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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
quant-ph/0608015
|
Matthias Heid
|
Matthias Heid, Norbert L\"utkenhaus
|
Security of coherent state quantum cryptography in the presence of
Gaussian noise
|
12 pages, 5 figures updated version including two-way communication;
changed the definition of the excess noise to match the definition given
earlier (Phys. Rev. Lett. 92, 117901); submitted to PRA; presented at the 8th
International Conference on Quantum Communication, Measurement and Computing,
Tsukuba
|
Phys. Rev. A, 76, 022313 (2007)
|
10.1103/PhysRevA.76.022313
| null |
quant-ph
| null |
We investigate the security against collective attacks of a continuous
variable quantum key distribution scheme in the asymptotic key limit for a
realistic setting. The quantum channel connecting the two honest parties is
assumed to be lossy and imposes Gaussian noise on the observed quadrature
distributions. Secret key rates are given for direct and reverse reconciliation
schemes including postselection in the collective attack scenario. The effect
of a non-ideal error correction and two-way communication in the classical
post-processing step is also taken into account.
|
[
{
"version": "v1",
"created": "Tue, 1 Aug 2006 17:05:43 GMT"
},
{
"version": "v2",
"created": "Wed, 2 Aug 2006 22:10:28 GMT"
},
{
"version": "v3",
"created": "Mon, 11 Dec 2006 22:54:52 GMT"
},
{
"version": "v4",
"created": "Thu, 19 Apr 2007 21:29:26 GMT"
}
] | 2007-12-12T00:00:00 |
[
[
"Heid",
"Matthias",
""
],
[
"Lütkenhaus",
"Norbert",
""
]
] |
quant-ph/0608016
|
Andreas Winter
|
Peter J. Cameron, Ashley Montanaro, Michael W. Newman, Simone
Severini, Andreas Winter
|
On the quantum chromatic number of a graph
|
7 pages, 1 eps figure; revtex4. v2 has some new references; v3 furthe
small improvements
|
Electronic Journal of Combinatorics 14(1), 2007
| null | null |
quant-ph math.CO
| null |
We investigate the notion of quantum chromatic number of a graph, which is
the minimal number of colours necessary in a protocol in which two separated
provers can convince an interrogator with certainty that they have a colouring
of the graph.
After discussing this notion from first principles, we go on to establish
relations with the clique number and orthogonal representations of the graph.
We also prove several general facts about this graph parameter and find large
separations between the clique number and the quantum chromatic number by
looking at random graphs.
Finally, we show that there can be no separation between classical and
quantum chromatic number if the latter is 2, nor if it is 3 in a restricted
quantum model; on the other hand, we exhibit a graph on 18 vertices and 44
edges with chromatic number 5 and quantum chromatic number 4.
|
[
{
"version": "v1",
"created": "Tue, 1 Aug 2006 17:14:16 GMT"
},
{
"version": "v2",
"created": "Fri, 4 Aug 2006 13:25:07 GMT"
},
{
"version": "v3",
"created": "Tue, 26 Sep 2006 01:32:43 GMT"
}
] | 2011-11-09T00:00:00 |
[
[
"Cameron",
"Peter J.",
""
],
[
"Montanaro",
"Ashley",
""
],
[
"Newman",
"Michael W.",
""
],
[
"Severini",
"Simone",
""
],
[
"Winter",
"Andreas",
""
]
] |
quant-ph/0608017
|
Ralf Schutzhold
|
Ralf Sch\"utzhold and Gernot Schaller
|
Adiabatic quantum algorithms as quantum phase transitions: first versus
second order
|
4 pages, 4 figures
| null |
10.1103/PhysRevA.74.060304
| null |
quant-ph
| null |
In the continuum limit (large number of qubits), adiabatic quantum algorithms
display a remarkable similarity to sweeps through quantum phase transitions. We
find that transitions of second or higher order are advantageous in comparison
to those of first order. With this insight, we propose a novel adiabatic
quantum algorithm for the solution of 3-satisfiability (3-SAT) problems (exact
cover), which is significantly faster than previous proposals according to
numerical simulations (up to 20 qubits). These findings suggest that adiabatic
quantum algorithms can solve NP-complete problems such as 3-SAT much faster
than the Grover search routine (yielding a quadratic enhancement), possibly
even with an exponential speed-up. PACS: 03.67.-a, 03.67.Lx, 73.43.Nq,
64.70.-p.
|
[
{
"version": "v1",
"created": "Tue, 1 Aug 2006 18:08:20 GMT"
},
{
"version": "v2",
"created": "Tue, 15 Aug 2006 18:10:51 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Schützhold",
"Ralf",
""
],
[
"Schaller",
"Gernot",
""
]
] |
quant-ph/0608018
|
Ben Reichardt
|
Ben W. Reichardt
|
Postselection threshold against biased noise
|
13 pages, FOCS 2006; conference version
|
Proc. 47th FOCS, 2006, pages 420-428
|
10.1109/FOCS.2006.64
| null |
quant-ph
| null |
The highest current estimates for the amount of noise a quantum computer can
tolerate are based on fault-tolerance schemes relying heavily on postselecting
on no detected errors. However, there has been no proof that these schemes give
even a positive tolerable noise threshold. A technique to prove a positive
threshold, for probabilistic noise models, is presented. The main idea is to
maintain strong control over the distribution of errors in the quantum state at
all times. This distribution has correlations which conceivably could grow out
of control with postselection. But in fact, the error distribution can be
written as a mixture of nearby distributions each satisfying strong
independence properties, so there are no correlations for postselection to
amplify.
|
[
{
"version": "v1",
"created": "Tue, 1 Aug 2006 20:49:23 GMT"
},
{
"version": "v2",
"created": "Mon, 14 Aug 2006 18:14:14 GMT"
}
] | 2012-06-22T00:00:00 |
[
[
"Reichardt",
"Ben W.",
""
]
] |
quant-ph/0608019
|
Alejandro Romanelli
|
A. Romanelli, R. Donangelo
|
Classical search algorithm with resonances in $\sqrt{N}$ cycles
| null |
Physica A 383, 309 (2007)
|
10.1016/j.physa.2007.04.065
| null |
quant-ph
| null |
In this work we use the wave equation to obtain a classical analog of the
quantum search algorithm and we verify that the essence of search algorithms
resides in the establishment of resonances between the initial and the serched
states. In particular we show that, within a set of $N$ vibration modes, it is
possible to excite the searched mode in a number of steps proportional to
$\sqrt N$.
|
[
{
"version": "v1",
"created": "Tue, 1 Aug 2006 20:55:25 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Romanelli",
"A.",
""
],
[
"Donangelo",
"R.",
""
]
] |
quant-ph/0608020
|
Sun Kyung Lee
|
Sun Kyung Lee, Hai-Woong Lee
|
Damped Population Oscillation in a Spontaneously Decaying Two-Level Atom
Coupled to a Monochromatic Field
|
5 pages, 5 figures
| null |
10.1103/PhysRevA.74.063817
| null |
quant-ph physics.optics
| null |
We investigate the time evolution of atomic population in a two-level atom
driven by a monochromatic radiation field, taking spontaneous emission into
account. The Rabi oscillation exhibits amplitude damping in time caused by
spontaneous emission. We show that the semiclassical master equation leads in
general to an overestimation of the damping rate and that a correct
quantitative description of the damped Rabi oscillation can thus be obtained
only with a full quantum mechanical theory.
|
[
{
"version": "v1",
"created": "Wed, 2 Aug 2006 04:58:34 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Lee",
"Sun Kyung",
""
],
[
"Lee",
"Hai-Woong",
""
]
] |
quant-ph/0608021
|
Andrea Viale
|
R. Tumulka, A. Viale, N. Zanghi
|
Reduced coherence in double-slit diffraction of neutrons
|
4 pages LaTeX, 2 figures
|
Phys. Rev. A 75, 055602 (2007)
|
10.1103/PhysRevA.75.055602
| null |
quant-ph
| null |
In diffraction experiments with particle beams, several effects lead to a
fringe visibility reduction of the interference pattern. We theoretically
describe the intensity one can measure in a double-slit setup and compare the
results with the experimental data obtained with cold neutrons. Our conclusion
is that for cold neutrons the fringe visibility reduction is due not to
decoherence, but to initial incoherence.
|
[
{
"version": "v1",
"created": "Wed, 2 Aug 2006 09:22:31 GMT"
},
{
"version": "v2",
"created": "Wed, 28 Mar 2007 13:33:46 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Tumulka",
"R.",
""
],
[
"Viale",
"A.",
""
],
[
"Zanghi",
"N.",
""
]
] |
quant-ph/0608022
|
Masahito Hayashi
|
Masahito Hayashi, Akihisa Tomita, Keiji Matsumoto
|
Statistical analysis on testing of an entangled state based on Poisson
distribution framework
|
This paper is an extended version of the theoretical part of v1 of
quant-ph/0603254.quant-ph/0603254 is revised so that it is more familiar to
experimentalists
|
New J. Phys., 10, 043029, (2008)
|
10.1088/1367-2630/10/4/043029
| null |
quant-ph
| null |
A hypothesis testing scheme for entanglement has been formulated based on the
Poisson distribution framework instead of the POVM framework. Three designs
were proposed to test the entangled states in this framework. The designs were
evaluated in terms of the asymptotic variance. It has been shown that the
optimal time allocation between the coincidence and anti-coincidence
measurement bases improves the conventional testing method. The test can be
further improved by optimizing the time allocation between the anti-coincidence
bases.
|
[
{
"version": "v1",
"created": "Wed, 2 Aug 2006 09:48:43 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Hayashi",
"Masahito",
""
],
[
"Tomita",
"Akihisa",
""
],
[
"Matsumoto",
"Keiji",
""
]
] |
quant-ph/0608023
|
Indranil Chakrabarty ic
|
Indranil Chakrabarty, B.S.Choudhury
|
Impossibility of Probabilistic splitting of quantum information
|
9 pages
| null | null | null |
quant-ph
| null |
We know that we cannot split the information encoded in two non-orthogonal
qubits into complementary parts deterministically. Here we show that each of
the copies of the state randomly selected from a set of non orthogonal linearly
independent states, splitting of quantum information can not be done even
probabilistically. Here in this work we also show that under certain restricted
conditions, we can probabilistically split the quantum information encoded in a
qubit.
|
[
{
"version": "v1",
"created": "Wed, 2 Aug 2006 12:29:40 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Chakrabarty",
"Indranil",
""
],
[
"Choudhury",
"B. S.",
""
]
] |
quant-ph/0608024
|
Isaac Kim
|
Isaac H. Kim
|
Quamtumness, Generalized Spherical 2-Design and Symmetric
Informationally Complete POVM
|
8 pages, accepted to QIC
|
Quant. Inf. Comp Vol. 7, No. 8 (2007) 730--737
| null | null |
quant-ph
| null |
C. A. Fuchs and M. Sasaki defined the quantumness of a set of quantum states
in \cite{Quantumness}, which is closely related to the fidelity loss in
transmission of the quantum states through a classical channel. In
\cite{Fuchs}, Fuchs showed that in $d$-dimensional Hilbert space, minimum
quantumness is $\frac{2}{d+1}$, and this can be achieved by all rays in the
space. He left an open problem, asking whether fewer than $d^2$ states can
achieve this bound. Recently, in a different context, A. J. Scott introduced a
concept of generalized $t$-design in \cite{GenSphet}, which is a natural
generalization of spherical $t$-design. In this paper, we show that the lower
bound on the quantumness can be achieved if and only if the states form a
generalized 2-design. As a corollary, we show that this bound can be only
achieved if the number of states are larger or equal to $d^2$, answering the
open problem. Furthermore, we also show that the minimal set of such ensemble
is Symmetric Informationally Complete POVM(SIC-POVM). This leads to an
equivalence relation between SIC-POVM and minimal set of ensemble achieving
minimal quantumness.
|
[
{
"version": "v1",
"created": "Wed, 2 Aug 2006 15:13:54 GMT"
},
{
"version": "v2",
"created": "Tue, 31 Oct 2006 21:57:31 GMT"
},
{
"version": "v3",
"created": "Sun, 24 Dec 2006 03:28:39 GMT"
},
{
"version": "v4",
"created": "Sun, 25 Mar 2007 15:57:56 GMT"
}
] | 2011-09-19T00:00:00 |
[
[
"Kim",
"Isaac H.",
""
]
] |
quant-ph/0608025
|
L\'eon Brenig
|
L\'eon Brenig
|
Quantum mechanics is a relativity theory
|
submitted to Physical Review Letters
| null | null | null |
quant-ph
| null |
Non-relativistic quantum mechanics is shown to emerge from classical
mechanics through the requirement of a relativity principle based on special
transformations acting on position and momentum uncertainties. These
transformations keep the Heisenberg inequalities invariant and form a group.
They are related to dilatations of space variables provided the quantum
potential is added to the classical Hamiltonian functional. The Schr\"odinger
equation appears to have a nonunitary and nonlinear companion acting in another
time variable. Evolution in this time seems related to the state vector
reduction.
|
[
{
"version": "v1",
"created": "Wed, 2 Aug 2006 17:33:07 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Brenig",
"Léon",
""
]
] |
quant-ph/0608026
|
J\'er\'emie Roland
|
Fr\'ed\'eric Magniez, Ashwin Nayak, J\'er\'emie Roland and Miklos
Santha
|
Search via Quantum Walk
|
21 pages. Various modifications and improvements, especially in
Section 4
|
SIAM Journal on Computing, 40(1):142-164, 2011
|
10.1137/090745854
| null |
quant-ph cs.CC cs.DS
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We propose a new method for designing quantum search algorithms for finding a
"marked" element in the state space of a classical Markov chain. The algorithm
is based on a quantum walk \'a la Szegedy (2004) that is defined in terms of
the Markov chain. The main new idea is to apply quantum phase estimation to the
quantum walk in order to implement an approximate reflection operator. This
operator is then used in an amplitude amplification scheme. As a result we
considerably expand the scope of the previous approaches of Ambainis (2004) and
Szegedy (2004). Our algorithm combines the benefits of these approaches in
terms of being able to find marked elements, incurring the smaller cost of the
two, and being applicable to a larger class of Markov chains. In addition, it
is conceptually simple and avoids some technical difficulties in the previous
analyses of several algorithms based on quantum walk.
|
[
{
"version": "v1",
"created": "Wed, 2 Aug 2006 18:43:09 GMT"
},
{
"version": "v2",
"created": "Mon, 7 Aug 2006 18:09:10 GMT"
},
{
"version": "v3",
"created": "Tue, 28 Nov 2006 08:57:20 GMT"
},
{
"version": "v4",
"created": "Mon, 14 Feb 2011 21:10:39 GMT"
}
] | 2018-03-22T00:00:00 |
[
[
"Magniez",
"Frédéric",
""
],
[
"Nayak",
"Ashwin",
""
],
[
"Roland",
"Jérémie",
""
],
[
"Santha",
"Miklos",
""
]
] |
quant-ph/0608027
|
Igor Devetak
|
Todd Brun, Igor Devetak, Min-Hsiu Hsieh
|
Catalytic quantum error correction
|
30 pages, 10 figures. Notation change: [[n,k;c]] instead of
[[n,k-c;c]]
|
IEEE Transactions on Information Theory 60, 3073 - 3089 (2014)
|
10.1109/TIT.2014.2313559
| null |
quant-ph
| null |
We develop the theory of entanglement-assisted quantum error correcting
(EAQEC) codes, a generalization of the stabilizer formalism to the setting in
which the sender and receiver have access to pre-shared entanglement.
Conventional stabilizer codes are equivalent to dual-containing symplectic
codes. In contrast, EAQEC codes do not require the dual-containing condition,
which greatly simplifies their construction. We show how any quaternary
classical code can be made into a EAQEC code. In particular, efficient modern
codes, like LDPC codes, which attain the Shannon capacity, can be made into
EAQEC codes attaining the hashing bound. In a quantum computation setting,
EAQEC codes give rise to catalytic quantum codes which maintain a region of
inherited noiseless qubits.
We also give an alternative construction of EAQEC codes by making classical
entanglement assisted codes coherent.
|
[
{
"version": "v1",
"created": "Wed, 2 Aug 2006 19:48:16 GMT"
},
{
"version": "v2",
"created": "Thu, 3 Aug 2006 18:24:07 GMT"
}
] | 2022-02-04T00:00:00 |
[
[
"Brun",
"Todd",
""
],
[
"Devetak",
"Igor",
""
],
[
"Hsieh",
"Min-Hsiu",
""
]
] |
quant-ph/0608028
|
Ranjith Nair
|
Horace P. Yuen and Ranjith Nair
|
On the Security of Y-00 under Fast Correlation and Other Attacks on the
Key
| null |
Physics Letters A 364, 112 (2007)
|
10.1016/j.physleta.2006.12.033
| null |
quant-ph
| null |
The potential weakness of the Y-00 direct encryption protocol when the
encryption box ENC in Y-00 is not chosen properly is demonstrated in a fast
correlation attack by S. Donnet et al in Phys. Lett. A 35, 6 (2006) 406-410. In
this paper, we show how this weakness can be eliminated with a proper design of
ENC. In particular, we present a Y-00 configuration that is more secure than
AES under known-plaintext attack. It is also shown that under any
ciphertext-only attack, full information-theoretic security on the Y-00 seed
key is obtained for any ENC when proper deliberate signal randomization is
employed.
|
[
{
"version": "v1",
"created": "Wed, 2 Aug 2006 21:26:22 GMT"
},
{
"version": "v2",
"created": "Mon, 30 Oct 2006 16:42:47 GMT"
}
] | 2017-12-14T00:00:00 |
[
[
"Yuen",
"Horace P.",
""
],
[
"Nair",
"Ranjith",
""
]
] |
quant-ph/0608029
|
Igor Devetak
|
Zhicheng Luo, Igor Devetak
|
Efficiently implementable codes for quantum key expansion
|
4 pages, 1 figure. The new version has the title changed, the
abstract, introduction and conclusion rewritten. To appear in PRA Rapid
Communications
| null |
10.1103/PhysRevA.75.010303
| null |
quant-ph
| null |
The Shor-Preskill proof of the security of the BB84 quantum key distribution
protocol relies on the theoretical existence of good classical error-correcting
codes with the ``dual-containing'' property. A practical implementation of BB84
thus requires explicit and efficiently decodable constructions of such codes,
which are not known. On the other hand, modern coding theory abounds with
non-dual-containing codes with excellent performance and efficient decoding
algorithms. We show that the dual-containing constraint can be lifted at a
small price: instead of a key distribution protocol, an efficiently
implementable key expansion protocol is obtained, capable of increasing the
size of a pre-shared key by a constant factor.
|
[
{
"version": "v1",
"created": "Wed, 2 Aug 2006 21:06:14 GMT"
},
{
"version": "v2",
"created": "Fri, 19 Jan 2007 21:45:15 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Luo",
"Zhicheng",
""
],
[
"Devetak",
"Igor",
""
]
] |
quant-ph/0608030
|
Shun Watanabe
|
Shun Watanabe, Ryutaroh Matsumoto and Tomohiko Uyematsu
|
Security of quantum key distribution protocol with two-way classical
communication assisted by one-time pad encryption
|
12 pages, 2 figure, version 2 corrected typo errors, version 3 added
the analysis of the key rate in the BB84 protocol
| null | null | null |
quant-ph
| null |
In this paper, we consider a quantum key distribution protocol (QKD) with
two-way classical communication that is assisted by one-time pad encryption. We
propose a two-way preprocessing that uses one-time pad encryption by previously
shared secret key, and the net key rate of the QKD with proposed preprocessing
exceeds the key rate of the QKD without it. The preprocessing is reduced to the
entanglement distillation protocol with two-way classical communication and
previously shared EPR pairs (two-way breeding protocol), and the security of
QKD with the preprocessing is guaranteed in the same way as Shor and Preskill's
arguments.
|
[
{
"version": "v1",
"created": "Thu, 3 Aug 2006 01:57:08 GMT"
},
{
"version": "v2",
"created": "Fri, 18 Aug 2006 05:37:50 GMT"
},
{
"version": "v3",
"created": "Tue, 29 Aug 2006 05:22:21 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Watanabe",
"Shun",
""
],
[
"Matsumoto",
"Ryutaroh",
""
],
[
"Uyematsu",
"Tomohiko",
""
]
] |
quant-ph/0608031
|
Wang Zhi Yong
|
Zhi-Yong Wang, Cai-Dong Xiong
|
Arrival Time in Relativistic Quantum Mechanics
|
16 pages, no figure, revised version
|
J. Phys. A: Math. Theor. 40 (2007) 1897-1905
|
10.1088/1751-8113/40/8/014
| null |
quant-ph
| null |
Relativistic free-motion time-of-arrival theory for massive spin-1/2
particles is systematically developed. Contrary to the nonrelativistic
time-of-arrival operator studied thoroughly in previous literatures, the
relativistic time-of-arrival operator possesses self-adjoint extensions because
of the particle-antiparticle symmetry. The nonrelativistic limit of our theory
is in agreement with the nonrelativistic time-of-arrival theory.
|
[
{
"version": "v1",
"created": "Thu, 3 Aug 2006 12:29:08 GMT"
},
{
"version": "v2",
"created": "Tue, 8 Aug 2006 19:55:48 GMT"
},
{
"version": "v3",
"created": "Tue, 15 Aug 2006 14:21:50 GMT"
},
{
"version": "v4",
"created": "Fri, 18 Aug 2006 10:00:17 GMT"
},
{
"version": "v5",
"created": "Fri, 15 Sep 2006 10:40:43 GMT"
},
{
"version": "v6",
"created": "Mon, 9 Oct 2006 13:53:11 GMT"
},
{
"version": "v7",
"created": "Wed, 25 Oct 2006 12:34:42 GMT"
},
{
"version": "v8",
"created": "Tue, 9 Jan 2007 09:41:01 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Wang",
"Zhi-Yong",
""
],
[
"Xiong",
"Cai-Dong",
""
]
] |
quant-ph/0608032
|
Nicolas J. Cerf
|
Raul Garcia-Patron and Nicolas J. Cerf
|
Unconditional optimality of Gaussian attacks against continuous-variable
QKD
|
4 pages, 4 figures
|
Phys. Rev. Lett. 97, 190503 (2006).
|
10.1103/PhysRevLett.97.190503
| null |
quant-ph
| null |
A fully general approach to the security analysis of continuous-variable
quantum key distribution (CV-QKD) is presented. Provided that the quantum
channel is estimated via the covariance matrix of the quadratures, Gaussian
attacks are shown to be optimal against all eavesdropping strategies, including
collective and coherent attacks. The proof is made strikingly simple by
combining a physical model of measurement, an entanglement-based description of
CV-QKD, and a recent powerful result on the extremality of Gaussian states
[Phys. Rev. Lett. 96, 080502 (2006)].
|
[
{
"version": "v1",
"created": "Thu, 3 Aug 2006 17:09:35 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Garcia-Patron",
"Raul",
""
],
[
"Cerf",
"Nicolas J.",
""
]
] |
quant-ph/0608033
|
Diego Dalvit
|
D.A.R. Dalvit, F.C. Lombardo, F.D. Mazzitelli, and R. Onofrio
|
Exact Casimir interaction between eccentric cylinders
|
5 pages, 4 figures
|
Phys. Rev. A 74, 020101(R) (2006)
|
10.1103/PhysRevA.74.020101
| null |
quant-ph
| null |
The Casimir force is the ultimate background in ongoing searches of
extra-gravitational forces in the micrometer range. Eccentric cylinders offer
favorable experimental conditions for such measurements as spurious
gravitational and electrostatic effects can be minimized. Here we report on the
evaluation of the exact Casimir interaction between perfectly conducting
eccentric cylinders using a mode summation technique, and study different
limiting cases of relevance for Casimir force measurements, with potential
implications for the understanding of mechanical properties of nanotubes.
|
[
{
"version": "v1",
"created": "Thu, 3 Aug 2006 14:58:59 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Dalvit",
"D. A. R.",
""
],
[
"Lombardo",
"F. C.",
""
],
[
"Mazzitelli",
"F. D.",
""
],
[
"Onofrio",
"R.",
""
]
] |
quant-ph/0608034
|
Miguel Navascu\'es
|
Miguel Navascues, Frederic Grosshans, and Antonio Acin
|
Optimality of Gaussian Attacks in Continuous Variable Quantum
Cryptography
|
See also R. Garcia-Patron and N. Cerf, quant-ph/0608032
| null |
10.1103/PhysRevLett.97.190502
| null |
quant-ph
| null |
We analyze the asymptotic security of the family of Gaussian modulated
Quantum Key Distribution protocols for Continuous Variables systems. We prove
that the Gaussian unitary attack is optimal for all the considered bounds on
the key rate when the first and second momenta of the canonical variables
involved are known by the honest parties.
|
[
{
"version": "v1",
"created": "Thu, 3 Aug 2006 15:57:09 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Navascues",
"Miguel",
""
],
[
"Grosshans",
"Frederic",
""
],
[
"Acin",
"Antonio",
""
]
] |
quant-ph/0608035
|
Bob Coecke
|
Bob Coecke and Dusko Pavlovic
|
Quantum measurements without sums
|
41 pages and 46 pictures; earlier version circulated since November
2005 with as title "Quantum Measurements as Coalgebras"
|
The Mathematics of Quantum Computation and Technology, pp.559-596,
Chen, Kauffman and Lomonaco (eds.), Taylor and Francis, 2008
| null | null |
quant-ph math.CT math.LO math.QA
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Sums play a prominent role in the formalisms of quantum mechanics, be it for
mixing and superposing states, or for composing state spaces. Surprisingly, a
conceptual analysis of quantum measurement seems to suggest that quantum
mechanics can be done without direct sums, expressed entirely in terms of the
tensor product. The corresponding axioms define classical spaces as objects
that allow copying and deleting data. Indeed, the information exchange between
the quantum and the classical worlds is essentially determined by their
distinct capabilities to copy and delete data. The sums turn out to be an
implicit implementation of this capabilities. Realizing it through explicit
axioms not only dispenses with the unnecessary structural baggage, but also
allows a simple and intuitive graphical calculus. In category-theoretic terms,
classical data types are dagger-compact Frobenius algebras, and quantum spectra
underlying quantum measurements are Eilenberg-Moore coalgebras induced by these
Frobenius algebras.
|
[
{
"version": "v1",
"created": "Thu, 3 Aug 2006 16:53:06 GMT"
},
{
"version": "v2",
"created": "Thu, 7 Aug 2008 18:00:22 GMT"
}
] | 2009-09-29T00:00:00 |
[
[
"Coecke",
"Bob",
""
],
[
"Pavlovic",
"Dusko",
""
]
] |
quant-ph/0608036
|
Mario Cesar Baldiotti
|
V.G. Bagrov, M.C. Baldiotti, D.M. Gitman, A.D. Levin
|
Two interacting spins in external fields. Four-level systems
|
14 pages
|
AnnalenPhys.16:274-285,2007
|
10.1002/andp.200610231
|
IF-1622/2006
|
quant-ph math-ph math.MP nucl-th
| null |
In the present article, we consider the so-called two-spin equation that
describes four-level quantum systems. Recently, these systems attract attention
due to their relation to the problem of quantum computation. We study general
properties of the two-spin equation and show that the problem for certain
external backgrounds can be identified with the problem of one spin in an
appropriate background. This allows one to generate a number of exact solutions
for two-spin equations on the basis of already known exact solutions of the
one-spin equation. Besides, we present some exact solutions for the two-spin
equation with an external background different for each spin but having the
same direction. We study the eigenvalue problem for a time-independent spin
interaction and a time-independent external background. A possible analogue of
the Rabi problem for the two-spin equation is defined. We present its exact
solution and demonstrate the existence of magnetic resonances in two specific
frequencies, one of them coinciding with the Rabi frequency, and the other
depending on the rotating field magnitude. The resonance that corresponds to
the second frequency is suppressed with respect to the first one.
|
[
{
"version": "v1",
"created": "Thu, 3 Aug 2006 21:46:47 GMT"
}
] | 2008-11-26T00:00:00 |
[
[
"Bagrov",
"V. G.",
""
],
[
"Baldiotti",
"M. C.",
""
],
[
"Gitman",
"D. M.",
""
],
[
"Levin",
"A. D.",
""
]
] |
quant-ph/0608037
|
Stephen D. Bartlett
|
Agata M. Branczyk, Paulo E. M. F. Mendonca, Alexei Gilchrist, Andrew
C. Doherty, and Stephen D. Bartlett
|
Quantum Control of a Single Qubit
|
12 pages, 7 figures, v2 includes new references and minor changes
|
Phys. Rev. A, 75, 012329 (2007)
|
10.1103/PhysRevA.75.012329
| null |
quant-ph
| null |
Measurements in quantum mechanics cannot perfectly distinguish all states and
necessarily disturb the measured system. We present and analyse a proposal to
demonstrate fundamental limits on quantum control of a single qubit arising
from these properties of quantum measurements. We consider a qubit prepared in
one of two non-orthogonal states and subsequently subjected to dephasing noise.
The task is to use measurement and feedback control to attempt to correct the
state of the qubit. We demonstrate that projective measurements are not optimal
for this task, and that there exists a non-projective measurement with an
optimum measurement strength which achieves the best trade-off between gaining
information about the system and disturbing it through measurement back-action.
We study the performance of a quantum control scheme that makes use of this
weak measurement followed by feedback control, and demonstrate that it realises
the optimal recovery from noise for this system. We contrast this approach with
various classically inspired control schemes.
|
[
{
"version": "v1",
"created": "Fri, 4 Aug 2006 04:34:05 GMT"
},
{
"version": "v2",
"created": "Tue, 15 Aug 2006 07:04:18 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Branczyk",
"Agata M.",
""
],
[
"Mendonca",
"Paulo E. M. F.",
""
],
[
"Gilchrist",
"Alexei",
""
],
[
"Doherty",
"Andrew C.",
""
],
[
"Bartlett",
"Stephen D.",
""
]
] |
quant-ph/0608038
|
Palma Guillermo Prof. Dr.
|
G. Palma and U. Raff
|
The one dimensional Hydrogen atom revisited
|
Accepted for publication in the Canadian Journal of Physics, July
28th, 2006
| null |
10.1139/P06-072
| null |
quant-ph
| null |
The one dimensional Schroedinger hydrogen atom is an interesting mathematical
and physical problem to study bound states, eigenfunctions and quantum
degeneracy issues. This 1D physical system gave rise to some intriguing
controversy over more than four decades. Presently, still no definite consensus
seems to have been reached. We reanalyzed this apparently controversial
problem, approaching it from a Fourier transform representation method combined
with some fundamental (basic) ideas found in self-adjoint extensions of
symmetric operators. In disagreement with some previous claims, we found that
the complete Balmer energy spectrum is obtained together with an odd parity set
of eigenfunctions. Closed form solutions in both coordinate and momentum spaces
were obtained. No twofold degeneracy was observed as predicted by the
degeneracy theorem in one dimension, though it does not necessarily have to
hold for potentials with singularities. No ground state with infinite energy
exists since the corresponding eigenfunction does not satisfy the Schroedinger
equation at the origin.
|
[
{
"version": "v1",
"created": "Fri, 4 Aug 2006 16:09:44 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Palma",
"G.",
""
],
[
"Raff",
"U.",
""
]
] |
quant-ph/0608039
|
Yosuke Okudaira
|
Alberto Carlini, Akio Hosoya, Tatsuhiko Koike and Yosuke Okudaira
|
Time Optimal Unitary Operations
|
4 pages, 1 figure. References added
|
Phys. Rev. A 75, 042308 (2007)
|
10.1103/PhysRevA.75.042308
| null |
quant-ph
| null |
Extending our previous work on time optimal quantum state evolution, we
formulate a variational principle for the time optimal unitary operation, which
has direct relevance to quantum computation. We demonstrate our method with
three examples, i.e. the swap of qubits, the quantum Fourier transform and the
entangler gate, by choosing a two-qubit anisotropic Heisenberg model.
|
[
{
"version": "v1",
"created": "Fri, 4 Aug 2006 07:44:46 GMT"
},
{
"version": "v2",
"created": "Sat, 5 Aug 2006 09:24:58 GMT"
},
{
"version": "v3",
"created": "Fri, 18 Aug 2006 06:39:26 GMT"
},
{
"version": "v4",
"created": "Wed, 11 Apr 2007 06:29:45 GMT"
}
] | 2014-12-01T00:00:00 |
[
[
"Carlini",
"Alberto",
""
],
[
"Hosoya",
"Akio",
""
],
[
"Koike",
"Tatsuhiko",
""
],
[
"Okudaira",
"Yosuke",
""
]
] |
quant-ph/0608040
|
Ming-Yong Ye
|
Ming-Yong Ye, Wei Jiang, Ping-Xing Chen, Yong-Sheng Zhang, Zheng-Wei
Zhou, and Guang-Can Guo
|
Local Distinguishability of Orthogonal Quantum States and Generators of
SU(N)
|
some discussions added
|
PHYSICAL REVIEW A 76, 032329 (2007)
|
10.1103/PhysRevA.76.032329
| null |
quant-ph
| null |
We investigate the possibility of distinguishing a set of mutually orthogonal
multipartite quantum states by local operations and classical communication
(LOCC). We connect this problem with generators of SU(N) and present a new
condition that is necessary for a set of orthogonal states to be locally
distinguishable. We show that even in multipartite cases there exists a
systematic way to check whether the presented condition is satisfied for a
given set of orthogonal states. Based on the proposed checking method, we find
that LOCC cannot distinguish three mutually orthogonal states in which two of
them are GHZ-like states.
|
[
{
"version": "v1",
"created": "Fri, 4 Aug 2006 10:59:44 GMT"
},
{
"version": "v2",
"created": "Mon, 7 Jan 2008 08:16:45 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Ye",
"Ming-Yong",
""
],
[
"Jiang",
"Wei",
""
],
[
"Chen",
"Ping-Xing",
""
],
[
"Zhang",
"Yong-Sheng",
""
],
[
"Zhou",
"Zheng-Wei",
""
],
[
"Guo",
"Guang-Can",
""
]
] |
quant-ph/0608041
|
Christian Kothe
|
Christian Kothe, Gunnar Bj\"ork
|
Entanglement quantification through local observable correlations
|
5 pages, 3 figures, revised version with new proof and replaced
figures
|
Phys. Rev. A 75, 012336 (2007)
|
10.1103/PhysRevA.75.012336
| null |
quant-ph
| null |
We present a significantly improved scheme of entanglement detection inspired
by local uncertainty relations for a system consisting of two qubits.
Developing the underlying idea of local uncertainty relations, namely
correlations, we demonstrate that it's possible to define a measure which is
invariant under local unitary transformations and which is based only on local
measurements. It is quite simple to implement experimentally and it allows
entanglement quantification in a certain range for mixed states and exactly for
pure states, without first obtaining full knowledge (e.g. through tomography)
of the state.
|
[
{
"version": "v1",
"created": "Fri, 4 Aug 2006 11:33:20 GMT"
},
{
"version": "v2",
"created": "Tue, 24 Oct 2006 14:49:50 GMT"
}
] | 2016-08-16T00:00:00 |
[
[
"Kothe",
"Christian",
""
],
[
"Björk",
"Gunnar",
""
]
] |
quant-ph/0608042
|
Lorenzo Maccone
|
Giulio Chiribella, Lorenzo Maccone, Paolo Perinotti
|
Secret quantum communication of a reference frame
|
4 pages, no figures; published version
|
Phys. Phys, Rev. Lett. 98, 120501 (2007)
|
10.1103/PhysRevLett.98.120501
| null |
quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
We propose quantum cryptographic protocols to secretly communicate a
reference frame- unspeakable information in the sense it cannot be encoded into
a string of bits. Two distant parties can secretly align their Cartesian axes
by exchanging N spin 1/2 particles, achieving the optimal accuracy 1/N. A
possible eavesdropper cannot gain any information without being detected.
|
[
{
"version": "v1",
"created": "Fri, 4 Aug 2006 14:22:42 GMT"
},
{
"version": "v2",
"created": "Wed, 22 Oct 2008 14:07:34 GMT"
}
] | 2008-10-22T00:00:00 |
[
[
"Chiribella",
"Giulio",
""
],
[
"Maccone",
"Lorenzo",
""
],
[
"Perinotti",
"Paolo",
""
]
] |
quant-ph/0608043
|
Peter Maunz
|
L. Deslauriers, M. Acton, B. B. Blinov, K.-A. Brickman, P. C. Haljan,
W. K. Hensinger, D. Hucul, S. Katnik, R. N. Kohn, Jr., P. J. Lee, M. J.
Madsen, P. Maunz, S. Olmschenk, D. L. Moehring, D. Stick, J. Sterk, M. Yeo,
K. C. Younge, C. Monroe
|
Efficient Photoionization-Loading of Trapped Cadmium Ions with Ultrafast
Pulses
|
11 pages, 12 figures
| null |
10.1103/PhysRevA.74.063421
| null |
quant-ph
| null |
Atomic cadmium ions are loaded into radiofrequency ion traps by
photoionization of atoms in a cadmium vapor with ultrafast laser pulses. The
photoionization is driven through an intermediate atomic resonance with a
frequency-quadrupled mode-locked Ti:Sapphire laser that produces pulses of
either 100 fsec or 1 psec duration at a central wavelength of 229 nm. The large
bandwidth of the pulses photoionizes all velocity classes of the Cd vapor,
resulting in high loading efficiencies compared to previous ion trap loading
techniques. Measured loading rates are compared with a simple theoretical
model, and we conclude that this technique can potentially ionize every atom
traversing the laser beam within the trapping volume. This may allow the
operation of ion traps with lower levels of background pressures and less trap
electrode surface contamination. The technique and laser system reported here
should be applicable to loading most laser-cooled ion species.
|
[
{
"version": "v1",
"created": "Fri, 4 Aug 2006 18:55:46 GMT"
},
{
"version": "v2",
"created": "Fri, 4 Aug 2006 22:00:54 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Deslauriers",
"L.",
""
],
[
"Acton",
"M.",
""
],
[
"Blinov",
"B. B.",
""
],
[
"Brickman",
"K. -A.",
""
],
[
"Haljan",
"P. C.",
""
],
[
"Hensinger",
"W. K.",
""
],
[
"Hucul",
"D.",
""
],
[
"Katnik",
"S.",
""
],
[
"Kohn,",
"R. N.",
"Jr."
],
[
"Lee",
"P. J.",
""
],
[
"Madsen",
"M. J.",
""
],
[
"Maunz",
"P.",
""
],
[
"Olmschenk",
"S.",
""
],
[
"Moehring",
"D. L.",
""
],
[
"Stick",
"D.",
""
],
[
"Sterk",
"J.",
""
],
[
"Yeo",
"M.",
""
],
[
"Younge",
"K. C.",
""
],
[
"Monroe",
"C.",
""
]
] |
quant-ph/0608044
|
Christino Tamon
|
W. Carlson, A. Ford, E. Harris, J. Rosen, C. Tamon, K. Wrobel
|
Universal Mixing of Quantum Walk on Graphs
|
14 pages, 4 figures
|
Quantum Information and Computation 7(8):738-751, 2007
| null | null |
quant-ph
| null |
We study the set of probability distributions visited by a continuous-time
quantum walk on graphs. An edge-weighted graph G is universal mixing if the
instantaneous or average probability distribution of the quantum walk on G
ranges over all probability distributions on the vertices as the weights are
varied over non-negative reals. The graph is uniform mixing if it visits the
uniform distribution. Our results include the following:
(a) All weighted complete multipartite graphs are instantaneous universal
mixing. This is in contrast to the fact that no unweighted complete
multipartite graphs are uniform mixing (except for the four-cycle).
(b) The weighted claw or star graph is a minimally connected instantaneous
universal mixing graph. In fact, as a corollary, the unweighted claw is
instantaneous uniform mixing. This adds a new family of uniform mixing graphs
to a list that so far contains only the hypercubes.
(c) Any weighted graph is average almost-uniform mixing unless its spectral
type is sublinear in the size of the graph. This provides a nearly tight
characterization for average uniform mixing on circulant graphs.
(d) No weighted graphs are average universal mixing. This shows that weights
do not help to achieve average universal mixing, unlike the instantaneous case.
Our proofs exploit the spectra of the underlying weighted graphs and path
collapsing arguments.
|
[
{
"version": "v1",
"created": "Fri, 4 Aug 2006 16:09:10 GMT"
}
] | 2008-06-13T00:00:00 |
[
[
"Carlson",
"W.",
""
],
[
"Ford",
"A.",
""
],
[
"Harris",
"E.",
""
],
[
"Rosen",
"J.",
""
],
[
"Tamon",
"C.",
""
],
[
"Wrobel",
"K.",
""
]
] |
quant-ph/0608045
|
David Kribs
|
David W. Kribs and Robert W. Spekkens
|
Quantum Error Correcting Subsystems are Unitarily Recoverable Subsystems
|
Physical Review A, to appear, 8 pages
|
Phys. Rev. A 74, 042329 (2006)
|
10.1103/PhysRevA.74.042329
| null |
quant-ph
| null |
We show that every correctable subsystem for an arbitrary noise operation can
be recovered by a unitary operation, where the notion of recovery is more
relaxed than the notion of correction insofar as it does not protect the
subsystem from subsequent iterations of the noise. We also demonstrate that in
the case of unital noise operations one can identify a subset of all
correctable subsystems -- those that can be corrected by a single unitary
operation -- as the noiseless subsystems for the composition of the noise
operation with its dual. Using the recently developed structure theory for
noiseless subsystems, the identification of such unitarily correctable
subsystems is reduced to an algebraic exercise.
|
[
{
"version": "v1",
"created": "Fri, 4 Aug 2006 21:31:50 GMT"
},
{
"version": "v2",
"created": "Fri, 29 Sep 2006 21:15:56 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Kribs",
"David W.",
""
],
[
"Spekkens",
"Robert W.",
""
]
] |
quant-ph/0608046
|
Siamak Khademi
|
Siamak Khademi
|
On derivation of Wigner distribution function
| null | null | null | null |
quant-ph
| null |
Wigner distribution function has much importance in quantum statistical
mechanics. It finds applications in various disciplines of physics including
condense matter, quantum optics, to name but a few. Wigner distribution
function is introduced by E. Wigner in 1932. However, there is no analytical
derivation of Wigner distribution function in the literatures, to date. In this
paper, a simple analytical derivation of Wigner distribution function is
presented. Our derivation is based on two assumptions, these are A) by taking
the integral of Wigner distribution function, with respect to configuration
space, the momentum space distribution function is obtained B) WDF is real.
Similarly, and in addition to Wigner distribution function, the distribution
function of Sobouti-Nasiri, which is imaginary, is also derived.
|
[
{
"version": "v1",
"created": "Fri, 4 Aug 2006 23:59:23 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Khademi",
"Siamak",
""
]
] |
quant-ph/0608047
|
Peter Maunz
|
P. Maunz, D. L. Moehring, M. J. Madsen, R. N. Kohn Jr., K. C. Younge,
C. Monroe
|
Quantum Interference of Photon Pairs from Two Trapped Atomic Ions
|
4 pages, 4 figures
| null |
10.1038/nphys644
| null |
quant-ph
| null |
We collect the fluorescence from two trapped atomic ions, and measure quantum
interference between photons emitted from the ions. The interference of two
photons is a crucial component of schemes to entangle atomic qubits based on a
photonic coupling. The ability to preserve the generated entanglement and to
repeat the experiment with the same ions is necessary to implement entangling
quantum gates between atomic qubits, and allows the implementation of protocols
to efficiently scale to larger numbers of atomic qubits.
|
[
{
"version": "v1",
"created": "Sat, 5 Aug 2006 01:19:03 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Maunz",
"P.",
""
],
[
"Moehring",
"D. L.",
""
],
[
"Madsen",
"M. J.",
""
],
[
"Kohn",
"R. N.",
"Jr."
],
[
"Younge",
"K. C.",
""
],
[
"Monroe",
"C.",
""
]
] |
quant-ph/0608048
|
Qi-Ren Zhang
|
Qi-Ren Zhang
|
Some Non-Perturbative and Non-Linear Effects in Laser-Atom Interaction
|
8 pages, 4 figures
| null | null | null |
quant-ph
| null |
We show that if the laser is intense enough, it may always ionize an atom or
induce transitions between discrete energy levels of the atom, no matter what
is its frequency. It means in the quantum transition of an atom interacting
with an intense laser of circular frequency $\omega$, the energy difference
between the initial and the final states of the atom is not necessarily being
an integer multiple of the quantum energy $\hbar\omega$. The absorption spectra
become continuous. The Bohr condition is violated. The energy of photoelectrons
becomes light intensity dependent in the intense laser photoelectric effect.
The transition probabilities and cross sections of photo-excitations and
photo-ionizations are laser intensity dependent, showing that these processes
cannot be reduced to the results of interactions between the atom and separate
individual photons, they are rather the processes of the atom interacting with
the laser as a whole. The interaction of photons on atoms are not simply
additive. The effects are non-perturbative and non-linear. Some numerical
results for processes between hydrogen atom and intense circularly polarized
laser, illustrating the non-perturbative and non-linear character of the
atom-laser interaction, are given.
|
[
{
"version": "v1",
"created": "Sun, 6 Aug 2006 02:21:18 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Zhang",
"Qi-Ren",
""
]
] |
quant-ph/0608049
|
Akbar Fahmi Shakib
|
A. Fahmi and M. Golshani
|
Locality and the Greenberger-Horne-Zeilinger Theorem
|
9 pages, comments welcome
| null | null | null |
quant-ph
| null |
In all local realistic theories worked out till now, locality is considered
as a basic assumption. Most people in the field consider the inconsistency
between local realistic theories and quantum mechanics to be a result of
non-local nature of quantum mechanics. In this Paper, we derive the
Greenberger-Horne-Zeilinger type theorem for particles with instantaneous
(non-local) interactions at the hidden-variable level. Then, we show that the
previous contradiction still exists between quantum mechanics and non-local
hidden variable models.
|
[
{
"version": "v1",
"created": "Sun, 6 Aug 2006 11:49:39 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Fahmi",
"A.",
""
],
[
"Golshani",
"M.",
""
]
] |
quant-ph/0608050
|
Itamar Pitowsky
|
Itamar Pitowsky
|
On the classification of pure multipartite states
|
This paper has been withdrawn
| null | null | null |
quant-ph
| null |
This paper has been withdrawn by the author due to an error.
|
[
{
"version": "v1",
"created": "Sun, 6 Aug 2006 12:25:05 GMT"
},
{
"version": "v2",
"created": "Sat, 9 Sep 2006 11:38:04 GMT"
},
{
"version": "v3",
"created": "Fri, 15 Sep 2006 01:07:06 GMT"
},
{
"version": "v4",
"created": "Wed, 20 Sep 2006 22:37:05 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Pitowsky",
"Itamar",
""
]
] |
quant-ph/0608051
|
Michael Hartmann Mr
|
Michael J. Hartmann, Moritz E. Reuter, Martin B. Plenio
|
Excitation and Entanglement Transfer Near Quantum Critical Points
|
submitted to Optics and Spectroscopy special issue for ICQO'2006
| null |
10.1134/S0030400X0707003X
| null |
quant-ph cond-mat.str-el
| null |
Recently, there has been growing interest in employing condensed matter
systems such as quantum spin or harmonic chains as quantum channels for short
distance communication. Many properties of such chains are determined by the
spectral gap between their ground and excited states. In particular this gap
vanishes at critical points of quantum phase transitions. In this article we
study the relation between the transfer speed and quality of such a system and
the size of its spectral gap. We find that the transfer is almost perfect but
slow for large spectral gaps and fast but rather inefficient for small gaps.
|
[
{
"version": "v1",
"created": "Sun, 6 Aug 2006 15:14:57 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Hartmann",
"Michael J.",
""
],
[
"Reuter",
"Moritz E.",
""
],
[
"Plenio",
"Martin B.",
""
]
] |
quant-ph/0608052
|
Andrew G. White
|
K. J. Resch, J. L. O'Brien, T. J. Weinhold, K. Sanaka, and A. G. White
|
Entanglement generation by Fock-state filtration
|
4 pages, 3 figures
|
Physical Review Letters 98, 203602 (2007)
|
10.1103/PhysRevLett.98.203602
| null |
quant-ph
| null |
We demonstrate a Fock-state filter which is capable of preferentially
blocking single photons over photon pairs. The large conditional nonlinearities
are based on higher-order quantum interference, using linear optics, an ancilla
photon, and measurement. We demonstrate that the filter acts coherently by
using it to convert unentangled photon pairs to a path-entangled state. We
quantify the degree of entanglement by transforming the path information to
polarisation information, applying quantum state tomography we measure a tangle
of T=(20+/-9)%.
|
[
{
"version": "v1",
"created": "Mon, 7 Aug 2006 06:01:26 GMT"
}
] | 2007-06-13T00:00:00 |
[
[
"Resch",
"K. J.",
""
],
[
"O'Brien",
"J. L.",
""
],
[
"Weinhold",
"T. J.",
""
],
[
"Sanaka",
"K.",
""
],
[
"White",
"A. G.",
""
]
] |
quant-ph/0608053
|
Matthias Kleinmann
|
Matthias Kleinmann, Hermann Kampermann, Tim Meyer, and Dagmar Bruss
|
Purifying and Reversible Physical Processes
|
5 pages, no figures, v2: only minimal changes
|
Appl. Phys. B 86, 371 (2007)
|
10.1007/s00340-006-2515-4
| null |
quant-ph
| null |
Starting from the observation that reversible processes cannot increase the
purity of any input state, we study deterministic physical processes, which map
a set of states to a set of pure states. Such a process must map any state to
the same pure output, if purity is demanded for the input set of all states.
But otherwise, when the input set is restricted, it is possible to find
non-trivial purifying processes. For the most restricted case of only two input
states, we completely characterize the output of any such map. We furthermore
consider maps, which combine the property of purity and reversibility on a set
of states, and we derive necessary and sufficient conditions on sets, which
permit such processes.
|
[
{
"version": "v1",
"created": "Mon, 7 Aug 2006 12:15:54 GMT"
},
{
"version": "v2",
"created": "Tue, 12 Dec 2006 10:34:59 GMT"
}
] | 2010-06-30T00:00:00 |
[
[
"Kleinmann",
"Matthias",
""
],
[
"Kampermann",
"Hermann",
""
],
[
"Meyer",
"Tim",
""
],
[
"Bruss",
"Dagmar",
""
]
] |
quant-ph/0608054
|
Ramazan Sever
|
Metin Aktas, Ramazan Sever
|
Effective Mass Schrodinger Equation for Exactly Solvable Class of
One-Dimensional Potentials
|
10 pages
|
J. Math. Chem. 43, 92(2007)
| null | null |
quant-ph
| null |
We deal with the exact solutions of Schrodinger equation characterized by
position-dependent effective mass via point canonical transformations. The
Morse, Poschl-Teller and Hulthen type potentials are considered respectively.
With the choice of position-dependent mass forms, exactly solvable target
potentials are constructed. Their energy of the bound states and corresponding
wavefunctions are determined exactly.
|
[
{
"version": "v1",
"created": "Mon, 7 Aug 2006 07:16:23 GMT"
}
] | 2007-12-27T00:00:00 |
[
[
"Aktas",
"Metin",
""
],
[
"Sever",
"Ramazan",
""
]
] |
quant-ph/0608055
|
Hyunchul Nha
|
Hyunchul Nha and Jaewan Kim
|
Demonstrating multipartite entanglement of single-particle W states:
linear optical schemes
|
5.5 pages, 2 figures, published version with slight modifications
|
Phys. Rev. A 75, 012326 (2007)
|
10.1103/PhysRevA.75.012326
| null |
quant-ph
| null |
We present two linear optical schemes using nonideal photodetectors to
demonstrate inseparability of W-type N-partite entangled states containing only
a single photon. First, we show that the pairwise entanglement of arbitrary two
modes chosen from N optical modes can be detected using the method proposed by
Nha and Kim [Phys. Rev. A 74, 012317 (2006)], thereby suggesting the full
inseparability among N parties. In particular, this scheme is found to succeed
for any nonzero quantum efficiency of photodetectors. Second, we consider a
quantum teleportation network using linear optics without auxiliary modes. The
conditional teleportation can be optimized by a suitable choice of the
transmittance of the beam splitter in the Bell measurement. Specifically, we
identify the conditions under which maximum fidelity larger than classical
bound 2/3 is achieved only in cooperation with other parties. We also
investigate the case of on-off photodetectors that cannot discriminate the
number of detected photons.
|
[
{
"version": "v1",
"created": "Mon, 7 Aug 2006 07:43:13 GMT"
},
{
"version": "v2",
"created": "Wed, 21 Feb 2007 02:55:06 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Nha",
"Hyunchul",
""
],
[
"Kim",
"Jaewan",
""
]
] |
quant-ph/0608056
|
Steven Jones Mr
|
S. J. Jones, H. M. Wiseman, S. D. Bartlett, J. A. Vaccaro, and D. T.
Pope
|
Entanglement and Symmetry: A Case Study in Superselection Rules,
Reference Frames, and Beyond
|
16 pages, 6 figures. v2 updated version published in Phys Rev A
|
Phys. Rev. A 74, 062313 (2006)
|
10.1103/PhysRevA.74.062313
| null |
quant-ph
| null |
This paper concentrates on a particular example of a constraint imposed by
superselection rules (SSRs): that which applies when the parties (Alice and
Bob) cannot distinguish among certain quantum objects they have. This arises
naturally in the context of ensemble quantum information processing such as in
liquid NMR. We discuss how a SSR for the symmetric group can be applied, and
show how the extractable entanglement can be calculated analytically in certain
cases, with a maximum bipartite entanglement in an ensemble of N Bell-state
pairs scaling as log(N) as N goes to infinity . We discuss the apparent
disparity with the asymptotic (N >> 1) recovery of unconstrained entanglement
for other sorts of superselection rules, and show that the disparity disappears
when the correct notion of applying the symmetric group SSR to multiple copies
is used. Next we discuss reference frames in the context of this SSR, showing
the relation to the work of von Korff and Kempe [Phys. Rev. Lett. 93, 260502
(2004)]. The action of a reference frame can be regarded as the analog of
activation in mixed-state entanglement. We also discuss the analog of
distillation: there exist states such that one copy can act as an imperfect
reference frame for another copy. Finally we present an example of a stronger
operational constraint, that operations must be non-collective as well as
symmetric. Even under this stronger constraint we nevertheless show that
Bell-nonlocality (and hence entanglement) can be demonstrated for an ensemble
of N Bell-state pairs no matter how large N is. This last work is a
generalization of that of Mermin [Phys. Rev. D 22, 356 (1980)].
|
[
{
"version": "v1",
"created": "Mon, 7 Aug 2006 10:36:02 GMT"
},
{
"version": "v2",
"created": "Thu, 21 Dec 2006 02:13:18 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Jones",
"S. J.",
""
],
[
"Wiseman",
"H. M.",
""
],
[
"Bartlett",
"S. D.",
""
],
[
"Vaccaro",
"J. A.",
""
],
[
"Pope",
"D. T.",
""
]
] |
quant-ph/0608057
|
Marko Znidaric
|
Tomaz Prosen and Marko Znidaric
|
Is efficiency of classical simulations of quantum dynamics related to
integrability?
|
4 pages; v2. added paragraph discussing pure states
|
Phys.Rev.E 75, 015202 (2007)
|
10.1103/PhysRevE.75.015202
| null |
quant-ph cond-mat.other nlin.SI
| null |
Efficiency of time-evolution of quantum observables, and thermal states of
quenched hamiltonians, is studied using time-dependent density matrix
renormalization group method in a family of generic quantum spin chains which
undergo a transition from integrable to non-integrable - quantum chaotic case
as control parameters are varied. Quantum states (observables) are represented
in terms of matrix-product-operators with rank D_\epsilon(t), such that
evolution of a long chain is accurate within fidelity error \epsilon up to time
t. We find that rank generally increases exponentially, D_\epsilon(t) \propto
\exp(const t), unless the system is integrable in which case we find polynomial
increase.
|
[
{
"version": "v1",
"created": "Mon, 7 Aug 2006 11:25:41 GMT"
},
{
"version": "v2",
"created": "Thu, 14 Sep 2006 11:45:05 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Prosen",
"Tomaz",
""
],
[
"Znidaric",
"Marko",
""
]
] |
quant-ph/0608058
|
Matthias Kleinmann
|
Patrick Skwara, Hermann Kampermann, Matthias Kleinmann, Dagmar Bruss
|
Entanglement witnesses and a loophole problem
|
5 pages, 2 figures, published version
|
Phys. Rev. A 76, 012312 (2007)
|
10.1103/PhysRevA.76.012312
| null |
quant-ph
| null |
We consider a possible detector-efficiency loophole in experiments that
detect entanglement via the local measurement of witness operators. Here, only
local properties of the detectors are known. We derive a general threshold for
the detector efficiencies which guarantees that a negative expectation value of
a witness is due to entanglement, rather than to erroneous detectors. This
threshold depends on the local decomposition of the witness and its measured
expectation value. For two-qubit witnesses we find the local operator
decomposition that is optimal with respect to closing the loophole.
|
[
{
"version": "v1",
"created": "Mon, 7 Aug 2006 14:28:51 GMT"
},
{
"version": "v2",
"created": "Wed, 18 Jul 2007 14:35:26 GMT"
}
] | 2007-07-18T00:00:00 |
[
[
"Skwara",
"Patrick",
""
],
[
"Kampermann",
"Hermann",
""
],
[
"Kleinmann",
"Matthias",
""
],
[
"Bruss",
"Dagmar",
""
]
] |
quant-ph/0608059
|
Marco Cozzini
|
M. Cozzini, P. Giorda, and P. Zanardi
|
Quantum phase transitions and quantum fidelity in free fermion graphs
|
14 pages, 5 figures
| null |
10.1103/PhysRevB.75.014439
| null |
quant-ph cond-mat.str-el
| null |
In this paper we analyze the ground state phase diagram of a class of
fermionic Hamiltonians by looking at the fidelity of ground states
corresponding to slightly different Hamiltonian parameters. The Hamiltonians
under investigation can be considered as the variable range generalization of
the fermionic Hamiltonian obtained by the Jordan-Wigner transformation of the
XY spin-chain in a transverse magnetic field. Under periodic boundary
conditions, the matrices of the problem become circulant and the models are
exactly solvable. Their free-ends counterparts are instead analyzed
numerically. In particular, we focus on the long range model corresponding to a
fully connected directed graph, providing asymptotic results in the
thermodynamic limit, as well as the finite-size scaling analysis of the second
order quantum phase transitions of the system. A strict relation between
fidelity and single particle spectrum is demonstrated, and a peculiar gapful
transition due to the long range nature of the coupling is found. A comparison
between fidelity and another transition marker borrowed from quantum
information i.e., single site entanglement, is also considered.
|
[
{
"version": "v1",
"created": "Mon, 7 Aug 2006 14:57:49 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Cozzini",
"M.",
""
],
[
"Giorda",
"P.",
""
],
[
"Zanardi",
"P.",
""
]
] |
quant-ph/0608060
|
Maarten Van den Nest
|
M. Van den Nest, W. D\"ur, G. Vidal, H. J. Briegel
|
Classical simulation versus universality in measurement based quantum
computation
|
16 pages, 4 figures
|
Phys. Rev. A 75, 012337 (2007)
|
10.1103/PhysRevA.75.012337
| null |
quant-ph
| null |
We investigate for which resource states an efficient classical simulation of
measurement based quantum computation is possible. We show that the
Schmidt--rank width, a measure recently introduced to assess universality of
resource states, plays a crucial role in also this context. We relate
Schmidt--rank width to the optimal description of states in terms of tree
tensor networks and show that an efficient classical simulation of measurement
based quantum computation is possible for all states with logarithmically
bounded Schmidt--rank width (with respect to the system size). For graph states
where the Schmidt--rank width scales in this way, we efficiently construct the
optimal tree tensor network descriptions, and provide several examples. We
highlight parallels in the efficient description of complex systems in quantum
information theory and graph theory.
|
[
{
"version": "v1",
"created": "Mon, 7 Aug 2006 17:21:21 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Nest",
"M. Van den",
""
],
[
"Dür",
"W.",
""
],
[
"Vidal",
"G.",
""
],
[
"Briegel",
"H. J.",
""
]
] |
quant-ph/0608061
|
Anil Shaji
|
Thomas F. Jordan, Anil Shaji and E. C. G. Sudarshan
|
Lorentz transformations that entangle spins and entangle momenta
|
5 Pages, 2 Figures, One new paragraph and reference added
| null |
10.1103/PhysRevA.75.022101
| null |
quant-ph
| null |
Simple examples are presented of Lorentz transformations that entangle the
spins and momenta of two particles with positive mass and spin 1/2. They apply
to indistinguishable particles, produce maximal entanglement from finite
Lorentz transformations of states for finite momenta, and describe entanglement
of spins produced together with entanglement of momenta. From the entanglements
considered, no sum of entanglements is found to be unchanged.
|
[
{
"version": "v1",
"created": "Mon, 7 Aug 2006 20:00:06 GMT"
},
{
"version": "v2",
"created": "Thu, 7 Dec 2006 18:57:22 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Jordan",
"Thomas F.",
""
],
[
"Shaji",
"Anil",
""
],
[
"Sudarshan",
"E. C. G.",
""
]
] |
quant-ph/0608062
|
Santosh Shelly Sharma
|
S. Shelly Sharma and N. K. Sharma
|
The K-way negativities as entanglement measures
|
revtex, 13 pages, 6 figures, Section VII replaced by Sections VII and
VIII, Figures revised and typos corrected
| null | null | null |
quant-ph
| null |
A classification of N-partite states, based on K-way negativities (K=2 to N),
is proposed. The K-way partial transpose with respect to a subsystem is defined
so as to shift the focus to K-way coherences instead of K subsystems of the
composite system. For an N-partite system, the fraction of K-way negativity
contributing to global negativity, is obtained. After minimizing K-way
negativities through local unitary qubit rotations, a combined analysis of
2-way, 3-way and global negativities is shown to provide distinct measures of
genuine tripartite, W-state like and bipartite entanglement, for three qubit
composite system. To illustrate the point, entanglement of three qubit GHZ
class states, W-class states, three boson state and noisy states is analysed.
While genuine N-partite entanglement of a composite system is generated by
N-way coherences, N-partite entanglement in general can be present due to
(K<N)-way coherences as well.
|
[
{
"version": "v1",
"created": "Tue, 8 Aug 2006 03:33:28 GMT"
},
{
"version": "v2",
"created": "Fri, 12 Jan 2007 17:05:00 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Sharma",
"S. Shelly",
""
],
[
"Sharma",
"N. K.",
""
]
] |
quant-ph/0608063
|
Hachiro Fujita
|
Hachiro Fujita
|
Several Classes of Concatenated Quantum Codes: Constructions and Bounds
|
This paper was presented in part at the IEICE Technical Meeting on
Information Theory, Nagoya, Japan, March 2006
| null | null | null |
quant-ph
| null |
In this paper we present several classes of asymptotically good concatenated
quantum codes and derive lower bounds on the minimum distance and rate of the
codes. We compare these bounds with the best-known bound of
Ashikhmin--Litsyn--Tsfasman and Matsumoto. We also give a polynomial-time
decoding algorithm for the codes that can decode up to one fourth of the lower
bound on the minimum distance of the codes.
|
[
{
"version": "v1",
"created": "Tue, 8 Aug 2006 13:48:25 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Fujita",
"Hachiro",
""
]
] |
quant-ph/0608064
|
J\'er\'emie Roland
|
Julien Degorre, Sophie Laplante and J\'er\'emie Roland
|
Simulation of bipartite qudit correlations
|
7 pages
|
Phys. Rev. A 75, 012309 (2007)
|
10.1103/PhysRevA.75.012309
| null |
quant-ph
| null |
We present a protocol to simulate the quantum correlations of an arbitrary
bipartite state, when the parties perform a measurement according to two
traceless binary observables. We show that $\log(d)$ bits of classical
communication is enough on average, where $d$ is the dimension of both systems.
To obtain this result, we use the sampling approach for simulating the quantum
correlations. We discuss how to use this method in the case of qudits.
|
[
{
"version": "v1",
"created": "Tue, 8 Aug 2006 08:12:18 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Degorre",
"Julien",
""
],
[
"Laplante",
"Sophie",
""
],
[
"Roland",
"Jérémie",
""
]
] |
quant-ph/0608065
|
Anton Ramsak
|
A. Ramsak, J. Mravlje, R. Zitko, and J. Bonca
|
Spin qubits in double quantum dots - entanglement versus the Kondo
effect
|
3 figures
|
Phys. Rev. B 74, 241305(R) (2006)
|
10.1103/PhysRevB.74.241305
| null |
quant-ph cond-mat.mes-hall cond-mat.str-el
| null |
We investigate the competition between pair entanglement of two spin qubits
in double quantum dots attached to leads with various topologies and the
separate entanglement of each spin with nearby electrodes. Universal behavior
of entanglement is demonstrated in dependence on the mutual interactions
between the spin qubits, the coupling to their environment, temperature and
magnetic field. As a consequence of quantum phase transition an abrupt switch
between fully entangled and unentangled states takes place when the dots are
coupled in parallel.
|
[
{
"version": "v1",
"created": "Tue, 8 Aug 2006 09:59:55 GMT"
},
{
"version": "v2",
"created": "Thu, 19 Oct 2006 12:07:15 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Ramsak",
"A.",
""
],
[
"Mravlje",
"J.",
""
],
[
"Zitko",
"R.",
""
],
[
"Bonca",
"J.",
""
]
] |
quant-ph/0608066
|
Hiroo Azuma
|
Hiroo Azuma
|
Interaction-free measurement with an imperfect absorber
|
6 pages, 3 eps figures, latex2e; v2: minor corrections; v3: the title
is changed
|
Phys. Rev. A 74, 054301 (2006)
|
10.1103/PhysRevA.74.054301
| null |
quant-ph
| null |
In this paper, we consider interaction-free measurement (IFM) with imperfect
interaction. In the IFM proposed by Kwiat et al., we assume that interaction
between an absorbing object and a probe photon is imperfect, so that the photon
is absorbed with probability 1-\eta (0\leq\eta\leq 1) and it passes by the
object without being absorbed with probability \eta when it approaches close to
the object. We derive the success probability P that we can find the object
without the photon absorbed under the imperfect interaction as a power series
in 1/N, and show the following result: Even if the interaction between the
object and the photon is imperfect, we can let the success probability P of the
IFM get close to unity arbitrarily by making the reflectivity of the beam
splitter larger and increasing the number of the beam splitters. Moreover, we
obtain an approximating equation of P for large N from the derived power series
in 1/N.
|
[
{
"version": "v1",
"created": "Tue, 8 Aug 2006 10:54:17 GMT"
},
{
"version": "v2",
"created": "Wed, 9 Aug 2006 10:13:50 GMT"
},
{
"version": "v3",
"created": "Fri, 6 Oct 2006 00:05:33 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Azuma",
"Hiroo",
""
]
] |
quant-ph/0608067
|
Martin Plenio
|
K.M.R. Audenaert and M.B. Plenio
|
When are correlations quantum? -- Verification and quantification of
entanglement by simple measurements
|
10 pages and 4 figures, material and references added
|
New J. Phys. 8, 266 (2006)
|
10.1088/1367-2630/8/11/266
| null |
quant-ph cond-mat.str-el
| null |
The verification and quantification of experimentally created entanglement by
simple measurements, especially between distant particles, is an important
basic task in quantum processing. When composite systems are subjected to local
measurements the measurement data will exhibit correlations, whether these
systems are classical or quantum. Therefore, the observation of correlations in
the classical measurement record does not automatically imply the presence of
quantum correlations in the system under investigation. In this work we explore
the question of when correlations, or other measurement data, are sufficient to
guarantee the existence of a certain amount of quantum correlations in the
system and when additional information, such as the degree of purity of the
system, is needed to do so. Various measurement settings are discussed, both
numerically and analytically. Exact results and lower bounds on the least
entanglement consistent with the observations are presented. The approach is
suitable both for the bi-partite and the multi-partite setting.
|
[
{
"version": "v1",
"created": "Tue, 8 Aug 2006 11:57:52 GMT"
},
{
"version": "v2",
"created": "Fri, 6 Oct 2006 11:48:36 GMT"
},
{
"version": "v3",
"created": "Wed, 8 Nov 2006 23:42:34 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Audenaert",
"K. M. R.",
""
],
[
"Plenio",
"M. B.",
""
]
] |
quant-ph/0608068
|
Z. D. Wang
|
Xin-Ding Zhang, Q. Zhang, and Z. D. Wang
|
Physical implementation of holonomic quantum computation in
decoherence-free subspaces with trapped ions
|
4 pages, 3 figures. To appear in Phys. Rev. A 74 (2006)
|
Phys. Rev. A 74, 034302 (2006)
|
10.1103/PhysRevA.74.034302
| null |
quant-ph
| null |
We propose a feasible scheme to achieve holonomic quantum computation in a
decoherence-free subspace (DFS) with trapped ions. By the application of
appropriate bichromatic laser fields on the designated ions, we are able to
construct two noncommutable single-qubit gates and one controlled-phase gate
using the holonomic scenario in the encoded DFS.
|
[
{
"version": "v1",
"created": "Tue, 8 Aug 2006 12:14:44 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Zhang",
"Xin-Ding",
""
],
[
"Zhang",
"Q.",
""
],
[
"Wang",
"Z. D.",
""
]
] |
quant-ph/0608069
|
Paolo Amore Dr
|
Paolo Amore, Mayra Cervantes, Francisco M. Fern\'andez
|
Variational collocation on finite intervals
|
12 pages, 8 figures, 1 table
| null |
10.1088/1751-8113/40/43/013
| null |
quant-ph
| null |
In this paper we study a new family of sinc--like functions, defined on an
interval of finite width. These functions, which we call ``little sinc'', are
orthogonal and share many of the properties of the sinc functions. We show that
the little sinc functions supplemented with a variational approach enable one
to obtain accurate results for a variety of problems. We apply them to the
interpolation of functions on finite domain and to the solution of the
Schr\"odinger equation, and compare the performance of present approach with
others.
|
[
{
"version": "v1",
"created": "Tue, 8 Aug 2006 13:17:38 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Amore",
"Paolo",
""
],
[
"Cervantes",
"Mayra",
""
],
[
"Fernández",
"Francisco M.",
""
]
] |
quant-ph/0608070
|
Svozil Karl
|
Sebastian Rieder and Karl Svozil
|
Probability distributions and Gleason's Theorem
|
Presented at the 4th conference on Foundations of Probability and
Physics, held in Vaexjoe, June 4-9, 2006
| null |
10.1063/1.2713462
| null |
quant-ph
| null |
We discuss concrete examples for frame functions and their associated density
operators, as well as for non-Gleason type probability measures.
|
[
{
"version": "v1",
"created": "Tue, 8 Aug 2006 13:54:35 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Rieder",
"Sebastian",
""
],
[
"Svozil",
"Karl",
""
]
] |
quant-ph/0608071
|
David Kribs
|
Cedric Beny, Achim Kempf, and David W. Kribs
|
Generalization of Quantum Error Correction via the Heisenberg Picture
|
5 pages, preprint version
|
Phys. Rev. Lett., 98, 100502 (2007)
|
10.1103/PhysRevLett.98.100502
| null |
quant-ph
| null |
We show that the theory of operator quantum error correction can be naturally
generalized by allowing constraints not only on states but also on observables.
The resulting theory describes the correction of algebras of observables (and
may therefore suitably be called ``operator algebra quantum error
correction''). In particular, the approach provides a framework for the
correction of hybrid quantum-classical information and it does not require the
state to be entirely in one of the corresponding subspaces or subsystems. We
discuss applications to quantum teleportation and to the study of information
flows in quantum interactions.
|
[
{
"version": "v1",
"created": "Tue, 8 Aug 2006 15:35:32 GMT"
},
{
"version": "v2",
"created": "Sat, 10 Mar 2007 16:03:38 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Beny",
"Cedric",
""
],
[
"Kempf",
"Achim",
""
],
[
"Kribs",
"David W.",
""
]
] |
quant-ph/0608072
|
Bob Coecke
|
Bob Coecke and Eric Oliver Paquette
|
POVMs and Naimark's theorem without sums
| null | null | null | null |
quant-ph math-ph math.CT math.MP math.QA
| null |
We provide a definition of POVM in terms of abstract tensor structure only.
It is justified in two distinct manners. i. At this abstract level we are still
able to prove Naimark's theorem, hence establishing a bijective correspondence
between abstract POVMs and abstract projective measurements on an extended
system, and this proof is moreover purely graphical. ii. Our definition
coincides with the usual one for the particular case of the Hilbert space
tensor product. We also point to a very useful normal form result for the
classical object structure introduced in quant-ph/0608035.
|
[
{
"version": "v1",
"created": "Tue, 8 Aug 2006 18:10:10 GMT"
},
{
"version": "v2",
"created": "Mon, 29 Jan 2007 13:39:10 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Coecke",
"Bob",
""
],
[
"Paquette",
"Eric Oliver",
""
]
] |
quant-ph/0608073
|
Morton H. Rubin
|
Morton H. Rubin
|
Comment on a paper by Lapaire and Sipe
| null | null | null | null |
quant-ph
| null |
In a recent paper [quant-ph/0607008] Lapaire and Sipe argue that one can
discuss interference experiments using entangled photons in terms of single
photon wave functions. Furthermore, they argue that contrary to the claim of
the authors of the postponed compensation experiment [2], the single photon
wave functions overlap on the beam splitter when interference is observed. In
this comment, we show that the claim in [2] is correct and we argue that the
idea of single photon wave functions in entangled states is misleading.
|
[
{
"version": "v1",
"created": "Tue, 8 Aug 2006 19:08:39 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Rubin",
"Morton H.",
""
]
] |
quant-ph/0608074
|
Madalin Guta
|
Madalin Guta, Bas Janssens and Jonas Kahn
|
Optimal estimation of qubit states with continuous time measurements
|
32 pages, 3 figures, to appear in Commun. Math. Phys
|
Commun. Math. Phys. 277, 127-160 (2008)
|
10.1007/s00220-007-0357-5
| null |
quant-ph
| null |
We propose an adaptive, two steps strategy, for the estimation of mixed qubit
states. We show that the strategy is optimal in a local minimax sense for the
trace norm distance as well as other locally quadratic figures of merit. Local
minimax optimality means that given $n$ identical qubits, there exists no
estimator which can perform better than the proposed estimator on a
neighborhood of size $n^{-1/2}$ of an arbitrary state. In particular, it is
asymptotically Bayesian optimal for a large class of prior distributions.
We present a physical implementation of the optimal estimation strategy based
on continuous time measurements in a field that couples with the qubits.
The crucial ingredient of the result is the concept of local asymptotic
normality (or LAN) for qubits. This means that, for large $n$, the statistical
model described by $n$ identically prepared qubits is locally equivalent to a
model with only a classical Gaussian distribution and a Gaussian state of a
quantum harmonic oscillator.
The term `local' refers to a shrinking neighborhood around a fixed state
$\rho_{0}$. An essential result is that the neighborhood radius can be chosen
arbitrarily close to $n^{-1/4}$. This allows us to use a two steps procedure by
which we first localize the state within a smaller neighborhood of radius
$n^{-1/2+\epsilon}$, and then use LAN to perform optimal estimation.
|
[
{
"version": "v1",
"created": "Tue, 8 Aug 2006 19:45:21 GMT"
},
{
"version": "v2",
"created": "Tue, 17 Oct 2006 15:17:00 GMT"
},
{
"version": "v3",
"created": "Thu, 24 May 2007 13:03:26 GMT"
}
] | 2011-06-23T00:00:00 |
[
[
"Guta",
"Madalin",
""
],
[
"Janssens",
"Bas",
""
],
[
"Kahn",
"Jonas",
""
]
] |
quant-ph/0608075
|
C. Rangan
|
A.M. Bloch, R.W. Brockett, C. Rangan
|
Finite Controllability of Infinite-Dimensional Quantum Systems
|
This is a much improved version of the paper first submitted to the
arxiv in 2006 that has been under review since 2005. A shortened version of
this paper has been conditionally accepted for publication in IEEE
Transactions in Automatic Control (2009)
| null |
10.1109/TAC.2010.2044273
| null |
quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Quantum phenomena of interest in connection with applications to computation
and communication almost always involve generating specific transfers between
eigenstates, and their linear superpositions. For some quantum systems, such as
spin systems, the quantum evolution equation (the Schr\"{o}dinger equation) is
finite-dimensional and old results on controllability of systems defined on on
Lie groups and quotient spaces provide most of what is needed insofar as
controllability of non-dissipative systems is concerned. However, in an
infinite-dimensional setting, controlling the evolution of quantum systems
often presents difficulties, both conceptual and technical. In this paper we
present a systematic approach to a class of such problems for which it is
possible to avoid some of the technical issues. In particular, we analyze
controllability for infinite-dimensional bilinear systems under assumptions
that make controllability possible using trajectories lying in a nested family
of pre-defined subspaces. This result, which we call the Finite Controllability
Theorem, provides a set of sufficient conditions for controllability in an
infinite-dimensional setting. We consider specific physical systems that are of
interest for quantum computing, and provide insights into the types of quantum
operations (gates) that may be developed.
|
[
{
"version": "v1",
"created": "Wed, 9 Aug 2006 02:43:10 GMT"
},
{
"version": "v2",
"created": "Mon, 7 Sep 2009 13:30:45 GMT"
}
] | 2016-11-18T00:00:00 |
[
[
"Bloch",
"A. M.",
""
],
[
"Brockett",
"R. W.",
""
],
[
"Rangan",
"C.",
""
]
] |
quant-ph/0608076
|
Yuri A. Dabaghian
|
Yu. Dabaghian
|
Spectral statistics for scaling quantum graphs
|
9 pages, 4 figures
| null | null | null |
quant-ph
| null |
The explicit solution to the spectral problem of quantum graphs is used to
obtain the exact distributions of several spectral statistics, such as the
oscillations of the quantum momentum eigenvalues around the average, $\delta
k_{n}=k_{n}-\bar k_{n}$, and the nearest neighbor separations,
$s_{n}=k_{n}-k_{n-1}$.
|
[
{
"version": "v1",
"created": "Wed, 9 Aug 2006 02:56:01 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Dabaghian",
"Yu.",
""
]
] |
quant-ph/0608077
|
Avi Marchewka
|
Er'el Granot, Avi Marchewka
|
Universal potential barrier penetration by initially confined
wavepackets
|
4 pages, 2 figures
| null |
10.1103/PhysRevA.76.012708
| null |
quant-ph
| null |
The dynamics of an initially sharp-boundary wavepacket in the presence of an
arbitrary potential barrier are investigated. It is shown that the penetration
through the barrier is universal in the sense that it depends only on the
values of the wavefunction and its derivatives at the boundary. The dependence
on the derivatives vanishes at long distances from the barrier, where the
dynamics are governed solely by the initial value of the wavefunction at the
boundary.
|
[
{
"version": "v1",
"created": "Wed, 9 Aug 2006 06:53:16 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Granot",
"Er'el",
""
],
[
"Marchewka",
"Avi",
""
]
] |
quant-ph/0608078
|
Nicolas Gisin
|
Pierre Bejot, Jerome Kasparian, Estelle Salmon, Roland Ackermann,
Nicolas Gisin, Jean-Pierre Wolf
|
Laser Noise Reduction in Air
|
8 pages
|
Applied Phys. Lett. 88, 251112, 2006
|
10.1063/1.2216402
| null |
quant-ph
| null |
Fluctuations of the white-light supercontinuum produced by ultrashort laser
pulses in selfguided filaments (spatio-temporal solitons) in air are
investigated. We demonstrate that correlations exist within the white-light
supercontinuum, and that they can be used to significantly reduce the laser
intensity noise by filtering the spectrum. More precisely, the fundamental
wavelength is anticorrelated with the wings of the continuum, while conjugated
wavelength pairs on both sides of the continuum are strongly correlated.
Spectral filtering of the continuum reduces the laser intensity noise by 1.2
dB, showing that fluctuations are rejected to the edges of the spectrum.
|
[
{
"version": "v1",
"created": "Wed, 9 Aug 2006 11:48:47 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Bejot",
"Pierre",
""
],
[
"Kasparian",
"Jerome",
""
],
[
"Salmon",
"Estelle",
""
],
[
"Ackermann",
"Roland",
""
],
[
"Gisin",
"Nicolas",
""
],
[
"Wolf",
"Jean-Pierre",
""
]
] |
quant-ph/0608079
|
Louis Marchildon
|
Louis Marchildon
|
Understanding Long-Distance Quantum Correlations
|
11 pages, contribution to the Beyond the Quantum workshop
| null |
10.1142/9789812771186_0013
| null |
quant-ph
| null |
The interpretation of quantum mechanics (or, for that matter, of any physical
theory) consists in answering the question: How can the world be for the theory
to be true? That question is especially pressing in the case of the
long-distance correlations predicted by Einstein, Podolsky and Rosen, and
rather convincingly established during the past decades in various
laboratories. I will review four different approaches to the understanding of
long-distance quantum correlations: (i) the Copenhagen interpretation and some
of its modern variants; (ii) Bohmian mechanics of spin-carrying particles;
(iii) Cramer's transactional interpretation; and (iv) the Hess-Philipp analysis
of extended parameter spaces.
|
[
{
"version": "v1",
"created": "Wed, 9 Aug 2006 13:33:18 GMT"
}
] | 2017-08-23T00:00:00 |
[
[
"Marchildon",
"Louis",
""
]
] |
quant-ph/0608080
|
Alastair Kay
|
Alastair Kay and Jiannis K. Pachos
|
Multipartite purification protocols: upper and optimal bounds
|
15 pages, 16 figures. v3: published version
|
Phys. Rev. A 75, 062307 (2007)
|
10.1103/PhysRevA.75.062307
| null |
quant-ph
| null |
A method for producing an upper bound for all multipartite purification
protocols is devised, based on knowing the optimal protocol for purifying
bipartite states. When applied to a range of noise models, both local and
correlated, the optimality of certain protocols can be demonstrated for a
variety of graph and valence bond states.
|
[
{
"version": "v1",
"created": "Wed, 9 Aug 2006 14:28:02 GMT"
},
{
"version": "v2",
"created": "Mon, 20 Nov 2006 11:33:16 GMT"
},
{
"version": "v3",
"created": "Fri, 8 Jun 2007 11:32:27 GMT"
}
] | 2007-06-13T00:00:00 |
[
[
"Kay",
"Alastair",
""
],
[
"Pachos",
"Jiannis K.",
""
]
] |
quant-ph/0608081
|
Simone Severini
|
Toufik Mansour, Matthias Schork, and Simone Severini
|
A generalization of boson normal ordering
|
10 pages, 1 (LaTeX) figure
|
Physics Letters A, Volume 364, Issues 3-4, 30 April 2007, Pages
214-220
|
10.1016/j.physleta.2006.12.016
| null |
quant-ph
| null |
In this paper we define generalizations of boson normal ordering. These are
based on the number of contractions whose vertices are next to each other in
the linear representation of the boson operator function. Our main motivation
is to shed further light onto the combinatorics arising from algebraic and Fock
space properties of boson operators.
|
[
{
"version": "v1",
"created": "Wed, 9 Aug 2006 15:58:54 GMT"
},
{
"version": "v2",
"created": "Tue, 12 Dec 2006 17:33:27 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Mansour",
"Toufik",
""
],
[
"Schork",
"Matthias",
""
],
[
"Severini",
"Simone",
""
]
] |
quant-ph/0608082
|
Diego Dalvit
|
D.A.R. Dalvit, R.L. de Matos Filho, and F. Toscano
|
Quantum metrology at the Heisenberg limit with ion traps
|
10 pages, 6 figures
|
New J. Phys. 8 (2006) 276
|
10.1088/1367-2630/8/11/276
| null |
quant-ph
| null |
Sub-Planck phase-space structures in the Wigner function of the motional
degree of freedom of a trapped ion can be used to perform weak force
measurements with Heisenberg-limited sensitivity. We propose methods to
engineer the Hamiltonian of the trapped ion to generate states with such small
scale structures, and we show how to use them in quantum metrology
applications.
|
[
{
"version": "v1",
"created": "Wed, 9 Aug 2006 15:42:00 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Dalvit",
"D. A. R.",
""
],
[
"Filho",
"R. L. de Matos",
""
],
[
"Toscano",
"F.",
""
]
] |
quant-ph/0608083
|
Christian Grosche Dr.
|
Christian Grosche, George S. Pogosyan, Alexei N. Sissakian
|
Path Integral Approach for Superintegrable Potentials on Spaces of
Non-constant Curvature: I. Darboux Spaces DI and DII
| null |
Phys.Part.Nucl.38:299-325,2007
|
10.1134/S1063779607030021
|
DESY 06-113
|
quant-ph
| null |
In this paper the Feynman path integral technique is applied for
superintegrable potentials on two-dimensional spaces of non-constant curvature:
these spaces are Darboux spaces D_I and D_II, respectively. On D_I there are
three and on D_II four such potentials, respectively. We are able to evaluate
the path integral in most of the separating coordinate systems, leading to
expressions for the Green functions, the discrete and continuous
wave-functions, and the discrete energy-spectra. In some cases, however, the
discrete spectrum cannot be stated explicitly, because it is either determined
by a transcendental equation involving parabolic cylinder functions (Darboux
space I), or by a higher order polynomial equation. The solutions on D_I in
particular show that superintegrable systems are not necessarily degenerate. We
can also show how the limiting cases of flat space (constant curvature zero)
and the two-dimensional hyperboloid (constant negative curvature) emerge.
|
[
{
"version": "v1",
"created": "Wed, 9 Aug 2006 19:22:54 GMT"
}
] | 2008-11-26T00:00:00 |
[
[
"Grosche",
"Christian",
""
],
[
"Pogosyan",
"George S.",
""
],
[
"Sissakian",
"Alexei N.",
""
]
] |
quant-ph/0608084
|
Glen Gronniger
|
Glen Gronniger, Brett Barwick, and Herman Batelaan
|
A three grating electron interferometer
|
6 pages 4 figures
| null |
10.1088/1367-2630/8/10/224
| null |
quant-ph
| null |
We report the observation of fringes from a three grating electron
interferometer. Interference fringes have been observed at low energies ranging
from 6 keV to 10 keV. Contrasts of up to 25% are recorded and exceed the
maximal contrast of the classical equivalent, Moire deflectometer. This type of
interferometer could serve as a separate beam Mach-Zehnder interferometer for
low energy electron interferometry experiments.
|
[
{
"version": "v1",
"created": "Wed, 9 Aug 2006 20:17:27 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Gronniger",
"Glen",
""
],
[
"Barwick",
"Brett",
""
],
[
"Batelaan",
"Herman",
""
]
] |
quant-ph/0608085
|
Ben Reichardt
|
Ben W. Reichardt
|
Quantum universality by state distillation
|
24 pages, 4 figures; improved presentation, new stability result
|
Quantum Inf. Comput. 9:1030-1052, 2009
| null | null |
quant-ph
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
Quantum universality can be achieved using classically controlled stabilizer
operations and repeated preparation of certain ancilla states. Which ancilla
states suffice for universality? This "magic states distillation" question is
closely related to quantum fault tolerance. Lower bounds on the noise tolerable
on the ancilla help give lower bounds on the tolerable noise rate threshold for
fault-tolerant computation. Upper bounds show the limits of threshold
upper-bound arguments based on the Gottesman-Knill theorem.
We extend the range of single-qubit mixed states that are known to give
universality, by using a simple parity-checking operation. For applications to
proving threshold lower bounds, certain practical stability characteristics are
often required, and we also show a stable distillation procedure.
No distillation upper bounds are known beyond those given by the
Gottesman-Knill theorem. One might ask whether distillation upper bounds reduce
to upper bounds for single-qubit ancilla states. For multi-qubit pure states
and previously considered two-qubit ancilla states, the answer is yes. However,
we exhibit two-qubit mixed states that are not mixtures of stabilizer states,
but for which every postselected stabilizer reduction from two qubits to one
outputs a mixture of stabilizer states. Distilling such states would require
true multi-qubit state distillation methods.
|
[
{
"version": "v1",
"created": "Wed, 9 Aug 2006 22:48:34 GMT"
},
{
"version": "v2",
"created": "Mon, 13 Jul 2009 20:28:40 GMT"
}
] | 2010-03-22T00:00:00 |
[
[
"Reichardt",
"Ben W.",
""
]
] |
quant-ph/0608086
|
Steve Flammia
|
Animesh Datta, Steven T. Flammia, Anil Shaji, Carlton M. Caves
|
Doubly constrained bounds on the entanglement of formation
|
4 pages, 3 figures
| null | null | null |
quant-ph
| null |
We derive bounds on the entanglement of formation of states of a 4xN
bipartite system using two entanglement monotones constructed from operational
separability criteria. The bounds are used simultaneously as constraints on the
entanglement of formation. One monotone is the negativity, which is based on
the Peres positive-partial-transpose criterion. For the other, we formulate a
monotone based on a separability criterion introduced by Breuer (H.-P. Breuer,
e-print quant-ph/0605036).
|
[
{
"version": "v1",
"created": "Wed, 9 Aug 2006 23:21:24 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Datta",
"Animesh",
""
],
[
"Flammia",
"Steven T.",
""
],
[
"Shaji",
"Anil",
""
],
[
"Caves",
"Carlton M.",
""
]
] |
quant-ph/0608087
|
Willem M. de Muynck
|
Willem M. de Muynck
|
POVMs: a small but important step beyond standard quantum mechanics
|
Contribution to Proceedings of the Workshop `Beyond the quantum',
Leiden, May/June 2006
| null |
10.1142/9789812771186_0005
| null |
quant-ph
| null |
It is the purpose of the present contribution to demonstrate that the
generalization of the concept of a quantum mechanical observable from the
Hermitian operator of standard quantum mechanics to a positive operator-valued
measure is not a peripheral issue, allegedly to be understood in terms of a
trivial nonideality of practical measurement procedures, but that this
generalization touches the very core of quantum mechanics, viz. complementarity
and violation of the Bell inequalities.
|
[
{
"version": "v1",
"created": "Thu, 10 Aug 2006 14:54:25 GMT"
}
] | 2017-08-23T00:00:00 |
[
[
"de Muynck",
"Willem M.",
""
]
] |
quant-ph/0608088
|
Edoardo Milotti
|
S. Bartalucci, S. Bertolucci, M. Bragadireanu, M. Cargnelli, M.
Catitti, C. Curceanu (Petrascu), S. Di Matteo, J.-P. Egger, C. Guaraldo, M.
Iliescu, T. Ishiwatari, M. Laubenstein, J. Marton, E. Milotti, D. Pietreanu,
T. Ponta, D. L. Sirghi, F. Sirghi, L. Sperandio, E. Widmann, J. Zmeskal
|
VIP: An Experiment to Search for a Violation of the Pauli Exclusion
Principle
|
Plenary talk presented by E. Milotti at Meson 2006, Cracow, 9-13 June
2006
| null | null | null |
quant-ph
| null |
The Pauli Exclusion Principle is a basic principle of Quantum Mechanics, and
its validity has never been seriously challenged. However, given its
fundamental standing, it is very important to check it as thoroughly as
possible. Here we describe the VIP (VIolation of the Pauli exclusion principle)
experiment, an improved version of the Ramberg and Snow experiment (E. Ramberg
and G. Snow, {\it Phys. Lett. B} {\bf 238}, 438 (1990)); VIP has just completed
the installation at the Gran Sasso underground laboratory, and aims to test the
Pauli Exclusion Principle for electrons with unprecedented accuracy, down to
$\beta^2/2 \approx 10^{-30} - 10^{-31}$. We report preliminary experimental
results and briefly discuss some of the implications of a possible violation.
|
[
{
"version": "v1",
"created": "Thu, 10 Aug 2006 15:16:49 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Bartalucci",
"S.",
"",
"Petrascu"
],
[
"Bertolucci",
"S.",
"",
"Petrascu"
],
[
"Bragadireanu",
"M.",
"",
"Petrascu"
],
[
"Cargnelli",
"M.",
"",
"Petrascu"
],
[
"Catitti",
"M.",
"",
"Petrascu"
],
[
"Curceanu",
"C.",
"",
"Petrascu"
],
[
"Di Matteo",
"S.",
""
],
[
"Egger",
"J. -P.",
""
],
[
"Guaraldo",
"C.",
""
],
[
"Iliescu",
"M.",
""
],
[
"Ishiwatari",
"T.",
""
],
[
"Laubenstein",
"M.",
""
],
[
"Marton",
"J.",
""
],
[
"Milotti",
"E.",
""
],
[
"Pietreanu",
"D.",
""
],
[
"Ponta",
"T.",
""
],
[
"Sirghi",
"D. L.",
""
],
[
"Sirghi",
"F.",
""
],
[
"Sperandio",
"L.",
""
],
[
"Widmann",
"E.",
""
],
[
"Zmeskal",
"J.",
""
]
] |
quant-ph/0608089
|
Jens Lykke Sorensen
|
Jens L. S{\o}rensen, Ditte M{\o}ller, Theis Iversen, Jakob B. Thomsen,
Frank Jensen, Peter Staanum, Dirk Voigt, Michael Drewsen
|
Efficient coherent internal state transfer in trapped ions using
Stimulated Raman Adiabatic Passage
|
4 pages, 4 figures
| null |
10.1088/1367-2630/8/11/261
| null |
quant-ph
| null |
We demonstrate experimentally how the process of Stimulated Raman Adiabatic
Passage (STIRAP) can be utilized for efficient coherent internal state transfer
in single trapped and laser-cooled $^{40}$Ca$^+$ ions. The transfer from the
D$_{3/2}$ to the D$_{5/2}$ state, is detected by a fluorescence measurement
revealing the population not transfered to the D$_{5/2}$ state. A coherent
population transfer efficiency at the level of 95 % in a setup allowing for the
internal state detection of individual ions in a string has been obtained.
|
[
{
"version": "v1",
"created": "Thu, 10 Aug 2006 07:34:34 GMT"
},
{
"version": "v2",
"created": "Fri, 25 Aug 2006 07:44:48 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Sørensen",
"Jens L.",
""
],
[
"Møller",
"Ditte",
""
],
[
"Iversen",
"Theis",
""
],
[
"Thomsen",
"Jakob B.",
""
],
[
"Jensen",
"Frank",
""
],
[
"Staanum",
"Peter",
""
],
[
"Voigt",
"Dirk",
""
],
[
"Drewsen",
"Michael",
""
]
] |
quant-ph/0608090
|
Maxim Shirokov Evgenyevich
|
M.E.Shirokov
|
The Convex Closure of the Output Entropy of Infinite Dimensional
Channels and the Additivity Problem
|
24 pages
|
Russian Mathematical Surveys, Vol. 61, No. 6, (2006), 1186--1188
| null | null |
quant-ph math-ph math.MP
| null |
The continuity properties of the convex closure of the output entropy of
infinite dimensional channels and their applications to the additivity problem
are considered.
The main result of this paper is the statement that the superadditivity of
the convex closure of the output entropy for all finite dimensional channels
implies the superadditivity of the convex closure of the output entropy for all
infinite dimensional channels, which provides the analogous statements for the
strong superadditivity of the EoF and for the additivity of the minimal output
entropy.
The above result also provides infinite dimensional generalization of Shor's
theorem stated equivalence of different additivity properties.
The superadditivity of the convex closure of the output entropy (and hence
the additivity of the minimal output entropy) for two infinite dimensional
channels with one of them a direct sum of noiseless and entanglement-breaking
channels are derived from the corresponding finite dimensional results.
In the context of the additivity problem some observations concerning
complementary infinite dimensional channels are considered.
|
[
{
"version": "v1",
"created": "Thu, 10 Aug 2006 08:58:38 GMT"
}
] | 2008-12-17T00:00:00 |
[
[
"Shirokov",
"M. E.",
""
]
] |
quant-ph/0608091
|
Zafar Ahmed
|
Zafar Ahmed
|
An ansatz for the eigenstates in PT-symmetric quantum mechanics
|
To appear in Phys. Lett. A, 8 pages
| null |
10.1016/j.physleta.2006.08.030
| null |
quant-ph
| null |
We suggest a general ansatz for the energy-eigenstates when a complex
one-dimensional PT-symmetric potential possesses real discrete spectrum.
Several interesting features of PT-symmetric quantum mechanics have been
brought out using this ansatz.
|
[
{
"version": "v1",
"created": "Thu, 10 Aug 2006 10:41:18 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Ahmed",
"Zafar",
""
]
] |
quant-ph/0608092
|
Dr Arun K. Pati
|
A. K. Pati and P. K. Sahu
|
Sum Uncertainty Relation in Quantum Theory
|
LaTeX file, no figure, 4 pages
| null |
10.1016/j.physleta.2007.03.005
| null |
quant-ph
| null |
We prove a new sum uncertainty relation in quantum theory which states that
the uncertainty in the sum of two or more observables is always less than or
equal to the sum of the uncertainties in corresponding observables. This shows
that the quantum mechanical uncertainty in any observable is a convex function.
We prove that if we have a finite number $N$ of identically prepared quantum
systems, then a joint measurement of any observable gives an error $\sqrt N$
less than that of the individual measurements. This has application in quantum
metrology that aims to give better precision in the parameter estimation.
Furthermore, this proves that a quantum system evolves slowly under the action
of a sum Hamiltonian than the sum of individuals, even if they are
non-commuting.
|
[
{
"version": "v1",
"created": "Thu, 10 Aug 2006 17:23:01 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Pati",
"A. K.",
""
],
[
"Sahu",
"P. K.",
""
]
] |
quant-ph/0608093
|
Jose M. Isidro
|
J.M. Isidro, M.A. de Gosson
|
A gauge theory of quantum mechanics
|
9
|
Mod.Phys.Lett.A22:191-200,2007
|
10.1142/S0217732307022578
| null |
quant-ph math-ph math.MP
| null |
An Abelian gerbe is constructed over classical phase space. The 2-cocycles
defining the gerbe are given by Feynman path integrals whose integrands contain
the exponential of the Poincare-Cartan form. The U(1) gauge group on the gerbe
has a natural interpretation as the invariance group of the Schroedinger
equation on phase space.
|
[
{
"version": "v1",
"created": "Thu, 10 Aug 2006 12:33:47 GMT"
}
] | 2008-11-26T00:00:00 |
[
[
"Isidro",
"J. M.",
""
],
[
"de Gosson",
"M. A.",
""
]
] |
quant-ph/0608094
|
Vyacheslav Shatokhin
|
Vyacheslav Shatokhin
|
Spectrum of coherent backscattering of light by two atoms
|
Presented at XI International Conference on Quantum Optics
| null |
10.1134/S0030400X07080206
| null |
quant-ph
| null |
We study theoretically inelastic spectrum of coherent backscattering of laser
light by two atoms. For an intense laser field, there are frequency domains of
not only constructive but also destructive (self-)interference of the inelastic
photons. We interpret the emergent spectral features using the dressed states
and considering coherent backscattering as a kind of the pump-probe experiment.
|
[
{
"version": "v1",
"created": "Thu, 10 Aug 2006 13:03:49 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Shatokhin",
"Vyacheslav",
""
]
] |
quant-ph/0608095
|
Reinaldo O. Vianna
|
Reinaldo O. Vianna and Andrew C. Doherty
|
Study of the Distillability of Werner States Using Entanglement
Witnesses and Robust Semidefinite Programs
|
16 pages, 2 figures
|
Physical Review A, 74, 052306 (2006)
|
10.1103/PhysRevA.74.052306
| null |
quant-ph
| null |
We use Robust Semidefinite Programs and Entanglement Witnesses to study the
distillability of Werner states. We perform exact numerical calculations which
show 2-undistillability in a region of the state space which was previously
conjectured to be undistillable. We also introduce bases which yield
interesting expressions for the {\em distillability witnesses} and for a tensor
product of Werner states with arbitrary number of copies.
|
[
{
"version": "v1",
"created": "Fri, 11 Aug 2006 02:05:07 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Vianna",
"Reinaldo O.",
""
],
[
"Doherty",
"Andrew C.",
""
]
] |
quant-ph/0608096
|
Adrian Paul Flitney
|
Adrian P. Flitney and Andrew D. Greentree
|
Coalitions in the quantum Minority game: classical cheats and quantum
bullies
|
12 pages, 1 figure
|
Phys. Lett. A 362 (2007) 132--137
|
10.1016/j.physleta.2006.10.007
| null |
quant-ph
| null |
In a one-off Minority game, when a group of players agree to collaborate they
gain an advantage over the remaining players. We consider the advantage
obtained in a quantum Minority game by a coalition sharing an initially
entangled state versus that obtained by a coalition that uses classical
communication to arrive at an optimal group strategy. In a model of the quantum
Minority game where the final measurement basis is randomized, quantum
coalitions outperform classical ones when carried out by up to four players,
but an unrestricted amount of classical communication is better for larger
coalition sizes.
|
[
{
"version": "v1",
"created": "Fri, 11 Aug 2006 06:36:30 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Flitney",
"Adrian P.",
""
],
[
"Greentree",
"Andrew D.",
""
]
] |
quant-ph/0608097
|
Artur Scherer
|
Lajos Diosi, Thomas Konrad, Artur Scherer, Juergen Audretsch
|
Coupled Ito equations of continuous quantum state measurement, and
estimation
|
5 pages, RevTeX4. In version v2 some minor revisions and
clarifications have been incorporated. Moreover, a new reference has been
included. Accepted for publication in Journal of Physics A: Mathematical and
General
|
J. Phys. A: Math. Gen. 39 (2006) L575-L581
|
10.1088/0305-4470/39/40/L01
| null |
quant-ph
| null |
We discuss a non-linear stochastic master equation that governs the
time-evolution of the estimated quantum state. Its differential evolution
corresponds to the infinitesimal updates that depend on the time-continuous
measurement of the true quantum state. The new stochastic master equation
couples to the two standard stochastic differential equations of
time-continuous quantum measurement. For the first time, we can prove that the
calculated estimate almost always converges to the true state, also at
low-efficiency measurements. We show that our single-state theory can be
adapted to weak continuous ensemble measurements as well.
|
[
{
"version": "v1",
"created": "Fri, 11 Aug 2006 10:21:54 GMT"
},
{
"version": "v2",
"created": "Fri, 15 Sep 2006 11:32:36 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Diosi",
"Lajos",
""
],
[
"Konrad",
"Thomas",
""
],
[
"Scherer",
"Artur",
""
],
[
"Audretsch",
"Juergen",
""
]
] |
quant-ph/0608098
|
Karl Surmacz
|
K. Surmacz, J. Nunn, F. C. Waldermann, Z. Wang, I. Walmsley, and D.
Jaksch
|
Entanglement fidelity of quantum memories
|
5 pages, 3 figures
|
Phys. Rev. A (74), 050302(R) (2006)
|
10.1103/PhysRevA.74.050302
| null |
quant-ph
| null |
We introduce a figure of merit for a quantum memory which measures the
preservation of entanglement between a qubit stored in and retrieved from the
memory and an auxiliary qubit. We consider a general quantum memory system
consisting of a medium of two level absorbers, with the qubit to be stored
encoded in a single photon. We derive an analytic expression for our figure of
merit taking into account Gaussian fluctuations in the Hamiltonian parameters,
which for example model inhomogeneous broadening and storage time dephasing.
Finally we specialize to the case of an atomic quantum memory where
fluctuations arise predominantly from Doppler broadening and motional
dephasing.
|
[
{
"version": "v1",
"created": "Fri, 11 Aug 2006 11:20:44 GMT"
},
{
"version": "v2",
"created": "Mon, 30 Oct 2006 09:15:16 GMT"
},
{
"version": "v3",
"created": "Mon, 15 Jan 2007 09:28:11 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Surmacz",
"K.",
""
],
[
"Nunn",
"J.",
""
],
[
"Waldermann",
"F. C.",
""
],
[
"Wang",
"Z.",
""
],
[
"Walmsley",
"I.",
""
],
[
"Jaksch",
"D.",
""
]
] |
quant-ph/0608099
|
Dirk Witthaut
|
D. Witthaut and H. J. Korsch
|
Uniform semiclassical approximations of the nonlinear Schroedinger
equation by a Painleve mapping
| null |
J. Phys. A: Math. Gen. 39, 14687 (2006)
|
10.1088/0305-4470/39/47/012
| null |
quant-ph
| null |
A useful semiclassical method to calculate eigenfunctions of the Schroedinger
equation is the mapping to a well-known ordinary differential equation, as for
example Airy's equation. In this paper we generalize the mapping procedure to
the nonlinear Schroedinger equation or Gross-Pitaevskii equation describing the
macroscopic wave function of a Bose-Einstein condensate. The nonlinear
Schroedinger equation is mapped to the second Painleve equation, which is one
of the best-known differential equations with a cubic nonlinearity. A
quantization condition is derived from the connection formulae of these
functions. Comparison with numerically exact results for a harmonic trap
demonstrates the benefit of the mapping method. Finally we discuss the
influence of a shallow periodic potential on bright soliton solutions by a
mapping to a constant potential.
|
[
{
"version": "v1",
"created": "Fri, 11 Aug 2006 11:58:26 GMT"
}
] | 2008-08-12T00:00:00 |
[
[
"Witthaut",
"D.",
""
],
[
"Korsch",
"H. J.",
""
]
] |
quant-ph/0608100
|
Samir Kunkri
|
Sujit K. Choudhary, Guruprasad Kar, Samir Kunkri and Ramij Rahaman
|
Causality, Joint measurement and Tsirelson's bound
|
8 pages
|
Physics Letters A 371 (2007) 395-398
|
10.1016/j.physleta.2007.06.041
| null |
quant-ph
| null |
Tsirelson showed that $2\sqrt{2}$ is the maximum value that CHSH expression
can take for quantum-correlations [B. S.Tsirelson, Lett. Math. Phys, 4 (1980)
93]. This bound simply follows from the algebra of observables. Recently by
exploiting the physical structure of quantum mechanics like unitarity and
linearity, Buhrman and Massar [H. Buhrman and S.Massar, Phys. Rev. A, 72 (2005)
052103] have established that violation of Tsirelson's bound in quantum
mechanics will imply signalling. We prove the same with the help of realistic
joint measurement in quantum mechanics and a Bell's inequality which has been
derived under the assumption of existence of joint measurement and no
signalling condition.
|
[
{
"version": "v1",
"created": "Fri, 11 Aug 2006 14:00:56 GMT"
},
{
"version": "v2",
"created": "Mon, 31 Mar 2008 06:07:17 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Choudhary",
"Sujit K.",
""
],
[
"Kar",
"Guruprasad",
""
],
[
"Kunkri",
"Samir",
""
],
[
"Rahaman",
"Ramij",
""
]
] |
quant-ph/0608101
|
Robert Koenig
|
Robert Koenig and Barbara M. Terhal
|
The Bounded Storage Model in The Presence of a Quantum Adversary
|
13 pages Latex, v3: discussion of independent randomizers added
|
IEEE Trans. Inf. Th., vol. 54, no. 2 (2008)
|
10.1109/TIT.2007.913245
| null |
quant-ph
| null |
An extractor is a function E that is used to extract randomness. Given an
imperfect random source X and a uniform seed Y, the output E(X,Y) is close to
uniform. We study properties of such functions in the presence of prior quantum
information about X, with a particular focus on cryptographic applications. We
prove that certain extractors are suitable for key expansion in the bounded
storage model where the adversary has a limited amount of quantum memory. For
extractors with one-bit output we show that the extracted bit is essentially
equally secure as in the case where the adversary has classical resources. We
prove the security of certain constructions that output multiple bits in the
bounded storage model.
|
[
{
"version": "v1",
"created": "Fri, 11 Aug 2006 17:22:26 GMT"
},
{
"version": "v2",
"created": "Tue, 29 Aug 2006 19:01:28 GMT"
},
{
"version": "v3",
"created": "Fri, 8 Dec 2006 13:29:31 GMT"
}
] | 2008-02-04T00:00:00 |
[
[
"Koenig",
"Robert",
""
],
[
"Terhal",
"Barbara M.",
""
]
] |
quant-ph/0608102
|
Asish Ganguly
|
A. Ganguly, S. Kuru, J. Negro and L. M. Nieto
|
A study of the bound states for square potential wells with
position-dependent mass
|
To appear in Phys. Lett. A (Present e-mail of A.G:
[email protected])
|
Phys.Lett. A360 (2006) 228-233
|
10.1016/j.physleta.2006.08.032
| null |
quant-ph hep-th math-ph math.MP
| null |
A square potential well with position-dependent mass is studied for bound
states. Applying appropriate matching conditions, a transcendental equation is
derived for the energy eigenvalues. Numerical results are presented graphically
and the variation of the energy of the bound states are calculated as a
function of the well-width and mass.
|
[
{
"version": "v1",
"created": "Fri, 11 Aug 2006 16:33:07 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Ganguly",
"A.",
""
],
[
"Kuru",
"S.",
""
],
[
"Negro",
"J.",
""
],
[
"Nieto",
"L. M.",
""
]
] |
quant-ph/0608103
|
Bernardo Coutinho
|
B. Coutinho dos Santos, C. E. R. Souza, K. Dechoum, and A. Z. Khoury
|
Optical parametric oscillation under injection of orbital angular
momentum
| null | null | null | null |
quant-ph
| null |
We present a theoretical model for the spatial mode dynamics of an optical
parametric oscillator under injection of orbital angular momentum. This process
is then interpreted in terms of an interesting picture based on a Poincare
representation of first order spatial modes. The spatial properties of the
down-converted fields can be easily understood from their symmetries in this
geometric representation. By considering the adiabatic mode conversion of the
injected signal, we also predict the occurrence of a geometric phase
conjugation in the down-converted beams. An experimental setup to measure this
effect is proposed.
|
[
{
"version": "v1",
"created": "Fri, 11 Aug 2006 17:43:05 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Santos",
"B. Coutinho dos",
""
],
[
"Souza",
"C. E. R.",
""
],
[
"Dechoum",
"K.",
""
],
[
"Khoury",
"A. Z.",
""
]
] |
quant-ph/0608104
|
Andrei Rybin Dr
|
A.V. Rybin, I.P. Vadeiko, and A.R. Bishop
|
Slow-light solitons revisited
|
4 pages, 1 figure
| null | null | null |
quant-ph
| null |
We investigate propagation of slow-light solitons in atomic media described
by the nonlinear $\Lambda$-model. Under a physical assumption, appropriate to
the slow light propagation, we reduce the $\Lambda$-scheme to a simplified
nonlinear model, which is also relevant to 2D dilatonic gravity. Exact
solutions describing various regimes of stopping slow-light solitons can then
be readily derived.
|
[
{
"version": "v1",
"created": "Fri, 11 Aug 2006 17:06:03 GMT"
},
{
"version": "v2",
"created": "Wed, 16 Aug 2006 08:48:14 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Rybin",
"A. V.",
""
],
[
"Vadeiko",
"I. P.",
""
],
[
"Bishop",
"A. R.",
""
]
] |
quant-ph/0608105
|
Li-Xiang Cen
|
Li-Xiang Cen, Bang-Pin Hou and Ming-Lun Chen
|
Implementation of qutrit-based quantum information processing via
state-dependent forces on trapped ions
|
4 pages, no figure
| null | null | null |
quant-ph
| null |
We propose a scheme to realize quantum logic and entanglement for qutrit
systems via state-dependent forces on trapped ions. By exploiting the laser-ion
coupling in the presence of Coulomb interactions, the set of quantum gate
operations including the conditional phase shifts on two qutrits as well as
arbitrary SU(3) rotations on single qutrits are derived for universal quantum
manipulation. As an illustration, we demonstrate in detail how these gate
resources could be used to generate the maximally entangled state of two
qutrits. Besides being insensitive to vibrational heating of the trapped ions,
the present scheme is also shown to be scalable through designing appropriately
the pulse configuration of the laser-ion interactions.
|
[
{
"version": "v1",
"created": "Sat, 12 Aug 2006 08:27:33 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Cen",
"Li-Xiang",
""
],
[
"Hou",
"Bang-Pin",
""
],
[
"Chen",
"Ming-Lun",
""
]
] |
quant-ph/0608106
|
Vladimir Korepin
|
Byung-Soo Choi and Vladimir Korepin
|
Quantum Partial Search of a Database with Several Target Items
|
13 pages
|
Quantum Information Processing, vol 6, Number 4, page 37, 2007
| null |
YITP- SB- 06-34
|
quant-ph
| null |
We consider a database separated into blocks. Blocks containing target items
are called target blocks. Blocks without target items are called non-target
blocks. We consider a case, when each target block has the same number of
target items. We present a fast quantum algorithm, which finds one of the
target blocks. Our algorithm is based on Grover-Radhakrishnan algorithm of
partial search. We minimize the number of queries to the oracle.
|
[
{
"version": "v1",
"created": "Fri, 11 Aug 2006 20:48:44 GMT"
},
{
"version": "v2",
"created": "Thu, 12 Oct 2006 14:21:54 GMT"
}
] | 2007-06-06T00:00:00 |
[
[
"Choi",
"Byung-Soo",
""
],
[
"Korepin",
"Vladimir",
""
]
] |
quant-ph/0608107
|
Tomasz Luczak
|
A. Wojcik, T. Luczak, P. Kurzynski, A. Grudka, T. Gdala, M. Bednarska
|
Multiuser quantum communication networks
|
5 pages, 5 figures
| null |
10.1103/PhysRevA.75.022330
| null |
quant-ph
| null |
We study a quantum state transfer between spins interacting with an arbitrary
network of spins coupled by uniform XX interactions. It is shown that in such a
system under fairly general conditions, we can expect a nearly perfect transfer
of states. Then we analyze a generalization of this model to the case of many
network users, where the sender can choose which party he wants to communicate
with by appropriately tuning his local magnetic field. We also remark that a
similar idea can be used to create an entanglement between several spins
coupled to the network.
|
[
{
"version": "v1",
"created": "Sat, 12 Aug 2006 07:21:15 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Wojcik",
"A.",
""
],
[
"Luczak",
"T.",
""
],
[
"Kurzynski",
"P.",
""
],
[
"Grudka",
"A.",
""
],
[
"Gdala",
"T.",
""
],
[
"Bednarska",
"M.",
""
]
] |
quant-ph/0608108
|
Yb Gao
|
Y. B. Gao and C. P. Sun
|
Factorization of Dephasing Process in Quantum Open System
|
6 pages, 4 figures
|
Phys. Rev. E 75, 011105 (2007)
|
10.1103/PhysRevE.75.011105
| null |
quant-ph
| null |
The fluctuation-dissipation relation is well known for the quantum open
system with energy dissipation. In this paper a similar underlying relation is
found between the bath fluctuation and the dephasing of the quantum open
system, of which energy is conserved, but the information is leaking into the
bath. To obtain this relation we revisit the universal, but simple dephasing
model with quantum non-demolition interaction between the bath and the open
system. Then we show that the decoherence factor describing the dephasing
process is factorized into two parts, to indicate the two sources of dephasing,
the vacuum quantum fluctuation and the thermal excitations defined in the
initial state of finite temperature.
|
[
{
"version": "v1",
"created": "Sat, 12 Aug 2006 13:18:39 GMT"
},
{
"version": "v2",
"created": "Fri, 18 Aug 2006 08:05:23 GMT"
},
{
"version": "v3",
"created": "Sun, 20 Aug 2006 08:57:47 GMT"
},
{
"version": "v4",
"created": "Sun, 19 Nov 2006 14:08:53 GMT"
}
] | 2013-05-29T00:00:00 |
[
[
"Gao",
"Y. B.",
""
],
[
"Sun",
"C. P.",
""
]
] |
quant-ph/0608109
|
Zhang Peng
|
M. Zhang, P. Zhang, M. S. Chapman and L. you
|
Controlled splitting of an atomic wave packet
|
4 pages, 4 figures. Accepted by Phys. Rev. Lett
|
Phys. Rev. Lett. 97, 070403 (2006)
|
10.1103/PhysRevLett.97.070403
| null |
quant-ph cond-mat.other
| null |
We propose a simple scheme capable of adiabatically splitting an atomic wave
packet using two independent translating traps. Implemented with optical dipole
traps, our scheme allows a high degree of flexibility for atom interferometry
arrangements and highlights its potential as an efficient and high fidelity
atom optical beam splitter.
|
[
{
"version": "v1",
"created": "Sun, 13 Aug 2006 07:22:55 GMT"
},
{
"version": "v2",
"created": "Wed, 16 Aug 2006 15:24:31 GMT"
},
{
"version": "v3",
"created": "Mon, 9 Oct 2006 15:53:13 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Zhang",
"M.",
""
],
[
"Zhang",
"P.",
""
],
[
"Chapman",
"M. S.",
""
],
[
"you",
"L.",
""
]
] |
quant-ph/0608110
|
Eleni Diamanti
|
Eleni Diamanti, Hiroki Takesue, Carsten Langrock, M. M. Fejer,
Yoshihisa Yamamoto
|
100 km secure differential phase shift quantum key distribution with low
jitter up-conversion detectors
|
10 pages, 5 figures
|
Optics Express 14, 13073 (2006)
|
10.1364/OE.14.013073
| null |
quant-ph
| null |
We present a quantum key distribution experiment in which keys that were
secure against all individual eavesdropping attacks allowed by quantum
mechanics were distributed over 100 km of optical fiber. We implemented the
differential phase shift quantum key distribution protocol and used low timing
jitter 1.55 um single-photon detectors based on frequency up-conversion in
periodically poled lithium niobate waveguides and silicon avalanche
photodiodes. Based on the security analysis of the protocol against general
individual attacks, we generated secure keys at a practical rate of 166 bit/s
over 100 km of fiber. The use of the low jitter detectors also increased the
sifted key generation rate to 2 Mbit/s over 10 km of fiber.
|
[
{
"version": "v1",
"created": "Sun, 13 Aug 2006 11:35:16 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Diamanti",
"Eleni",
""
],
[
"Takesue",
"Hiroki",
""
],
[
"Langrock",
"Carsten",
""
],
[
"Fejer",
"M. M.",
""
],
[
"Yamamoto",
"Yoshihisa",
""
]
] |
quant-ph/0608111
|
X.L. Zhang
|
X.L. Zhang, K.L. Gao, M. Feng
|
Preparation of cluster states and W states with superconducting-
quantum-interference-device qubits in cavity QED
|
6 pages, 3 figures, to appear in Phys. Rev. A
|
Phys. Rev. A 74, 024303 (2006)
|
10.1103/PhysRevA.74.024303
| null |
quant-ph
| null |
We propose schemes to create cluster states and W states by many
superconducting-quantum-interference-device (SQUID) qubits in cavities under
the influence of the cavity decay. Our schemes do not require auxiliary qubits,
and the excited levels are only virtually coupled throughout the scheme, which
could much reduce the experimental challenge. We consider the cavity decay in
our model and analytically demonstrate its detrimental influence on the
prepared entangled states.
|
[
{
"version": "v1",
"created": "Mon, 14 Aug 2006 04:01:33 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Zhang",
"X. L.",
""
],
[
"Gao",
"K. L.",
""
],
[
"Feng",
"M.",
""
]
] |
quant-ph/0608112
|
Ashley Stephens
|
A. M. Stephens, S. J. Devitt, A. G. Fowler, J. C. Ang, L. C. L.
Hollenberg
|
Gate-level simulation of logical state preparation
|
8 pages, 2 figures
| null | null | null |
quant-ph
| null |
Quantum error correction and fault-tolerant quantum computation are two
fundamental concepts which make quantum computing feasible. While providing a
theoretical means with which to ensure the arbitrary accuracy of any quantum
circuit, fault-tolerant error correction is predicated upon the robust
preparation of logical states. An optimal direct circuit and a more complex
fault-tolerant circuit for the preparation of the [[7,1,3]] Steane logical-zero
are simulated in the presence of discrete quantum errors to quantify the regime
within which fault-tolerant preparation of logical states is preferred.
|
[
{
"version": "v1",
"created": "Mon, 14 Aug 2006 09:47:01 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Stephens",
"A. M.",
""
],
[
"Devitt",
"S. J.",
""
],
[
"Fowler",
"A. G.",
""
],
[
"Ang",
"J. C.",
""
],
[
"Hollenberg",
"L. C. L.",
""
]
] |
quant-ph/0608113
|
John Jeffers
|
John Jeffers
|
Retrodictive fidelities for pure state postselectors
|
8 Pages, 5 Figs. Accepted version, typos corrected
|
New J. Phys. 8, 268 (2006)
|
10.1088/1367-2630/8/11/268
| null |
quant-ph
| null |
Two measures of fidelity are proposed for postselecting devices, the
retrodictive conditional probability that the state in the measurement arm is
the one indicated by the detectors, and the probability that the device
produces the state that it would produce if working perfectly. The first is the
natural quantity that one wishes to maximise to improve the device operation.
The second corresponds more closely with the accurate operation of the device
than the more usual overlap-based fidelity. The results are particularly
applicable to the types of state preparation and logic gate operation in linear
optical quantum computing.
|
[
{
"version": "v1",
"created": "Mon, 14 Aug 2006 13:03:45 GMT"
},
{
"version": "v2",
"created": "Tue, 24 Oct 2006 13:10:14 GMT"
},
{
"version": "v3",
"created": "Fri, 10 Nov 2006 14:35:48 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Jeffers",
"John",
""
]
] |
quant-ph/0608114
|
Perola Milman
|
P\'erola Milman
|
Phase Dynamics of Two Entangled Qubits
|
9 figures, slightly different version from the accepted one
|
Phys. Rev. A 73, 062118 (2006)
|
10.1103/PhysRevA.73.062118
| null |
quant-ph
| null |
We make a geometric study of the phases acquired by a general pure bipartite
two level system after a cyclic unitary evolution. The geometric representation
of the two particle Hilbert space makes use of Hopf fibrations. It allows for a
simple description of the dynamics of the entangled state's phase during the
whole evolution. The global phase after a cyclic evolution is always an entire
multiple of $\pi$ for all bipartite states, a result that does not depend on
the degree of entanglement. There are three different types of phases combining
themselves so as to result in the $n \pi$ global phase. They can be identified
as dynamical, geometrical and topological. Each one of them can be easily
identified using the presented geometric description. The interplay between
them depends on the initial state and on its trajectory and the results
obtained are shown to be in connection to those on mixed states phases.
|
[
{
"version": "v1",
"created": "Mon, 14 Aug 2006 14:12:29 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Milman",
"Pérola",
""
]
] |
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