
}
] | 2007-09-17T00:00:00 |
[
[
"Chruscinski",
"Dariusz",
""
],
[
"Kossakowski",
"Andrzej",
""
]
] |
quant-ph/0606182
|
Lech Jakobczyk
|
L. Derkacz, L. Jakobczyk
|
Quantum interference and evolution of entanglement in a system of
three-level atoms
|
6 pages, 8 figures
| null |
10.1103/PhysRevA.74.032313
| null |
quant-ph
| null |
We consider a pair of three-level atoms interacting with the vacuum. The
process of disentanglement due to spontaneous emission and the role of quantum
interference between principal transitions in this process, are analysed. We
show that the presence of interference can slow down disentanglement. In the
limit of maximal interference, some part of initial entanglement can survive.
|
[
{
"version": "v1",
"created": "Thu, 22 Jun 2006 11:32:38 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Derkacz",
"L.",
""
],
[
"Jakobczyk",
"L.",
""
]
] |
quant-ph/0606183
|
Archan S. Majumdar
|
Md. Manirul Ali, A. S. Majumdar, Dipankar Home, Alok Kumar Pan
|
On the quantum analogue of Galileo's leaning tower experiment
|
Latex, 12 pages, 1 figure, uses IOP style, clarifications and
references added
|
Class.Quant.Grav. 23 (2006) 6493-6502
|
10.1088/0264-9381/23/22/024
| null |
quant-ph gr-qc physics.class-ph
| null |
The quantum analogue of Galileo's leaning tower experiment is revisited using
wave packets evolving under the gravitational potential. We first calculate the
position detection probabilities for particles projected upwards against
gravity around the classical turning point and also around the point of initial
projection, which exhibit mass dependence at both these points. We then compute
the mean arrival time of freely falling particles using the quantum probability
current, which also turns out to be mass dependent. The mass dependence of both
the position detection probabilities and the mean arrival time vanish in the
limit of large mass. Thus, compatibility between the weak equivalence principle
and quantum mechanics is recovered in the macroscopic limit of the latter.
|
[
{
"version": "v1",
"created": "Thu, 22 Jun 2006 11:05:02 GMT"
},
{
"version": "v2",
"created": "Sat, 14 Oct 2006 11:21:09 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Ali",
"Md. Manirul",
""
],
[
"Majumdar",
"A. S.",
""
],
[
"Home",
"Dipankar",
""
],
[
"Pan",
"Alok Kumar",
""
]
] |
quant-ph/0606184
|
Raczynski Andrzej
|
A. Raczynski, J. Zaremba and S. Zielinska-Kaniasty
|
Beam splitting and Hong-Ou-Mandel interference for stored light
|
8 pages, 3 figures
| null |
10.1103/PhysRevA.75.013810
| null |
quant-ph
| null |
Storing and release of a quantum light pulse in a medium of atoms in the
tripod configuration are studied. Two complementary sets of control fields are
defined, which lead to independent and complete photon release at two stages.
The system constitutes a new kind of a flexible beam splitter in which the
input and output ports concern photons of the same direction but well separated
in time. A new version of Hong-Ou-Mandel interference is discussed.
|
[
{
"version": "v1",
"created": "Thu, 22 Jun 2006 11:52:39 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Raczynski",
"A.",
""
],
[
"Zaremba",
"J.",
""
],
[
"Zielinska-Kaniasty",
"S.",
""
]
] |
quant-ph/0606185
|
Heinz-Peter Breuer
|
Heinz-Peter Breuer
|
Separability criteria and bounds for entanglement measures
|
8 pages, 2 figures
|
J. Phys. A: Math. Gen. 39, 11847 (2006)
|
10.1088/0305-4470/39/38/010
| null |
quant-ph
| null |
Employing a recently proposed separability criterion we develop analytical
lower bounds for the concurrence and for the entanglement of formation of
bipartite quantum systems. The separability criterion is based on a
nondecomposable positive map which operates on state spaces with even dimension
N >= 4, and leads to a class of nondecomposable optimal entanglement witnesses.
It is shown that the bounds derived here complement and improve the existing
bounds obtained from the criterion of positive partial transposition and from
the realignment criterion.
|
[
{
"version": "v1",
"created": "Thu, 22 Jun 2006 14:05:08 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Breuer",
"Heinz-Peter",
""
]
] |
quant-ph/0606186
|
R. de la Madrid
|
R. de la Madrid
|
On the inconsistency of the Bohm-Gadella theory with quantum mechanics
|
16 pages
|
J.Phys. A: Math. Gen. 39 (2006) 9255-9268
|
10.1088/0305-4470/39/29/017
| null |
quant-ph hep-th math-ph math.MP
| null |
The Bohm-Gadella theory, sometimes referred to as the Time Asymmetric Quantum
Theory of Scattering and Decay, is based on the Hardy axiom. The Hardy axiom
asserts that the solutions of the Lippmann-Schwinger equation are functionals
over spaces of Hardy functions. The preparation-registration arrow of time
provides the physical justification for the Hardy axiom. In this paper, it is
shown that the Hardy axiom is incorrect, because the solutions of the
Lippmann-Schwinger equation do not act on spaces of Hardy functions. It is also
shown that the derivation of the preparation-registration arrow of time is
flawed. Thus, Hardy functions neither appear when we solve the
Lippmann-Schwinger equation nor they should appear. It is also shown that the
Bohm-Gadella theory does not rest on the same physical principles as quantum
mechanics, and that it does not solve any problem that quantum mechanics cannot
solve. The Bohm-Gadella theory must therefore be abandoned.
|
[
{
"version": "v1",
"created": "Thu, 22 Jun 2006 17:14:42 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"de la Madrid",
"R.",
""
]
] |
quant-ph/0606187
|
Alexander Pechen
|
Alexander Pechen, Nikolai Il'in, Feng Shuang, and Herschel Rabitz
|
Quantum control by von Neumann measurements
| null |
Phys. Rev. A 74, 052102 (2006)
|
10.1103/PhysRevA.74.052102
| null |
quant-ph math-ph math.MP
| null |
A general scheme is presented for controlling quantum systems using evolution
driven by non-selective von Neumann measurements, with or without an additional
tailored electromagnetic field. As an example, a 2-level quantum system
controlled by non-selective quantum measurements is considered. The control
goal is to find optimal system observables such that consecutive non-selective
measurement of these observables transforms the system from a given initial
state into a state which maximizes the expected value of a target operator (the
objective). A complete analytical solution is found including explicit
expressions for the optimal measured observables and for the maximal objective
value given any target operator, any initial system density matrix, and any
number of measurements. As an illustration, upper bounds on measurement-induced
population transfer between the ground and the excited states for any number of
measurements are found. The anti-Zeno effect is recovered in the limit of an
infinite number of measurements. In this limit the system becomes completely
controllable. The results establish the degree of control attainable by a
finite number of measurements.
|
[
{
"version": "v1",
"created": "Thu, 22 Jun 2006 17:37:59 GMT"
},
{
"version": "v2",
"created": "Thu, 2 Nov 2006 21:32:51 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Pechen",
"Alexander",
""
],
[
"Il'in",
"Nikolai",
""
],
[
"Shuang",
"Feng",
""
],
[
"Rabitz",
"Herschel",
""
]
] |
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