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2025-04-04 00:00:00
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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
quant-ph/0603244
|
Andrzej Grudka
|
Andrzej Grudka, Antoni Wojcik, Mikolaj Czechlewski
|
Probabilistic coding of quantum states
| null |
Phys. Rev. A 74, 012302 (2006)
|
10.1103/PhysRevA.74.012302
| null |
quant-ph
| null |
We discuss properties of probabilistic coding of two qubits to one qutrit and
generalize the scheme to higher dimensions. We show that the protocol
preservers entanglement between qubits to be encoded and environment and can be
also applied to mixed states. We present the protocol which enables encoding of
n qudits to one qudit of dimension smaller than the Hilbert space of the
original system and then probabilistically but error-free decode any subset of
k qudits. We give a formula for the probability of successful decoding.
|
[
{
"version": "v1",
"created": "Mon, 27 Mar 2006 13:25:05 GMT"
}
] | 2008-07-24T00:00:00 |
[
[
"Grudka",
"Andrzej",
""
],
[
"Wojcik",
"Antoni",
""
],
[
"Czechlewski",
"Mikolaj",
""
]
] |
quant-ph/0603245
|
Carlo Presilla
|
Giovanni Jona-Lasinio, Carlo Presilla
|
On the statistics of quantum expectations for systems in thermal
equilibrium
|
6 pages, 2 figures, contribution to Quantum Jumps Conference
|
AIP Conf.Proc.844:200-205,2006
|
10.1063/1.2219363
| null |
quant-ph cond-mat.stat-mech hep-th math-ph math.MP physics.chem-ph
| null |
The recent remarkable developments in quantum optics, mesoscopic and cold
atom physics have given reality to wave functions. It is then interesting to
explore the consequences of assuming ensembles over the wave functions simply
related to the canonical density matrix. In this note we analyze a previously
introduced distribution over wave functions which naturally arises considering
the Schroedinger equation as an infinite dimensional dynamical system. In
particular, we discuss the low temperature fluctuations of the quantum
expectations of coordinates and momenta for a particle in a double well
potential. Our results may be of interest in the study of chiral molecules.
|
[
{
"version": "v1",
"created": "Mon, 27 Mar 2006 18:19:40 GMT"
}
] | 2010-12-13T00:00:00 |
[
[
"Jona-Lasinio",
"Giovanni",
""
],
[
"Presilla",
"Carlo",
""
]
] |
quant-ph/0603246
|
Constantino Utreras-D\'iaz A
|
H\'ector Calisto (Universidad de Tarapac\'a), and C. A. Utreras-D\'iaz
(Universidad de Tarapac\'a)
|
On Dynamical Quantization
| null | null | null | null |
quant-ph
| null |
In this article we review some results obtained from a generalization of
quantum mechanics obtained from modification of the canonical commutation
relation $[q,p]={\rm i}\hbar$. We present some new results concerning
relativistic generalizations of previous works, and we calculate the energy
spectrum of some simple quantum systems, using the position and momentum
operators of this new formalism.
|
[
{
"version": "v1",
"created": "Mon, 27 Mar 2006 15:11:11 GMT"
}
] | 2016-08-16T00:00:00 |
[
[
"Calisto",
"Héctor",
"",
"Universidad de Tarapacá"
],
[
"Utreras-Díaz",
"C. A.",
"",
"Universidad de Tarapacá"
]
] |
quant-ph/0603247
|
Leonid A. Krivitsky
|
G. Brida, M.V. Chekhova, M. Genovese, M. Gramegna and L.A. Krivitsky
|
Dispersion spreading of biphotons in optical fibres and two-photon
interference
|
Accepted for publication in Phys.Rev.Lett
|
Phys. Rev. Lett. 96, 143601 (2006)
|
10.1103/PhysRevLett.96.143601
| null |
quant-ph
| null |
We present the first observation of two-photon polarization interference
structure in the second-order Glauber's correlation function of two-photon
light generated via type-II spontaneous parametric down-conversion. In order to
obtain this result, two-photon light is transmitted through an optical fibre
and the coincidence distribution is analyzed by means of the START-STOP method.
Beyond the experimental demonstration of an interesting effect in quantum
optics, these results also have considerable relevance for quantum
communications.
|
[
{
"version": "v1",
"created": "Mon, 27 Mar 2006 15:15:57 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Brida",
"G.",
""
],
[
"Chekhova",
"M. V.",
""
],
[
"Genovese",
"M.",
""
],
[
"Gramegna",
"M.",
""
],
[
"Krivitsky",
"L. A.",
""
]
] |
quant-ph/0603248
|
Camille Negrevergne
|
C. Negrevergne (1), T.S. Mahesh (2), C. A. Ryan (1), M. Ditty (1), F.
Cyr-Racine (1), W. Power (1), N. Boulant (2), T. Havel (2), D.G. Cory (2) and
R. Laflamme (1) ((1) IQC, (2) MIT)
|
Benchmarking quantum control methods on a 12-qubit system
|
11 pages, 4 figures, to be published in PRL
| null |
10.1103/PhysRevLett.96.170501
| null |
quant-ph
| null |
In this letter, we present an experimental benchmark of operational control
methods in quantum information processors extended up to 12 qubits. We
implement universal control of this large Hilbert space using two complementary
approaches and discuss their accuracy and scalability. Despite decoherence, we
were able to reach a 12-coherence state (or 12-qubits pseudo-pure cat state),
and decode it into an 11 qubit plus one qutrit labeled observable pseudo-pure
state using liquid state nuclear magnetic resonance quantum information
processors.
|
[
{
"version": "v1",
"created": "Mon, 27 Mar 2006 15:51:43 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Negrevergne",
"C.",
"",
"IQC"
],
[
"Mahesh",
"T. S.",
"",
"MIT"
],
[
"Ryan",
"C. A.",
"",
"IQC"
],
[
"Ditty",
"M.",
"",
"IQC"
],
[
"Cyr-Racine",
"F.",
"",
"IQC"
],
[
"Power",
"W.",
"",
"IQC"
],
[
"Boulant",
"N.",
"",
"MIT"
],
[
"Havel",
"T.",
"",
"MIT"
],
[
"Cory",
"D. G.",
"",
"MIT"
],
[
"Laflamme",
"R.",
"",
"IQC"
]
] |
quant-ph/0603249
|
Mahmoud Abdel-Aty
|
Mahmoud Abdel-Aty
|
Generation of long-living entanglement using cold trapped ions with pair
cat states
|
15 pages, 7 figures, Sub. Appl. Phys. B: Laser and Optics
| null |
10.1007/s00340-006-2287-x
| null |
quant-ph
| null |
With the reliance in the processing of quantum information on a cold trapped
ion, we analyze the entanglement entropy in the ion-field interaction with pair
cat states. We investigate a long-living entanglement allowing the
instantaneous position of the center-of-mass motion of the ion to be explicitly
time dependent. An analytic solution for the system operators is obtained. We
show that different nonclassical effects arise in the dynamics of the
population inversion, depending on the initial states of the vibrational
motion. We study in detail the entanglement degree and demonstrate how the
input pair cat state is required for initiating the long living entanglement.
This long living entanglement is damp out with an increase in the number
difference $q$. Owing to the properties of entanglement measures, the results
are checked using another entanglement measure (high order linear entropy).
|
[
{
"version": "v1",
"created": "Mon, 27 Mar 2006 17:04:42 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Abdel-Aty",
"Mahmoud",
""
]
] |
quant-ph/0603250
|
Stefano Zippilli
|
Stefano Zippilli, Giovanna Morigi, Wolfgang P. Schleich
|
Ground state cooling in a bad cavity
|
6 pages, 5 figures; J. Mod. Opt. (2007)
|
J. Mod. Opt. 54, 1595 (2007).
|
10.1080/09500340600736843
| null |
quant-ph
| null |
We study the mechanical effects of light on an atom trapped in a harmonic
potential when an atomic dipole transition is driven by a laser and it is
strongly coupled to a mode of an optical resonator. We investigate the cooling
dynamics in the bad cavity limit, focussing on the case in which the effective
transition linewidth is smaller than the trap frequency, hence when sideband
cooling could be implemented. We show that quantum correlations between the
mechanical actions of laser and cavity field can lead to an enhancement of the
cooling efficiency with respect to sideband cooling. Such interference effects
are found when the resonator losses prevail over spontaneous decay and over the
rates of the coherent processes characterizing the dynamics.
|
[
{
"version": "v1",
"created": "Mon, 27 Mar 2006 17:46:30 GMT"
}
] | 2007-09-05T00:00:00 |
[
[
"Zippilli",
"Stefano",
""
],
[
"Morigi",
"Giovanna",
""
],
[
"Schleich",
"Wolfgang P.",
""
]
] |
quant-ph/0603251
|
Alexander Russell
|
Gorjan Alagic and Cristopher Moore and Alexander Russell
|
Quantum Algorithms for Simon's Problem Over General Groups
| null |
Proc. 18th ACM-SIAM Symposium on Discrete Algorithms (SODA) 2007
| null | null |
quant-ph
| null |
Daniel Simon's 1994 discovery of an efficient quantum algorithm for solving
the hidden subgroup problem (HSP) over Z_2^n provided one of the first
algebraic problems for which quantum computers are exponentially faster than
their classical counterparts. In this paper, we study the generalization of
Simon's problem to arbitrary groups. Fixing a finite group G, this is the
problem of recovering an involution m = (m_1, ..., m_n) in G^n from an oracle f
with the property that f(x) = f(xy) iff y equals m or the identity. In the
current parlance, this is the hidden subgroup problem (HSP) over groups of the
form G^n, where G is a nonabelian group of constant size, and where the hidden
subgroup is either trivial or has order two. Although groups of the form G^n
have a simple product structure, they share important representation-theoretic
properties with the symmetric groups S_n, where a solution to the HSP would
yield a quantum algorithm for Graph Isomorphism. In particular, solving their
HSP with the so-called ``standard method'' requires highly entangled
measurements on the tensor product of many coset states. Here we give quantum
algorithms with time complexity 2^O(sqrt(n log n)) that recover hidden
involutions m = (m_1, ..., m_n) in G^n where, as in Simon's problem, each m_i
is either the identity or the conjugate of a known element k, and there is a
character X of G for which X(k) = -X(1)$. Our approach combines the general
idea behind Kuperberg's sieve for dihedral groups with the ``missing harmonic''
approach of Moore and Russell. These are the first nontrivial hidden subgroup
algorithms for group families that require highly entangled multiregister
Fourier sampling.
|
[
{
"version": "v1",
"created": "Tue, 28 Mar 2006 18:04:29 GMT"
},
{
"version": "v2",
"created": "Fri, 26 Jan 2007 01:14:44 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Alagic",
"Gorjan",
""
],
[
"Moore",
"Cristopher",
""
],
[
"Russell",
"Alexander",
""
]
] |
quant-ph/0603252
|
Emanuel Knill
|
E. Knill
|
On Protected Realizations of Quantum Information
|
17 pages
| null |
10.1103/PhysRevA.74.042301
| null |
quant-ph
| null |
There are two complementary approaches to realizing quantum information so
that it is protected from a given set of error operators. Both involve encoding
information by means of subsystems. One is initialization-based error
protection, which involves a quantum operation that is applied before error
events occur. The other is operator quantum error correction, which uses a
recovery operation applied after the errors. Together, the two approaches make
it clear how quantum information can be stored at all stages of a process
involving alternating error and quantum operations. In particular, there is
always a subsystem that faithfully represents the desired quantum information.
We give a definition of faithful realization of quantum information and show
that it always involves subsystems. This justifies the "subsystems principle"
for realizing quantum information. In the presence of errors, one can make use
of noiseless, (initialization) protectable, or error-correcting subsystems. We
give an explicit algorithm for finding optimal noiseless subsystems. Finding
optimal protectable or error-correcting subsystems is in general difficult.
Verifying that a subsystem is error-correcting involves only linear algebra. We
discuss the verification problem for protectable subsystems and reduce it to a
simpler version of the problem of finding error-detecting codes.
|
[
{
"version": "v1",
"created": "Mon, 27 Mar 2006 22:21:32 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Knill",
"E.",
""
]
] |
quant-ph/0603253
|
Luis Manuel Arevalo Aguilar
|
P. C. Garcia Quijas and L. M. Arevalo Aguilar
|
Factorizing the time evolution operator
|
24 pages; added references; one figure changed
|
Phys. Scr. 75 (2007) 185--194
|
10.1088/0031-8949/75/2/012
| null |
quant-ph
| null |
There is a widespread belief in the quantum physical community, and in
textbooks used to teach Quantum Mechanics, that it is a difficult task to apply
the time evolution operator Exp{-itH/h} on an initial wave function. That is to
say, because the hamiltonian operator generally is the sum of two operators,
then it is a difficult task to apply the time evolution operator on an initial
wave function f(x,0), for it implies to apply terms operators like (a+b)^n. A
possible solution of this problem is to factorize the time evolution operator
and then apply successively the individual exponential operator on the initial
wave function. However, the exponential operator does not directly factorize,
i. e. Exp{a+b} is not equal to Exp{a}Exp{b}. In this work we present a useful
procedure for factorizing the time evolution operator when the argument of the
exponential is a sum of two operators, which obey specific commutation
relations. Then, we apply the exponential operator as an evolution operator for
the case of elementary unidimensional potentials, like the particle subject to
a constant force and the harmonic oscillator. Also, we argue about an apparent
paradox concerning the time evolution operator and non-spreading wave packets
addressed previously in the literature.
|
[
{
"version": "v1",
"created": "Tue, 28 Mar 2006 01:37:00 GMT"
},
{
"version": "v2",
"created": "Thu, 1 Jun 2006 17:40:11 GMT"
},
{
"version": "v3",
"created": "Wed, 13 Sep 2006 01:02:46 GMT"
}
] | 2020-11-24T00:00:00 |
[
[
"Quijas",
"P. C. Garcia",
""
],
[
"Aguilar",
"L. M. Arevalo",
""
]
] |
quant-ph/0603254
|
Masahito Hayashi
|
Masahito Hayashi, Bao-Sen Shi, Akihisa Tomita, Keiji Matsumoto,
Yoshiyuki Tsuda, and Yun-Kun Jiang
|
Hypothesis testing for an entangled state produced by spontaneous
parametric down conversion
|
7 figures, 9 pages. This paper is revised for increasing the
readership for experimentalists. Hence, the mathematical part is moved to a
new manuscript quant-ph/0608022
|
Physical Review A, 74, 062321 (2006)
|
10.1103/PhysRevA.74.062321
| null |
quant-ph
| null |
Generation and characterization of entanglement are crucial tasks in quantum
information processing. A hypothesis testing scheme for entanglement has been
formulated. Three designs were proposed to test the entangled photon states
created by the spontaneous parametric down conversion. The time allocations
between the measurement vectors were designed to consider the anisotropic
deviation of the generated photon states from the maximally entangled states.
The designs were evaluated in terms of the p-value based on the observed data.
It has been experimentally demonstrated that the optimal time allocation
between the coincidence and anti-coincidence measurement vectors improves the
entanglement test. A further improvement is also experimentally demonstrated by
optimizing the time allocation between the anti-coincidence vectors. Analysis
on the data obtained in the experiment verified the advantage of the
entanglement test designed by the optimal time allocation.
|
[
{
"version": "v1",
"created": "Tue, 28 Mar 2006 04:48:16 GMT"
},
{
"version": "v2",
"created": "Wed, 2 Aug 2006 10:02:52 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Hayashi",
"Masahito",
""
],
[
"Shi",
"Bao-Sen",
""
],
[
"Tomita",
"Akihisa",
""
],
[
"Matsumoto",
"Keiji",
""
],
[
"Tsuda",
"Yoshiyuki",
""
],
[
"Jiang",
"Yun-Kun",
""
]
] |
quant-ph/0603255
|
Rajiah Simon
|
J. Solomon Ivan, N. Mukunda, and R. Simon
|
Generation of NPT Entanglement from Nonclassical Photon Statistics
|
4 pages
| null | null | null |
quant-ph
| null |
With a product state of the form $\rho_{in} = \rho_a\otimes|0>_b_b< 0|$ as
input, the output two-mode state $\rho_{{\rm out}}$, of the beam splitter is
shown to be NPT whenever the photon number distribution (PND) statistics
$\{p(n_a) \}$ associated with the possibly mixed state $\rho_a$ of the a_mode
is antibunched or otherwise nonclassical, i.e., if $\{p(n_a)\}$ fails to
respect any one of an infinite of classicality conditions.
|
[
{
"version": "v1",
"created": "Tue, 28 Mar 2006 09:53:14 GMT"
},
{
"version": "v2",
"created": "Wed, 5 Apr 2006 10:57:09 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Ivan",
"J. Solomon",
""
],
[
"Mukunda",
"N.",
""
],
[
"Simon",
"R.",
""
]
] |
quant-ph/0603256
|
Ting Yu
|
Ting Yu and J. H. Eberly
|
Quantum Open System Theory: Bipartite Aspects
|
4 pages, 2 figures, revised version
|
Phys. Rev. Lett. 97, 140403 (2006)
|
10.1103/PhysRevLett.97.140403
| null |
quant-ph
| null |
We demonstrate in straightforward calculations that even under ideally weak
noise the relaxation of bipartite open quantum systems contains elements not
previously encountered in quantum noise physics. While additivity of decay
rates is known to be generic for decoherence of a single system, we demonstrate
that it breaks down for bipartite coherence of even the simplest composite
systems.
|
[
{
"version": "v1",
"created": "Tue, 28 Mar 2006 18:12:11 GMT"
},
{
"version": "v2",
"created": "Fri, 1 Sep 2006 21:24:39 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Yu",
"Ting",
""
],
[
"Eberly",
"J. H.",
""
]
] |
quant-ph/0603257
|
Filippo Caruso
|
Filippo Caruso, Vittorio Giovannetti
|
Degradability of Bosonic Gaussian channels
|
7 pages, 1 figure, 1 table (minor editing)
|
Physical Review A 74, 062307 (2006)
|
10.1103/PhysRevA.74.062307
| null |
quant-ph cond-mat.other physics.optics
| null |
The notion of weak-degradability of quantum channels is introduced by
generalizing the degradability definition given by Devetak and Shor. Exploiting
the unitary equivalence with beam-splitter/amplifier channels we then prove
that a large class of one-mode Bosonic Gaussian channels are either weakly
degradable or anti-degradable. In the latter case this implies that their
quantum capacity Q is null. In the former case instead, this allows us to
establish the additivity of the coherent information for those maps which admit
unitary representation with single-mode pure environment.
|
[
{
"version": "v1",
"created": "Tue, 28 Mar 2006 14:36:20 GMT"
},
{
"version": "v2",
"created": "Fri, 21 Jul 2006 16:49:21 GMT"
},
{
"version": "v3",
"created": "Tue, 10 Oct 2006 10:04:53 GMT"
},
{
"version": "v4",
"created": "Fri, 23 Feb 2007 14:41:02 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Caruso",
"Filippo",
""
],
[
"Giovannetti",
"Vittorio",
""
]
] |
quant-ph/0603258
|
Martin Madsen
|
M. J. Madsen, D. L. Moehring, P. Maunz, R. N. Kohn Jr., L.-M. Duan and
C. Monroe
|
Ultrafast Coherent Coupling of Atomic Hyperfine and Photon Frequency
Qubits
|
4 pages, 4 figures
| null | null | null |
quant-ph
| null |
We demonstrate ultrafast coherent coupling between an atomic qubit stored in
a single trapped cadmium ion and a photonic qubit represented by two resolved
frequencies of a photon. Such ultrafast coupling is crucial for entangling
networks of remotely-located trapped ions through photon interference, and is
also a key component for realizing ultrafast quantum gates between
Coulomb-coupled ions.
|
[
{
"version": "v1",
"created": "Tue, 28 Mar 2006 16:46:09 GMT"
},
{
"version": "v2",
"created": "Fri, 7 Apr 2006 17:39:54 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Madsen",
"M. J.",
""
],
[
"Moehring",
"D. L.",
""
],
[
"Maunz",
"P.",
""
],
[
"Kohn",
"R. N.",
"Jr."
],
[
"Duan",
"L. -M.",
""
],
[
"Monroe",
"C.",
""
]
] |
quant-ph/0603259
|
David Latimer
|
D. C. Latimer
|
Comment on ``Symplectic quantization, inequivalent quantum theories, and
Heisenberg's principle of uncertainty''
|
6 pages, updated version
|
Phys. Rev. A 75, 066101 (2007)
|
10.1103/PhysRevA.75.066101
| null |
quant-ph
| null |
In Phys. Rev. A 70, 032104 (2004), M. Montesinos and G. F. Torres del
Castillo consider various symplectic structures on the classical phase space of
the two-dimensional isotropic harmonic oscillator. Using Dirac's quantization
condition, the authors investigate how these alternative symplectic forms
affect this system's quantization. They claim that these symplectic structures
result in mutually inequivalent quantum theories. In fact, we show here that
there exists a unitary map between the two representation spaces so that the
various quantizations are equivalent.
|
[
{
"version": "v1",
"created": "Tue, 28 Mar 2006 20:29:45 GMT"
},
{
"version": "v2",
"created": "Mon, 8 Jan 2007 22:18:39 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Latimer",
"D. C.",
""
]
] |
quant-ph/0603260
|
Michal Horodecki
|
Robert Alicki and Michal Horodecki
|
Can one build a quantum hard drive? A no-go theorem for storing quantum
information in equilibrium systems
|
6 pages, 2 figures
| null | null | null |
quant-ph
| null |
We prove a no-go theorem for storing quantum information in equilibrium
systems. Namely, quantum information cannot be stored in a system with
time-independent Hamiltonian interacting with heat bath of temperature $T>0$
during time that grows with the number of used qubits. We prove it by showing,
that storing quantum information for macroscopic time would imply existence of
perpetuum mobile of the second kind. The general results are illustrated by the
Kitaev model of quantum memory. In contrast, classical information can be
stored in equilibrium states for arbitrary long times. We show how it is
possible via phase-transition type phenomena. Our result shows that there is a
fundamental difference between quantum and classical information in {\it
physical} terms.
|
[
{
"version": "v1",
"created": "Tue, 28 Mar 2006 20:56:37 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Alicki",
"Robert",
""
],
[
"Horodecki",
"Michal",
""
]
] |
quant-ph/0603261
|
Ra\'ul Oscar Vallejos
|
Romulo F. Abreu and Raul O. Vallejos
|
Entangling power of baker's map: Role of symmetries
|
5 pages
| null |
10.1103/PhysRevA.73.052327
| null |
quant-ph
| null |
The quantum baker map possesses two symmetries: a canonical "spatial"
symmetry, and a time-reversal symmetry. We show that, even when these features
are taken into account, the asymptotic entangling power of the baker's map does
not always agree with the predictions of random matrix theory. We have verified
that the dimension of the Hilbert space is the crucial parameter which
determines whether the entangling properties of the baker are universal or not.
For power-of-two dimensions, i.e., qubit systems, an anomalous entangling power
is observed; otherwise the behavior of the baker is consistent with random
matrix theories. We also derive a general formula that relates the asymptotic
entangling power of an arbitrary unitary with properties of its reduced
eigenvectors.
|
[
{
"version": "v1",
"created": "Tue, 28 Mar 2006 20:58:54 GMT"
},
{
"version": "v2",
"created": "Tue, 28 Mar 2006 21:06:07 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Abreu",
"Romulo F.",
""
],
[
"Vallejos",
"Raul O.",
""
]
] |
quant-ph/0603262
|
Graeme Smith
|
Joseph M. Renes and Graeme Smith
|
Noisy Preprocessing and the Distillation of Private States
|
4 pages, to appear in Physical Review Letters. Extensively rewritten,
with a more detailed discussion of coherent --> iid reduction
|
Phys. Rev. Lett. 98, 020502 (2007)
|
10.1103/PhysRevLett.98.020502
| null |
quant-ph
| null |
We provide a simple security proof for prepare & measure quantum key
distribution protocols employing noisy processing and one-way postprocessing of
the key. This is achieved by showing that the security of such a protocol is
equivalent to that of an associated key distribution protocol in which, instead
of the usual maximally-entangled states, a more general {\em private state} is
distilled. Besides a more general target state, the usual entanglement
distillation tools are employed (in particular, Calderbank-Shor-Steane
(CSS)-like codes), with the crucial difference that noisy processing allows
some phase errors to be left uncorrected without compromising the privacy of
the key.
|
[
{
"version": "v1",
"created": "Tue, 28 Mar 2006 21:24:22 GMT"
},
{
"version": "v2",
"created": "Thu, 14 Dec 2006 21:38:05 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Renes",
"Joseph M.",
""
],
[
"Smith",
"Graeme",
""
]
] |
quant-ph/0603263
|
Ranjith Nair
|
Ranjith Nair, Horace P. Yuen, Eric Corndorf, Takami Eguchi, and Prem
Kumar
|
Quantum Noise Randomized Ciphers
|
Accepted for publication in Phys. Rev. A; Discussion augmented and
re-organized; Section 5 contains a detailed response to 'T. Nishioka, T.
Hasegawa, H. Ishizuka, K. Imafuku, H. Imai: Phys. Lett. A 327 (2004) 28-32
/quant-ph/0310168' & 'T. Nishioka, T. Hasegawa, H. Ishizuka, K. Imafuku, H.
Imai: Phys. Lett. A 346 (2005) 7'
| null |
10.1103/PhysRevA.74.052309
| null |
quant-ph
| null |
We review the notion of a classical random cipher and its advantages. We
sharpen the usual description of random ciphers to a particular mathematical
characterization suggested by the salient feature responsible for their
increased security. We describe a concrete system known as AlphaEta and show
that it is equivalent to a random cipher in which the required randomization is
effected by coherent-state quantum noise. We describe the currently known
security features of AlphaEta and similar systems, including lower bounds on
the unicity distances against ciphertext-only and known-plaintext attacks. We
show how AlphaEta used in conjunction with any standard stream cipher such as
AES (Advanced Encryption Standard) provides an additional, qualitatively
different layer of security from physical encryption against known-plaintext
attacks on the key. We refute some claims in the literature that AlphaEta is
equivalent to a non-random stream cipher.
|
[
{
"version": "v1",
"created": "Wed, 29 Mar 2006 00:01:24 GMT"
},
{
"version": "v2",
"created": "Thu, 30 Mar 2006 01:08:18 GMT"
},
{
"version": "v3",
"created": "Tue, 9 May 2006 21:13:06 GMT"
},
{
"version": "v4",
"created": "Wed, 17 May 2006 23:46:25 GMT"
},
{
"version": "v5",
"created": "Wed, 27 Sep 2006 21:28:42 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Nair",
"Ranjith",
""
],
[
"Yuen",
"Horace P.",
""
],
[
"Corndorf",
"Eric",
""
],
[
"Eguchi",
"Takami",
""
],
[
"Kumar",
"Prem",
""
]
] |
quant-ph/0603264
|
Horace P. Yuen
|
Horace P. Yuen
|
Direct Use of Secret Key in Quantum Cryptography
|
To be submitted to Phys. Rev. Lett
| null | null | null |
quant-ph
| null |
For single-photon quantum key generation between two users, it is shown that
the use of a shared secret key extended via a pseudo-random number generator
may simultaneously enhance the security and efficiency of the cryptosystem.
This effect arises from the intrinsic performance difference between quantum
detectors with versus without knowledge of the key, a purely quantum effect and
a new principle for key generation. No intrusion level estimation is needed and
the method is directly applicable to realistic systems with imperfections.
Quantum direct encryption is also made possible by such use of a secret key.
|
[
{
"version": "v1",
"created": "Wed, 29 Mar 2006 00:10:32 GMT"
},
{
"version": "v2",
"created": "Tue, 9 May 2006 21:19:27 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Yuen",
"Horace P.",
""
]
] |
quant-ph/0603265
|
Lars Bojer Madsen
|
Lars Bojer Madsen, Klaus Molmer
|
Entanglement between remote continuous variable quantum systems: effects
of transmission loss
|
7 pages, 4 figures
| null | null | null |
quant-ph
| null |
We study the effects of losses on the entanglement created between two
separate atomic gases by optical probing and homodyne detection of the
transmitted light. The system is well-described in the Gaussian state
formulation. Analytical results quantifying the degree of entanglement between
the two gases are derived and compared with the entanglement in a pair of light
pulses generated by an EPR source. For low (high) transmission losses the
highest degree of entanglement is obtained by probing with squeezed
(antisqueezed) light. In an asymmetric setup where light is only sent one way
through the atomic samples, we find that the logarithmic negativity of
entanglement attains a constant value $-\log_2(N)$ with $N=1/3$ irrespectively
of the loss along the transmission line.
|
[
{
"version": "v1",
"created": "Wed, 29 Mar 2006 08:00:24 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Madsen",
"Lars Bojer",
""
],
[
"Molmer",
"Klaus",
""
]
] |
quant-ph/0603266
|
Niel de Beaudrap
|
Niel de Beaudrap, Vincent Danos, and Elham Kashefi
|
Phase map decompositions for unitaries
|
17 pages: earlier version submitted to ICALP 2006
| null | null | null |
quant-ph
| null |
We propose a universal decomposition of unitary maps over a tensorial power
of C^2, introducing the key concept of "phase maps", and investigate how this
decomposition can be used to implement unitary maps directly in the
measurement-based model for quantum computing. Specifically, we show how to
extract from such a decomposition a matching entangled graph state (with
inputs), and a set of measurements angles, when there is one. Next, we check
whether the obtained graph state verifies a "flow" condition, which guarantees
an execution order such that the dependent measurements and corrections of the
pattern yield deterministic results. Using a graph theoretic characterization
of flows, we can determine whether a flow can be constructed for a graph state
in polynomial time. This approach yields an algorithmic procedure which, when
it succeeds, may produce an efficient pattern for a given unitary.
|
[
{
"version": "v1",
"created": "Wed, 29 Mar 2006 19:05:05 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"de Beaudrap",
"Niel",
""
],
[
"Danos",
"Vincent",
""
],
[
"Kashefi",
"Elham",
""
]
] |
quant-ph/0603267
|
Giuseppe Liberti
|
G. Liberti, F. Plastina and F. Piperno
|
Scaling behavior in the adiabatic Dicke Model
|
4 pages, 3 figures
|
Phys. Rev. A 74, 022324 (2006)
|
10.1103/PhysRevA.74.022324
| null |
quant-ph
| null |
We analyze the quantum phase transition for a set of $N$-two level systems
interacting with a bosonic mode in the adiabatic regime. Through the
Born-Oppenheimer approximation, we obtain the finite-size scaling expansion for
many physical observables and, in particular, for the entanglement content of
the system.
|
[
{
"version": "v1",
"created": "Wed, 29 Mar 2006 09:41:31 GMT"
},
{
"version": "v2",
"created": "Mon, 15 May 2006 08:14:23 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Liberti",
"G.",
""
],
[
"Plastina",
"F.",
""
],
[
"Piperno",
"F.",
""
]
] |
quant-ph/0603268
|
Joshua Nunn
|
J Nunn, I A Walmsley, M G Raymer, K Surmacz, F C Waldermann, Z Wang
and D Jaksch
|
Modematching an optical quantum memory
|
17 pages, 4 figures. Brief section added treating the transverse
spatial structure of the memory interaction. Some references added. A few
typos fixed
| null |
10.1103/PhysRevA.75.011401
| null |
quant-ph
| null |
We analyse the off-resonant Raman interaction of a single broadband photon,
copropagating with a classical `control' pulse, with an atomic ensemble. It is
shown that the classical electrodynamical structure of the interaction
guarantees canonical evolution of the quantum mechanical field operators. This
allows the interaction to be decomposed as a beamsplitter transformation
between optical and material excitations on a mode-by-mode basis. A single,
dominant modefunction describes the dynamics for arbitrary control pulse
shapes.
Complete transfer of the quantum state of the incident photon to a collective
dark state within the ensemble can be achieved by shaping the control pulse so
as to match the dominant mode to the temporal mode of the photon. Readout of
the material excitation, back to the optical field, is considered in the
context of the symmetry connecting the input and output modes. Finally, we show
that the transverse spatial structure of the interaction is characterised by
the same mode decomposition.
|
[
{
"version": "v1",
"created": "Wed, 29 Mar 2006 11:39:14 GMT"
},
{
"version": "v2",
"created": "Wed, 26 Apr 2006 14:09:49 GMT"
}
] | 2013-05-29T00:00:00 |
[
[
"Nunn",
"J",
""
],
[
"Walmsley",
"I A",
""
],
[
"Raymer",
"M G",
""
],
[
"Surmacz",
"K",
""
],
[
"Waldermann",
"F C",
""
],
[
"Wang",
"Z",
""
],
[
"Jaksch",
"D",
""
]
] |
quant-ph/0603269
|
Paul M. Alsing
|
P.M. Alsing, I. Fuentes-Schuller, R.B. Mann and T.E. Tessier
|
Entanglement of Dirac fields in non-inertial frames
|
15 pages, with 8 figures (Mar 2006); accepted to Physical Review A,
July 2006 - slightly revised
| null |
10.1103/PhysRevA.74.032326
| null |
quant-ph gr-qc hep-th
| null |
We analyze the entanglement between two modes of a free Dirac field as seen
by two relatively accelerated parties. The entanglement is degraded by the
Unruh effect and asymptotically reaches a non-vanishing minimum value in the
infinite acceleration limit. This means that the state always remains entangled
to a degree and can be used in quantum information tasks, such as
teleportation, between parties in relative uniform acceleration. We analyze our
results from the point of view afforded by the phenomenon of entanglement
sharing and in terms of recent results in the area of multi-qubit
complementarity.
|
[
{
"version": "v1",
"created": "Wed, 29 Mar 2006 20:28:10 GMT"
},
{
"version": "v2",
"created": "Wed, 12 Jul 2006 06:44:51 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Alsing",
"P. M.",
""
],
[
"Fuentes-Schuller",
"I.",
""
],
[
"Mann",
"R. B.",
""
],
[
"Tessier",
"T. E.",
""
]
] |
quant-ph/0603270
|
Tobias Moroder
|
Tobias Moroder, Marcos Curty, Norbert L\"utkenhaus
|
One-way quantum key distribution: Simple upper bound on the secret key
rate
|
11 pages, 1 figure
|
Phys. Rev. A 74, 052301 (2006)
|
10.1103/PhysRevA.74.052301
| null |
quant-ph
| null |
We present a simple method to obtain an upper bound on the achievable secret
key rate in quantum key distribution (QKD) protocols that use only
unidirectional classical communication during the public-discussion phase. This
method is based on a necessary precondition for one-way secret key
distillation; the legitimate users need to prove that there exists no quantum
state having a symmetric extension that is compatible with the available
measurements results. The main advantage of the obtained upper bound is that it
can be formulated as a semidefinite program, which can be efficiently solved.
We illustrate our results by analysing two well-known qubit-based QKD
protocols: the four-state protocol and the six-state protocol. Recent results
by Renner et al., Phys. Rev. A 72, 012332 (2005), also show that the given
precondition is only necessary but not sufficient for unidirectional secret key
distillation.
|
[
{
"version": "v1",
"created": "Wed, 29 Mar 2006 22:24:22 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Moroder",
"Tobias",
""
],
[
"Curty",
"Marcos",
""
],
[
"Lütkenhaus",
"Norbert",
""
]
] |
quant-ph/0603271
|
Stefan Lorenz
|
S. Lorenz, J. Rigas, M. Heid, U.L. Andersen, N. L\"utkenhaus, G.
Leuchs
|
Witnessing effective entanglement in a continuous variable
prepare&measure setup and application to a QKD scheme using postselection
|
12 pages, 12 figures, 2 tables
| null |
10.1103/PhysRevA.74.042326
| null |
quant-ph
| null |
We report an experimental demonstration of effective entanglement in a
prepare&measure type of quantum key distribution protocol. Coherent
polarization states and heterodyne measurement to characterize the transmitted
quantum states are used, thus enabling us to reconstruct directly their
Q-function. By evaluating the excess noise of the states, we experimentally
demonstrate that they fulfill a non-separability criterion previously presented
by Rigas et al. [J. Rigas, O. G\"uhne, N. L\"utkenhaus, Phys. Rev. A 73, 012341
(2006)]. For a restricted eavesdropping scenario we predict key rates using
postselection of the heterodyne measurement results.
|
[
{
"version": "v1",
"created": "Thu, 30 Mar 2006 08:33:09 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Lorenz",
"S.",
""
],
[
"Rigas",
"J.",
""
],
[
"Heid",
"M.",
""
],
[
"Andersen",
"U. L.",
""
],
[
"Lütkenhaus",
"N.",
""
],
[
"Leuchs",
"G.",
""
]
] |
quant-ph/0603272
|
Omar Mustafa
|
Omar Mustafa and S. Habib Mazharimousavi
|
Non-Hermitian d-dimensional Hamiltonians with position dependent mass
and their $\eta$-pseudo-Hermiticity generators
|
10 pages, no figures, to appear in the Czech. J. Phys
|
Czech.J.Phys., volume 56, pages 967-976 (2006)
|
10.1007/s10582-006-0392-z
| null |
quant-ph
| null |
A class of non-Hermitian d-dimensional Hamiltonias with position dependent
mass and their $\eta$-pseudo-Hermiticity generators is presented. Illustrative
examples are given in 1D, 2D, and 3D for different position dependent mass
settings.
|
[
{
"version": "v1",
"created": "Thu, 30 Mar 2006 08:35:33 GMT"
},
{
"version": "v2",
"created": "Tue, 2 May 2006 09:37:08 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Mustafa",
"Omar",
""
],
[
"Mazharimousavi",
"S. Habib",
""
]
] |
quant-ph/0603273
|
Jonathan Home
|
J. P. Home, M. J. McDonnell, D. M. Lucas, G. Imreh, B. C. Keitch, D.
J. Szwer, N. R. Thomas, S. C. Webster, D. N. Stacey and A. M. Steane
|
Deterministic entanglement and tomography of ion spin qubits
|
3 figures, 4 pages, footnotes fixed
|
New J. Phys. 8 (2006) 188.
|
10.1088/1367-2630/8/9/188
| null |
quant-ph
| null |
We have implemented a universal quantum logic gate between qubits stored in
the spin state of a pair of trapped calcium 40 ions. An initial product state
was driven to a maximally entangled state deterministically, with 83% fidelity.
We present a general approach to quantum state tomography which achieves good
robustness to experimental noise and drift, and use it to measure the spin
state of the ions. We find the entanglement of formation is 0.54.
|
[
{
"version": "v1",
"created": "Thu, 30 Mar 2006 10:00:45 GMT"
},
{
"version": "v2",
"created": "Fri, 31 Mar 2006 10:00:34 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Home",
"J. P.",
""
],
[
"McDonnell",
"M. J.",
""
],
[
"Lucas",
"D. M.",
""
],
[
"Imreh",
"G.",
""
],
[
"Keitch",
"B. C.",
""
],
[
"Szwer",
"D. J.",
""
],
[
"Thomas",
"N. R.",
""
],
[
"Webster",
"S. C.",
""
],
[
"Stacey",
"D. N.",
""
],
[
"Steane",
"A. M.",
""
]
] |
quant-ph/0603274
|
Marie Lalire
|
Marie Lalire
|
Relations among quantum processes: bisimilarity and congruence
|
23 pages, accepted for publication in MSCS
| null | null | null |
quant-ph
| null |
Full formal descriptions of algorithms making use of quantum principles must
take into account both quantum and classical computing components, as well as
communications between these components. Moreover, to model concurrent and
distributed quantum computations and quantum communication protocols,
communications over quantum channels which move qubits physically from one
place to another must also be taken into account.
Inspired by classical process algebras, which provide a framework for
modeling cooperating computations, a process algebraic notation is defined.
This notation provides a homogeneous style to formal descriptions of concurrent
and distributed computations comprising both quantum and classical parts. Based
upon an operational semantics which makes sure that quantum objects, operations
and communications operate according to the postulates of quantum mechanics, an
equivalence is defined among process states considered as having the same
behavior. This equivalence is a probabilistic branching bisimulation. From this
relation, an equivalence on processes is defined. However, it is not a
congruence because it is not preserved by parallel composition.
|
[
{
"version": "v1",
"created": "Thu, 30 Mar 2006 11:58:17 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Lalire",
"Marie",
""
]
] |
quant-ph/0603275
|
Rosario Lo Franco
|
R. Lo Franco, G. Compagno, A. Messina, and A. Napoli
|
Generation of Entangled Two-Photons Binomial States in Two Spatially
Separate Cavities
|
8 pages, 2 figures, submitted to "Open Systems & Information
Dynamics"
|
Open Systems & Information Dynamics 13, 463 (2006)
| null | null |
quant-ph
| null |
We propose a conditional scheme to generate entangled two-photons generalized
binomial states inside two separate single-mode high-Q cavities. This scheme
requires that the two cavities are initially prepared in entangled one-photon
generalized binomial states and exploits the passage of two appropriately
prepared two-level atoms one in each cavity. The measurement of the ground
state of both atoms is finally required when they exit the cavities. We also
give a brief evaluation of the experimental feasibility of the scheme.
|
[
{
"version": "v1",
"created": "Thu, 30 Mar 2006 14:06:04 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Franco",
"R. Lo",
""
],
[
"Compagno",
"G.",
""
],
[
"Messina",
"A.",
""
],
[
"Napoli",
"A.",
""
]
] |
quant-ph/0603276
|
Lajos Di\'osi
|
Andr\'as Bodor, Lajos Di\'osi
|
On Conserved Current in Markovian Open Quantum Systems
|
3 pages
|
Phys. Rev. A73 (2006) 064101-(3)
|
10.1103/PhysRevA.73.064101
| null |
quant-ph cond-mat.other
| null |
We reexamine the markovian approximation of local current in open quantum
systems, discussed recently by Gebauer and Car. Our derivation is more
transparent, the proof of current conservation becomes explicit and easy.
|
[
{
"version": "v1",
"created": "Thu, 30 Mar 2006 14:43:07 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Bodor",
"András",
""
],
[
"Diósi",
"Lajos",
""
]
] |
quant-ph/0603277
|
Alberto C. de la Torre
|
Alberto C. de la Torre
|
Observables have no value: a no-go theorem for position and momentum
observables
|
6 pages, 1 Latex figure small corrections, refference and comments
added
|
Found. of Phys. 37, 1243-1252 (2007)
|
10.1007/s10701-007-9148-2
| null |
quant-ph
| null |
A very simple illustration of the Bell-Kochen-Specker contradiction is
presented using continuous observables in infinite dimensional Hilbert space.
It is shown that the assumption of the \emph{existence} of putative values for
position and momentum observables for one single particle is incompatible with
quantum mechanics.
|
[
{
"version": "v1",
"created": "Thu, 30 Mar 2006 20:16:27 GMT"
},
{
"version": "v2",
"created": "Tue, 16 May 2006 18:36:20 GMT"
},
{
"version": "v3",
"created": "Mon, 9 Oct 2006 21:15:02 GMT"
}
] | 2011-11-09T00:00:00 |
[
[
"de la Torre",
"Alberto C.",
""
]
] |
quant-ph/0603278
|
Rahul Jain
|
Rahul Jain (U. Waterloo) and Ashwin Nayak (U. Waterloo and Perimeter)
|
Accessible versus Holevo Information for a Binary Random Variable
|
ver 1, 6 pages, no figure; ver 2, 7 pages, no figure; ver 3, 11
pages, 3 figures
| null | null | null |
quant-ph
| null |
The accessible information acc(E) of an ensemble E is the maximum mutual
information between a random variable encoded into quantum states, and the
probabilistic outcome of a quantum measurement of the encoding. Accessible
information is extremely difficult to characterize analytically; even bounds on
it are hard to place. The celebrated Holevo bound states that accessible
information cannot exceed chi(E), the quantum mutual information between the
random variable and its encoding. However, for general ensembles, the gap
between the acc(E) and chi(E) may be arbitrarily large.
We consider the special case of a binary random variable, which often serves
as a stepping stone towards other results in information theory and
communication complexity. We give explicit lower bounds on the the accessible
information acc(E) of an ensemble E = {(p, rho_0), (1-p, rho_1)}, with 0 <= p
<= 1, as functions of p and chi(E). The bounds are incomparable in the sense
that they surpass each other in different parameter regimes.
Our bounds arise by measuring the ensemble according to a complete orthogonal
measurement that preserves the fidelity of the states rho_0,rho_1. As an
intermediate step, therefore, we give new relations between the two quantities
acc(E), chi(E) and the fidelity B(rho_0,rho_1).
|
[
{
"version": "v1",
"created": "Thu, 30 Mar 2006 17:50:00 GMT"
},
{
"version": "v2",
"created": "Sat, 15 Jul 2006 20:06:24 GMT"
},
{
"version": "v3",
"created": "Sat, 22 Dec 2007 16:50:45 GMT"
},
{
"version": "v4",
"created": "Sat, 29 Dec 2007 12:55:52 GMT"
}
] | 2007-12-29T00:00:00 |
[
[
"Jain",
"Rahul",
"",
"U. Waterloo"
],
[
"Nayak",
"Ashwin",
"",
"U. Waterloo and Perimeter"
]
] |
quant-ph/0603279
|
Kishore Kapale
|
K. T. Kapale
|
Polarization preserving quantum nondemolition photodetector
| null | null |
10.1080/09500340600753822
| null |
quant-ph
| null |
A polarization preserving quantum nondemolition photodetector is proposed
based on nonlinearities obtainable through quantum coherence effects. An atomic
level scheme is devised such that in the presence of strong linearly polarized
drive field a coherent weak probe field acquires a phase proportional to the
number of photons in the signal mode immaterial of its polarization state. It
is also shown that the unavoidable phase-kicks resulting due to the measurement
process are insensitive to the polarization state of the incoming signal
photon. It is envisioned that such a device would have tremendous applicability
in photonic quantum information proposals where quantum information in the
polarization qubit is to be protected.
|
[
{
"version": "v1",
"created": "Thu, 30 Mar 2006 23:01:31 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Kapale",
"K. T.",
""
]
] |
quant-ph/0603280
|
Joel F. Corney
|
J. F. Corney, P. D. Drummond, J. Heersink, V. Josse, G. Leuchs and U.
L. Andersen
|
Many-body quantum dynamics of polarisation squeezing in optical fibre
|
4 pages, 4 figures
| null |
10.1103/PhysRevLett.97.023606
| null |
quant-ph
| null |
We report new experiments that test quantum dynamical predictions of
polarization squeezing for ultrashort photonic pulses in a birefringent fibre,
including all relevant dissipative effects. This exponentially complex
many-body problem is solved by means of a stochastic phase-space method. The
squeezing is calculated and compared to experimental data, resulting in
excellent quantitative agreement. From the simulations, we identify the
physical limits to quantum noise reduction in optical fibres. The research
represents a significant experimental test of first-principles time-domain
quantum dynamics in a one-dimensional interacting Bose gas coupled to
dissipative reservoirs.
|
[
{
"version": "v1",
"created": "Thu, 30 Mar 2006 23:22:09 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Corney",
"J. F.",
""
],
[
"Drummond",
"P. D.",
""
],
[
"Heersink",
"J.",
""
],
[
"Josse",
"V.",
""
],
[
"Leuchs",
"G.",
""
],
[
"Andersen",
"U. L.",
""
]
] |
quant-ph/0603281
|
Paolo Facchi
|
P. Facchi, G. Florio, S. Pascazio
|
Probability density function characterization of multipartite
entanglement
|
7 pages, 2 figures; published version; title changed; further
explanations and comparison with several measures of multipartite
entanglement added
|
Physical Review A 74, 042331 (2006)
|
10.1103/PhysRevA.74.042331
| null |
quant-ph
| null |
We propose a method to characterize and quantify multipartite entanglement
for pure states. The method hinges upon the study of the probability density
function of bipartite entanglement and is tested on an ensemble of qubits in a
variety of situations. This characterization is also compared to several
measures of multipartite entanglement.
|
[
{
"version": "v1",
"created": "Fri, 31 Mar 2006 09:30:09 GMT"
},
{
"version": "v2",
"created": "Wed, 3 Jan 2007 09:26:25 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Facchi",
"P.",
""
],
[
"Florio",
"G.",
""
],
[
"Pascazio",
"S.",
""
]
] |
quant-ph/0603282
|
A. V. Kuzmin
|
V.I. Kuvshinov, A.V. Kuzmin
|
Decoherence induced by squeezing control errors in optical and ion trap
holonomic quantum computations II
|
The sequel to quant-ph/0601099
|
Phys. Rev. A 73, 052305 (2006)
|
10.1103/PhysRevA.73.052305
| null |
quant-ph
| null |
We study decoherence induced by stochastic squeezing control errors
considering the particular implementation of Hadamard gate on optical and ion
trap holonomic quantum computers. We analytically obtain both the purity of the
final state and the fidelity for Hadamard gate when the control noise is
modeled by Ornstein-Uhlenbeck stochastic process. We demonstrate the purity and
the fidelity oscillations depending on the choice of the initial superimposed
state. We derive a linear formulae connecting the gate fidelity and the purity
of the final state.
|
[
{
"version": "v1",
"created": "Fri, 31 Mar 2006 12:33:51 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Kuvshinov",
"V. I.",
""
],
[
"Kuzmin",
"A. V.",
""
]
] |
quant-ph/0603283
|
Lieven Clarisse
|
Lieven Clarisse
|
A (5,5) and (6,6) PPT edge state
|
5 pages, comments welcome
|
Physics Letters A 359 (2006) 603-607
|
10.1016/j.physleta.2006.07.045
| null |
quant-ph
| null |
Entangled states with a positive partial transpose (PPTES) have interest both
in quantum information and in the theory of positive maps. In $3\otimes 3$
there is a conjecture by Sanpera, Bru{\ss} and Lewenstein [PRA, 63, 050301]
that all PPTES have Schmidt number two (or equivalently that every 2-positive
map between $3\times 3$ matrices is decomposable). In order to prove or
disprove the conjecture it is sufficient to look at edge PPTES. Here the rank m
of the PPTES and the rank n of its partial transpose seem to play an important
role. Until recently all known examples of edge PPTES had ranks (4,4) or (6,7).
In a recent paper Ha and Kye [quant-ph/0509079] managed to find edge PPTES for
all ranks except (5,5) and (6,6). Here we complement their work and present
edge PPTES with those ranks.
|
[
{
"version": "v1",
"created": "Fri, 31 Mar 2006 15:48:24 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Clarisse",
"Lieven",
""
]
] |
quant-ph/0603284
|
Alexei Ourjoumtsev
|
Alexei Ourjoumtsev, Rosa Tualle-Brouri and Philippe Grangier
|
Quantum homodyne tomography of a two-photon Fock state
|
4 pages, 6 figures Revised version : corrected typo and references
|
Phys. Rev. Lett. 96, 213601 (2006)
|
10.1103/PhysRevLett.96.213601
| null |
quant-ph
| null |
We present a continuous-variable experimental analysis of a two-photon Fock
state of free-propagating light. This state is obtained from a pulsed
non-degenerate parametric amplifier, which produces two intensity-correlated
twin beams. Counting two photons in one beam projects the other beam in the
desired two-photon Fock state, which is analyzed by using a pulsed homodyne
detection. The Wigner function of the measured state is clearly negative. We
developed a detailed analytic model which allows a fast and efficient analysis
of the experimental results.
|
[
{
"version": "v1",
"created": "Fri, 31 Mar 2006 16:43:52 GMT"
},
{
"version": "v2",
"created": "Mon, 17 Jul 2006 07:52:31 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Ourjoumtsev",
"Alexei",
""
],
[
"Tualle-Brouri",
"Rosa",
""
],
[
"Grangier",
"Philippe",
""
]
] |
quant-ph/0603285
|
L. M. Duan
|
L.-M. Duan, M. J. Madsen, D. L. Moehring, P. Maunz, R. N. Kohn Jr.,
and C. Monroe
|
Probabilistic Quantum Gates between Remote Atoms through Interference of
Optical Frequency Qubits
| null | null |
10.1103/PhysRevA.73.062324
| null |
quant-ph
| null |
We propose a scheme to perform probabilistic quantum gates on remote trapped
atom qubits through interference of optical frequency qubits. The method does
not require localization of the atoms to the Lamb-Dicke limit, and is not
sensitive to interferometer phase instabilities. Such probabilistic gates can
be used for scalable quantum computation.
|
[
{
"version": "v1",
"created": "Fri, 31 Mar 2006 16:20:02 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Duan",
"L. -M.",
""
],
[
"Madsen",
"M. J.",
""
],
[
"Moehring",
"D. L.",
""
],
[
"Maunz",
"P.",
""
],
[
"Kohn",
"R. N.",
"Jr."
],
[
"Monroe",
"C.",
""
]
] |
quant-ph/0603286
|
David Daems
|
E. Karpov, D. Daems and N. J. Cerf
|
Entanglement enhanced classical capacity of quantum communication
channels with correlated noise in arbitrary dimensions
|
10 pages, 5 figures
|
Phys. Rev. A 74, 032320 (2006)
|
10.1103/PhysRevA.74.032320
| null |
quant-ph
| null |
We study the capacity of d-dimensional quantum channels with memory modeled
by correlated noise. We show that, in agreement with previous results on Pauli
qubit channels, there are situations where maximally entangled input states
achieve higher values of mutual information than product states. Moreover, a
strong dependence of this effect on the nature of the noise correlations as
well as on the parity of the space dimension is found. We conjecture that when
entanglement gives an advantage in terms of mutual information, maximally
entangled states saturate the channel capacity.
|
[
{
"version": "v1",
"created": "Fri, 31 Mar 2006 18:25:51 GMT"
},
{
"version": "v2",
"created": "Thu, 28 Dec 2006 18:07:17 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Karpov",
"E.",
""
],
[
"Daems",
"D.",
""
],
[
"Cerf",
"N. J.",
""
]
] |
quant-ph/0604001
|
Dmitri Maslov
|
D. Maslov, G. W. Dueck, D. M. Miller, and C. Negrevergne
|
Quantum Circuit Simplification and Level Compaction
|
13 pages, 6 figures. New author, improved presentation, more results
|
IEEE Transactions on Computer-Aided Design of Integrated Circuits
and Systems, 27(3):436-444, March 2008
|
10.1109/TCAD.2007.911334
| null |
quant-ph
| null |
Quantum circuits are time dependent diagrams describing the process of
quantum computation. Usually, a quantum algorithm must be mapped into a quantum
circuit. Optimal synthesis of quantum circuits is intractable and heuristic
methods must be employed. With the use of heuristics, the optimality of
circuits is no longer guaranteed. In this paper, we consider a local
optimization technique based on templates to simplify and reduce the depth of
non-optimal quantum circuits. We present and analyze templates in the general
case, and provide particular details for the circuits composed of NOT, CNOT and
controlled-sqrt-of-NOT gates. We apply templates to optimize various common
circuits implementing multiple control Toffoli gates and quantum Boolean
arithmetic circuits. We also show how templates can be used to compact the
number of levels of a quantum circuit. The runtime of our implementation is
small while the reduction in number of quantum gates and number of levels is
significant.
|
[
{
"version": "v1",
"created": "Sat, 1 Apr 2006 01:09:47 GMT"
},
{
"version": "v2",
"created": "Wed, 27 Feb 2008 17:33:46 GMT"
}
] | 2008-02-27T00:00:00 |
[
[
"Maslov",
"D.",
""
],
[
"Dueck",
"G. W.",
""
],
[
"Miller",
"D. M.",
""
],
[
"Negrevergne",
"C.",
""
]
] |
quant-ph/0604002
|
Maria Bondani
|
Maria Bondani, Alessia Allevi, Eleonora Gevinti, Andrea Agliati,
Alessandra Andreoni
|
3D phase-matching conditions for the generation of entangled triplets by
chi(2) interlinked interactions
|
6 pages, 3 figures, 1 movie (extension of fig. 2)
| null |
10.1364/OE.14.009838
| null |
quant-ph
| null |
An analytical calculation of the interaction geometry of two interlinked
second-order nonlinear processes fulfilling phase-matching conditions is
presented. The method is developed for type-I uniaxial crystals and gives the
positions on a screen beyond the crystal of the entangled triplets generated by
the interactions. The analytical results are compared to experiments realized
in the macroscopic regime. Preliminary tests to identify the triplets are also
performed based on intensity correlations.
|
[
{
"version": "v1",
"created": "Sat, 1 Apr 2006 12:31:12 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Bondani",
"Maria",
""
],
[
"Allevi",
"Alessia",
""
],
[
"Gevinti",
"Eleonora",
""
],
[
"Agliati",
"Andrea",
""
],
[
"Andreoni",
"Alessandra",
""
]
] |
quant-ph/0604003
|
Gia Giorgadze
|
G. Giorgadze and Z. Melikishvili
|
Atom-Photon Interactions with Respect to Quantum Computation:
Three-Level Atom in Two-Mode Field
|
18 pages, latex2e amsart document class, 4 figures (in separate .eps
files)
| null | null | null |
quant-ph
| null |
In the paper, analysis of a quantum optical system--three-level atom in a
quantum electromagnetic field is given. Evolution operators are constructed in
closed form.
|
[
{
"version": "v1",
"created": "Sat, 1 Apr 2006 17:04:53 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Giorgadze",
"G.",
""
],
[
"Melikishvili",
"Z.",
""
]
] |
quant-ph/0604004
|
Gia Giorgadze
|
G. Giorgadze and R. Tevzadze
|
Quantum computation with scattering matrices
|
15 pages, latex2e amsart document class
| null | null | null |
quant-ph
| null |
We discuss possible applications of the 1-D direct and inverse scattering
problem to design of universal quantum gates for quantum computation. The
potentials generating some universal gates are described.
|
[
{
"version": "v1",
"created": "Sat, 1 Apr 2006 17:14:58 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Giorgadze",
"G.",
""
],
[
"Tevzadze",
"R.",
""
]
] |
quant-ph/0604005
|
J. G. Muga
|
F. Delgado, J. G. Muga, G. Garcia-Calderon
|
Suppression of Zeno effect for distant detectors
|
4 pages, 4 figures
| null |
10.1103/PhysRevA.74.062102
| null |
quant-ph
| null |
We describe the influence of continuous measurement in a decaying system and
the role of the distance from the detector to the initial location of the
system. The detector is modeled first by a step absorbing potential. For a
close and strong detector, the decay rate of the system is reduced; weaker
detectors do not modify the exponential decay rate but suppress the long-time
deviations above a coupling threshold. Nevertheless, these perturbing effects
of measurement disappear by increasing the distance between the initial state
and the detector, as well as by improving the efficiency of the detector.
|
[
{
"version": "v1",
"created": "Sun, 2 Apr 2006 07:09:58 GMT"
},
{
"version": "v2",
"created": "Thu, 27 Jul 2006 09:59:43 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Delgado",
"F.",
""
],
[
"Muga",
"J. G.",
""
],
[
"Garcia-Calderon",
"G.",
""
]
] |
quant-ph/0604006
|
Rebecca Hihinashvili
|
Rebecca Hihinashvili, Tali Oliker, Yaniv S. Avizrats, Alexander Iomin,
Shmuel Fishman, Italo Guarneri
|
Regimes of stability of accelerator modes
|
Submitted to Physica D
| null |
10.1016/j.physd.2006.10.008
| null |
quant-ph
| null |
The phase diagram of a simple area-preserving map, which was motivated by the
quantum dynamics of cold atoms, is explored analytically and numerically.
Periodic orbits of a given winding ratio are found to exist within wedge-shaped
regions in the phase diagrams, which are analogous to the Arnol'd tongues which
have been extensively studied for a variety of dynamical systems, mostly
dissipative ones. A rich variety of bifurcations of various types are observed,
as well as period doubling cascades. Stability of periodic orbits is analyzed
in detail.
|
[
{
"version": "v1",
"created": "Sun, 2 Apr 2006 13:19:58 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Hihinashvili",
"Rebecca",
""
],
[
"Oliker",
"Tali",
""
],
[
"Avizrats",
"Yaniv S.",
""
],
[
"Iomin",
"Alexander",
""
],
[
"Fishman",
"Shmuel",
""
],
[
"Guarneri",
"Italo",
""
]
] |
quant-ph/0604007
|
Doyeol (David) Ahn
|
D. Ahn and M. S. Kim
|
Hawking-Unruh effect and the entanglement of two-mode squeezed states in
Riemannian spacetime
|
Phys. Lett. A, accepted for publication
|
Phys.Lett.A366:202-205,2007
|
10.1016/j.physleta.2007.01.072
| null |
quant-ph hep-th
| null |
We consider the system of free scalar field, which is assumed to be a
two-mode squeezed state from an inertial point of view. This setting allows the
use of entanglement measure for continuous variables, which can be applied to
discuss free and bound entanglement from the point of view from non-inertial
observer.
|
[
{
"version": "v1",
"created": "Sun, 2 Apr 2006 14:14:25 GMT"
},
{
"version": "v2",
"created": "Tue, 4 Apr 2006 06:18:38 GMT"
},
{
"version": "v3",
"created": "Wed, 31 Jan 2007 02:39:05 GMT"
}
] | 2008-11-26T00:00:00 |
[
[
"Ahn",
"D.",
""
],
[
"Kim",
"M. S.",
""
]
] |
quant-ph/0604008
|
Gerard Hooft 't
|
Gerard 't Hooft
|
The mathematical basis for deterministic quantum mechanics
|
17 pages, 3 figures. Minor corrections, comments and explanations
added
| null |
10.1088/1742-6596/67/1/012015
|
ITP-UU-06/14, SPIN-06/12
|
quant-ph gr-qc
| null |
If there exists a classical, i.e. deterministic theory underlying quantum
mechanics, an explanation must be found of the fact that the Hamiltonian, which
is defined to be the operator that generates evolution in time, is bounded from
below. The mechanism that can produce exactly such a constraint is identified
in this paper. It is the fact that not all classical data are registered in the
quantum description. Large sets of values of these data are assumed to be
indistinguishable, forming equivalence classes. It is argued that this should
be attributed to information loss, such as what one might suspect to happen
during the formation and annihilation of virtual black holes.
The nature of the equivalence classes is further elucidated, as it follows
from the positivity of the Hamiltonian. Our world is assumed to consist of a
very large number of subsystems that may be regarded as approximately
independent, or weakly interacting with one another. As long as two (or more)
sectors of our world are treated as being independent, they all must be
demanded to be restricted to positive energy states only. What follows from
these considerations is a unique definition of energy in the quantum system in
terms of the periodicity of the limit cycles of the deterministic model.
|
[
{
"version": "v1",
"created": "Mon, 3 Apr 2006 18:17:08 GMT"
},
{
"version": "v2",
"created": "Mon, 26 Jun 2006 11:32:51 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Hooft",
"Gerard 't",
""
]
] |
quant-ph/0604009
|
Koji Azuma
|
Koji Azuma, Masato Koashi, Hosho Katsura, Nobuyuki Imoto
|
Quantum cloning with nonlocal assistance: Complement of Jozsa's stronger
no-cloning theorem
|
4 pages, 1 figure
| null | null | null |
quant-ph
| null |
We investigate the cases where a set $S$ of states $\{\ket{\psi_i} \}$ cannot
be cloned by itself, but is clonable with the help of another system prepared
in state $\hat{\rho}_i$. When $S$ is pair-wise nonorthogonal, it is known that
one can generate the copy from $\hat{\rho}_i$ alone, with no interaction with
the original system. Here we show that a set containing orthogonal pairs
exhibits a property forming a striking contrast; For any such set, there is a
choice of $\hat{\rho}_i$ that enables cloning only when the two systems are
interacted in a purely quantum manner that is not achievable via classical
communication.
|
[
{
"version": "v1",
"created": "Mon, 3 Apr 2006 08:09:18 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Azuma",
"Koji",
""
],
[
"Koashi",
"Masato",
""
],
[
"Katsura",
"Hosho",
""
],
[
"Imoto",
"Nobuyuki",
""
]
] |
quant-ph/0604010
|
Maarten Van den Nest
|
Maarten Van den Nest, Akimasa Miyake, Wolfgang D\"ur, and Hans J.
Briegel
|
Universal resources for measurement-based quantum computation
|
4 pages, 1 figure; final version
|
Phys. Rev. Lett. 97, 150504 (2006)
|
10.1103/PhysRevLett.97.150504
| null |
quant-ph
| null |
We investigate which entanglement resources allow universal measurement-based
quantum computation via single-qubit operations. We find that any entanglement
feature exhibited by the 2D cluster state must also be present in any other
universal resource. We obtain a powerful criterion to assess universality of
graph states, by introducing an entanglement measure which necessarily grows
unboundedly with the system size for all universal resource states.
Furthermore, we prove that graph states associated with 2D lattices such as the
hexagonal and triangular lattice are universal, and obtain the first example of
a universal non-graph state.
|
[
{
"version": "v1",
"created": "Mon, 3 Apr 2006 19:45:15 GMT"
},
{
"version": "v2",
"created": "Mon, 16 Oct 2006 15:55:09 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Nest",
"Maarten Van den",
""
],
[
"Miyake",
"Akimasa",
""
],
[
"Dür",
"Wolfgang",
""
],
[
"Briegel",
"Hans J.",
""
]
] |
quant-ph/0604011
|
Francesco Plastina
|
Francesco Plastina, Giuseppe Liberti, Angelo Carollo
|
Scaling of Berry's Phase Close to the Dicke Quantum Phase Transition
| null |
Europhys.Lett. 76, 182 (2006)
|
10.1209/epl/i2006-10270-x
| null |
quant-ph
| null |
We discuss the thermodynamic and finite size scaling properties of the
geometric phase in the adiabatic Dicke model, describing the super-radiant
phase transition for an $N$ qubit register coupled to a slow oscillator mode.
We show that, in the thermodynamic limit, a non zero Berry phase is obtained
only if a path in parameter space is followed that encircles the critical
point. Furthermore, we investigate the precursors of this critical behavior for
a system with finite size and obtain the leading order in the 1/N expansion of
the Berry phase and its critical exponent.
|
[
{
"version": "v1",
"created": "Tue, 4 Apr 2006 03:50:52 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Plastina",
"Francesco",
""
],
[
"Liberti",
"Giuseppe",
""
],
[
"Carollo",
"Angelo",
""
]
] |
quant-ph/0604012
|
Mattias Marklund
|
L. Stenflo, P. K. Shukla, and M. Marklund
|
New low frequency oscillations in quantum dusty plasmas
|
5 pages, to appear in Europhys. Lett
|
Europhys. Lett. 74, 844 (2006)
|
10.1209/epl/i2006-10032-x
| null |
quant-ph
| null |
The existence of two new low-frequency electrostatic modes in quantum dusty
plasmas is pointed out. These modes can be useful to diagnose charged dust
impurities in micro-electro-mechanical systems.
|
[
{
"version": "v1",
"created": "Tue, 4 Apr 2006 06:10:50 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Stenflo",
"L.",
""
],
[
"Shukla",
"P. K.",
""
],
[
"Marklund",
"M.",
""
]
] |
quant-ph/0604013
|
Garry Bowen
|
Garry Bowen and Nilanjana Datta
|
Beyond i.i.d. in Quantum Information Theory
|
6 Pages, requires IEEEtran.cls, updated and corrected proofs
| null | null | null |
quant-ph cs.IT math.IT
| null |
The information spectrum approach gives general formulae for optimal rates of
codes in many areas of information theory. In this paper the quantum spectral
divergence rates are defined and properties of the rates are derived. The
entropic rates, conditional entropic rates, and spectral mutual information
rates are then defined in terms of the spectral divergence rates. Properties
including subadditivity, chain rules, Araki-Lieb inequalities, and monotonicity
are then explored.
|
[
{
"version": "v1",
"created": "Tue, 4 Apr 2006 11:11:47 GMT"
},
{
"version": "v2",
"created": "Mon, 16 Oct 2006 11:07:08 GMT"
}
] | 2007-07-13T00:00:00 |
[
[
"Bowen",
"Garry",
""
],
[
"Datta",
"Nilanjana",
""
]
] |
quant-ph/0604014
|
Andreas Fring
|
Carla Figueira de Morisson Faria and Andreas Fring
|
Time evolution of non-Hermitian Hamiltonian systems
|
25 pages Latex, 1 eps figure, references added
|
J. Phys. A 39 (2006) 9269-9289
|
10.1088/0305-4470/39/29/018
|
CMS 01/06
|
quant-ph math-ph math.MP
| null |
We provide time-evolution operators, gauge transformations and a perturbative
treatment for non-Hermitian Hamiltonian systems, which are explicitly
time-dependent. We determine various new equivalence pairs for Hermitian and
non-Hermitian Hamiltonians, which are therefore pseudo-Hermitian and in
addition in some cases also invariant under PT-symmetry. In particular, for the
harmonic oscillator perturbed by a cubic non-Hermitian term, we evaluate
explicitly various transition amplitudes, for the situation when these systems
are exposed to a monochromatic linearly polarized electric field.
|
[
{
"version": "v1",
"created": "Tue, 4 Apr 2006 18:56:03 GMT"
},
{
"version": "v2",
"created": "Wed, 12 Apr 2006 16:49:31 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Faria",
"Carla Figueira de Morisson",
""
],
[
"Fring",
"Andreas",
""
]
] |
quant-ph/0604015
|
Pramod Joag
|
Ali Ahanj and Pramod Joag
|
Minimum communication cost of simulating quantum correlations is one
cbit for all spin singlet states
|
The paper has been withdrawn
| null | null | null |
quant-ph
| null |
This paper has been withdrawn due to a fatal error in the argument of the
simulation scheme.
|
[
{
"version": "v1",
"created": "Tue, 4 Apr 2006 15:38:21 GMT"
},
{
"version": "v2",
"created": "Wed, 5 Apr 2006 12:04:42 GMT"
},
{
"version": "v3",
"created": "Tue, 25 Apr 2006 11:56:59 GMT"
},
{
"version": "v4",
"created": "Fri, 15 Jun 2007 08:55:11 GMT"
}
] | 2011-11-09T00:00:00 |
[
[
"Ahanj",
"Ali",
""
],
[
"Joag",
"Pramod",
""
]
] |
quant-ph/0604016
|
Marcel Novaes
|
J.P. Keating, F. Mezzadri and M. Novaes
|
Comb entanglement in quantum spin chains
|
6 pages, 4 figures
|
Phys. Rev. A 74, 012311 (2006)
|
10.1103/PhysRevA.74.012311
| null |
quant-ph
| null |
Bipartite entanglement in the ground state of a chain of $N$ quantum spins
can be quantified either by computing pairwise concurrence or by dividing the
chain into two complementary subsystems. In the latter case the smaller
subsystem is usually a single spin or a block of adjacent spins and the
entanglement differentiates between critical and non-critical regimes. Here we
extend this approach by considering a more general setting: our smaller
subsystem $S_A$ consists of a {\it comb} of $L$ spins, spaced $p$ sites apart.
Our results are thus not restricted to a simple `area law', but contain
non-local information, parameterized by the spacing $p$. For the XX model we
calculate the von-Neumann entropy analytically when $N\to \infty$ and
investigate its dependence on $L$ and $p$. We find that an external magnetic
field induces an unexpected length scale for entanglement in this case.
|
[
{
"version": "v1",
"created": "Tue, 4 Apr 2006 15:54:48 GMT"
}
] | 2007-12-04T00:00:00 |
[
[
"Keating",
"J. P.",
""
],
[
"Mezzadri",
"F.",
""
],
[
"Novaes",
"M.",
""
]
] |
quant-ph/0604017
|
Jan Perina Jr.
|
Jan Perina Jr., Marco Centini, Concita Sibilia, Mario Bertolotti,
Michael Scalora
|
Properties of entangled photon pairs generated in one-dimensional
nonlinear photonic-band-gap structures
|
14 pages, 23 figures
|
Physical Review A 73, 033823 (2006)
|
10.1103/PhysRevA.73.033823
| null |
quant-ph
| null |
We have developed a rigorous quantum model of spontaneous parametric
down-conversion in a nonlinear 1D photonic-band-gap structure based upon
expansion of the field into monochromatic plane waves. The model provides a
two-photon amplitude of a created photon pair. The spectra of the signal and
idler fields, their intensity profiles in the time domain, as well as the
coincidence-count interference pattern in a Hong-Ou-Mandel interferometer are
determined both for cw and pulsed pumping regimes in terms of the two-photon
amplitude. A broad range of parameters characterizing the emitted
down-converted fields can be used. As an example, a structure composed of 49
layers of GaN/AlN is analyzed as a suitable source of photon pairs having high
efficiency.
|
[
{
"version": "v1",
"created": "Tue, 4 Apr 2006 18:10:08 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Perina",
"Jan",
"Jr."
],
[
"Centini",
"Marco",
""
],
[
"Sibilia",
"Concita",
""
],
[
"Bertolotti",
"Mario",
""
],
[
"Scalora",
"Michael",
""
]
] |
quant-ph/0604018
|
Philippe Jacquod
|
Cyril Petitjean and Philippe Jacquod
|
Quantum Reversibility and Echoes in Interacting Systems
|
4 pages, one figure in .eps format
|
Phys. Rev. Lett. 97, 124103 (2006)
|
10.1103/PhysRevLett.97.124103
| null |
quant-ph cond-mat.mes-hall physics.optics
| null |
In Echo experiments, imperfect time-reversal operations are performed on a
subset of the total number of degrees of freedom. To capture the physics of
these experiments, we introduce a partial fidelity, the Boltzmann echo, where
only part of the system's degrees of freedom can be time-reversed. We present a
semiclassical calculation of the Boltzmann echo. We show that, as the
time-reversal operation is performed more and more accurately, the decay rate
of the Boltzmann echo saturates at a value given by the decoherence rate of the
controlled degrees of freedom due to their coupling to uncontrolled ones. We
connect these results with NMR spin echo experiments.
|
[
{
"version": "v1",
"created": "Tue, 4 Apr 2006 23:24:00 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Petitjean",
"Cyril",
""
],
[
"Jacquod",
"Philippe",
""
]
] |
quant-ph/0604019
|
Farhan Saif
|
Farhan Saif
|
Recurrence Tracking Microscope
| null |
Physical Review A 73, 033618 (2006)
|
10.1103/PhysRevA.73.033618
| null |
quant-ph physics.optics
| null |
In order to probe nanostructures on a surface we present a microscope based
on the quantum recurrence phenomena. A cloud of atoms bounces off an atomic
mirror connected to a cantilever and exhibits quantum recurrences. The times at
which the recurrences occur depend on the initial height of the bouncing atoms
above the atomic mirror, and vary following the structures on the surface under
investigation. The microscope has inherent advantages over existing techniques
of scanning tunneling microscope and atomic force microscope. Presently
available experimental technology makes it possible to develop the device in
the laboratory.
|
[
{
"version": "v1",
"created": "Tue, 4 Apr 2006 23:27:29 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Saif",
"Farhan",
""
]
] |
quant-ph/0604020
|
Jun-Hong An
|
Jun-Hong An, Shun-Jin Wang, and Hong-Gang Luo
|
Entanglement dynamics of qubits in a common environment
|
The final version
|
Physica A 382 (2007) 753-764
|
10.1016/j.physa.2007.04.008
| null |
quant-ph
| null |
We use the quantum jump approach to study the entanglement dynamics of a
quantum register, which is composed of two or three dipole-dipole coupled
two-level atoms, interacting with a common environment. Our investigation of
entanglement dynamics reflects that the environment has dual actions on the
entanglement of the qubits in the model. While the environment destroys the
entanglement induced by the coherent dipole-dipole interactions, it can produce
stable entanglement between the qubits prepared initially in a separable state.
The analysis shows that it is the entangled decoherence-free states contained
as components in the initial state that contribute to the stable entanglement.
Our study indicates how the environmental noise produces the entanglement and
exposes the interplay of environmental noise and coherent interactions of
qubits on the entanglement.
|
[
{
"version": "v1",
"created": "Wed, 5 Apr 2006 07:02:42 GMT"
},
{
"version": "v2",
"created": "Sun, 24 Jun 2007 02:50:38 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"An",
"Jun-Hong",
""
],
[
"Wang",
"Shun-Jin",
""
],
[
"Luo",
"Hong-Gang",
""
]
] |
quant-ph/0604021
|
Koray Koksal
|
B. Gonul and K. Koksal
|
A search on the Nikiforov-Uvarov formalism
|
10 pages
|
Phys. Scr. 75 (2007) 686--690
|
10.1088/0031-8949/75/5/017
| null |
quant-ph
| null |
An alternative treatment is proposed for the calculations carried out within
the frame of Nikiforov-Uvarov method, which removes a drawback in the original
theory and by pass some difficulties in solving the Schrodinger equation. The
present procedure is illustrated with the example of orthogonal polynomials.
The relativistic extension of the formalism is discussed.
|
[
{
"version": "v1",
"created": "Wed, 5 Apr 2006 17:44:17 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Gonul",
"B.",
""
],
[
"Koksal",
"K.",
""
]
] |
quant-ph/0604022
|
Jacques Vigue
|
Alain Miffre (LCAR, PIIM), Marion Jacquey (LCAR), Matthias B\"uchner
(LCAR), G\'erard Tr\'enec (LCAR), Jacques Vigu\'e (LCAR)
|
Vibration induced phase noise in Mach-Zehnder atom interferometers
| null | null |
10.1007/s00340-006-2377-9
| null |
quant-ph
| null |
The high inertial sensitivity of atom interferometers has been used to build
accelerometers and gyrometers but this sensitivity makes these interferometers
very sensitive to the laboratory seismic noise. This seismic noise induces a
phase noise which is large enough to reduce the fringe visibility in many
cases. We develop here a model calculation of this phase noise in the case of
Mach-Zehnder atom interferometers and we apply this model to our thermal
lithium interferometer. We are thus able to explain the observed dependence of
the fringe visibility with the diffraction order. The dynamical model developed
in the present paper should be very useful to further reduce this phase noise
in atom interferometers and this reduction should open the way to improved
interferometers.
|
[
{
"version": "v1",
"created": "Wed, 5 Apr 2006 13:26:39 GMT"
}
] | 2016-08-16T00:00:00 |
[
[
"Miffre",
"Alain",
"",
"LCAR, PIIM"
],
[
"Jacquey",
"Marion",
"",
"LCAR"
],
[
"Büchner",
"Matthias",
"",
"LCAR"
],
[
"Trénec",
"Gérard",
"",
"LCAR"
],
[
"Vigué",
"Jacques",
"",
"LCAR"
]
] |
quant-ph/0604023
|
Arkadiusz Jadczyk
|
Arkadiusz Jadczyk
|
Quantum Fractals. Geometric modeling of quantum jumps with conformal
maps
|
Latex, 20 pages, 3 figures. Paper submitted to the Proceedings of
ICCA7 - the 7th International Conference on Clifford Algebras, Toulouse 2005
| null | null | null |
quant-ph
| null |
Positive matrices in SL(2,C) have a double physical interpretation; they can
be either considered as "fuzzy projections" of a spin 1/2 quantum system, or as
Lorentz boosts. In the present paper, concentrating on this second
interpretation, we follow the clues given by Pertti Lounesto and, using the
classical Clifford algebraic methods, interpret them as conformal maps of the
"heavenly sphere" S^2. The fuzziness parameter of the first interpretation
becomes the "boost velocity" in the second one. We discuss simple iterative
function systems of such maps, and show that they lead to self--similar fractal
patterns on S^2. The final section of this paper is devoted to an informal
discussion of the relations between these concepts and the problems in the
foundations of quantum theory, where the interplay between different kinds of
algebras and maps may enable us to describe not only the continuous evolution
of wave functions, but also quantum jumps and "events" that accompany these
jumps. Paper dedicated to the memory of Pertti Lounesto.
|
[
{
"version": "v1",
"created": "Wed, 5 Apr 2006 13:53:59 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Jadczyk",
"Arkadiusz",
""
]
] |
quant-ph/0604024
|
Gennady Berman
|
Gennady P. Berman, Fausto Borgonovi, and Diego A.R. Dalvit
|
Quantum Dynamical Effects as a Singular Perturbation for Observables in
Open Quasi-Classical Nonlinear Mesoscopic Systems
|
changed contents
| null | null |
LAUR-06-2355
|
quant-ph
| null |
We review our results on a mathematical dynamical theory for observables for
open many-body quantum nonlinear bosonic systems for a very general class of
Hamiltonians. We show that non-quadratic (nonlinear) terms in a Hamiltonian
provide a singular "quantum" perturbation for observables in some "mesoscopic"
region of parameters. In particular, quantum effects result in secular terms in
the dynamical evolution, that grow in time. We argue that even for open quantum
nonlinear systems in the deep quasi-classical region, these quantum effects can
survive after decoherence and relaxation processes take place. We demonstrate
that these quantum effects in open quantum systems can be observed, for
example, in the frequency Fourier spectrum of the dynamical observables, or in
the corresponding spectral density of noise. Estimates are presented for
Bose-Einstein condensates, low temperature mechanical resonators, and nonlinear
optical systems prepared in large amplitude coherent states. In particular, we
show that for Bose-Einstein condensate systems the characteristic time of
deviation of quantum dynamics for observables from the corresponding classical
dynamics coincides with the characteristic time-scale of the well-known quantum
nonlinear effect of phase diffusion.
|
[
{
"version": "v1",
"created": "Wed, 5 Apr 2006 16:45:14 GMT"
},
{
"version": "v2",
"created": "Thu, 4 May 2006 14:00:55 GMT"
},
{
"version": "v3",
"created": "Tue, 29 Jan 2008 09:07:05 GMT"
}
] | 2008-01-29T00:00:00 |
[
[
"Berman",
"Gennady P.",
""
],
[
"Borgonovi",
"Fausto",
""
],
[
"Dalvit",
"Diego A. R.",
""
]
] |
quant-ph/0604025
|
Aeysha Khalique
|
Aeysha Khalique, Georgios M. Nikolopoulos, and Gernot Alber
|
Postponement of dark-count effects in practical quantum key-distribution
by two-way post-processing
|
Fully revised version (12 pages and 8 figures). Improved figures and
discussion added. To appear in Eur. Phys. J. D
|
Eur. Phys. J. D vol. 40, 453-464 (2006)
|
10.1140/epjd/e2006-00167-2
| null |
quant-ph
| null |
The influence of imperfections on achievable secret-key generation rates of
quantum key distribution protocols is investigated. As examples of relevant
imperfections, we consider tagging of Alice's qubits and dark counts at Bob's
detectors, while we focus on a powerful eavesdropping strategy which takes full
advantage of tagged signals. It is demonstrated that error correction and
privacy amplification based on a combination of a two-way classical
communication protocol and asymmetric Calderbank-Shor-Steane codes may
significantly postpone the disastrous influence of dark counts. As a result,
the distances are increased considerably over which a secret key can be
distributed in optical fibres reliably. Results are presented for the
four-state, the six-state, and the decoy-state protocols.
|
[
{
"version": "v1",
"created": "Wed, 5 Apr 2006 16:52:31 GMT"
},
{
"version": "v2",
"created": "Tue, 27 Jun 2006 11:05:17 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Khalique",
"Aeysha",
""
],
[
"Nikolopoulos",
"Georgios M.",
""
],
[
"Alber",
"Gernot",
""
]
] |
quant-ph/0604026
|
Sarah Croke
|
Sarah Croke, Erika Andersson, Stephen M. Barnett, Claire R. Gilson and
John Jeffers
|
Maximum Confidence Quantum Measurements
|
4 pages, 2 figures
|
Phys Rev Lett 96, 070401 (2006)
|
10.1103/PhysRevLett.96.070401
| null |
quant-ph
| null |
We consider the problem of discriminating between states of a specified set
with maximum confidence. For a set of linearly independent states unambiguous
discrimination is possible if we allow for the possibility of an inconclusive
result. For linearly dependent sets an analogous measurement is one which
allows us to be as confident as possible that when a given state is identified
on the basis of the measurement result, it is indeed the correct state.
|
[
{
"version": "v1",
"created": "Wed, 5 Apr 2006 17:00:43 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Croke",
"Sarah",
""
],
[
"Andersson",
"Erika",
""
],
[
"Barnett",
"Stephen M.",
""
],
[
"Gilson",
"Claire R.",
""
],
[
"Jeffers",
"John",
""
]
] |
quant-ph/0604027
|
Stefano Pirandola
|
Stefano Pirandola and Stefano Mancini
|
Quantum Teleportation with Continuous Variables: a survey
|
Review article. 26 pages, 4 figures
|
Laser Physics 16, 1418 (2006)
|
10.1134/S1054660X06100057
| null |
quant-ph physics.optics
| null |
Very recently we have witnessed a new development of quantum information, the
so-called continuous variable (CV) quantum information theory. Such a further
development has been mainly due to the experimental and theoretical advantages
offered by CV systems, i.e., quantum systems described by a set of observables,
like position and momentum, which have a continuous spectrum of eigenvalues.
According to this novel trend, quantum information protocols like quantum
teleportation have been suitably extended to the CV framework. Here, we briefly
review some mathematical tools relative to CV systems and we consequently
develop the concepts of quantum entanglement and teleportation in the CV
framework, by analogy with the qubit-based approach. Some connections between
teleportation fidelity and entanglement properties of the underlying quantum
channel are inspected. Next, we face the study of CV quantum teleportation
networks where more users share a multipartite state and an arbitrary pair of
them performs quantum teleportation. In this context, we show alternative
protocols and we investigate the optimal strategy that maximizes the
performance of the network.
|
[
{
"version": "v1",
"created": "Wed, 5 Apr 2006 17:14:03 GMT"
},
{
"version": "v2",
"created": "Thu, 12 Oct 2006 09:03:42 GMT"
}
] | 2008-06-27T00:00:00 |
[
[
"Pirandola",
"Stefano",
""
],
[
"Mancini",
"Stefano",
""
]
] |
quant-ph/0604028
|
Jacques Vigue
|
A. Miffre (LCAR, Piim), M. Jacquey (LCAR), M. B\"uchner (LCAR), G.
Tr\'enec (LCAR), J. Vigu\'e (LCAR)
|
Phase noise due to vibrations in Mach-Zehnder atom interferometers
| null | null | null | null |
quant-ph
| null |
Atom interferometers are very sensitive to accelerations and rotations. This
property, which has some very interesting applications, induces a deleterious
phase noise due to the seismic noise of the laboratory and this phase noise is
sufficiently large to reduce the fringe visibility in many experiments. We
develop a model calculation of this phase noise in the case of Mach-Zehnder
atom interferometers and we apply this model to our thermal lithium
interferometer. We are able to explain the observed phase noise which has been
detected through the rapid dependence of the fringe visibility with the
diffraction order. We think that the dynamical model developed in the present
paper should be very useful to reduce the vibration induced phase noise in atom
interferometers, making many new experiments feasible.
|
[
{
"version": "v1",
"created": "Wed, 5 Apr 2006 18:59:26 GMT"
}
] | 2016-08-16T00:00:00 |
[
[
"Miffre",
"A.",
"",
"LCAR, Piim"
],
[
"Jacquey",
"M.",
"",
"LCAR"
],
[
"Büchner",
"M.",
"",
"LCAR"
],
[
"Trénec",
"G.",
"",
"LCAR"
],
[
"Vigué",
"J.",
"",
"LCAR"
]
] |
quant-ph/0604029
|
Diogenes Galetti
|
D. Galetti
|
A new description of spin tunneling in magnetic molecules
|
7 pages, 2 figures
| null |
10.1016/j.physa.2006.07.030
| null |
quant-ph cond-mat.mes-hall
| null |
A new approach is used that allows to describe the magnetic molecules main
properties in a direct and simple way. Results obtained for the Fe8 cluster
show good agreement with the experimental data.
|
[
{
"version": "v1",
"created": "Wed, 5 Apr 2006 19:01:20 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Galetti",
"D.",
""
]
] |
quant-ph/0604030
|
Matthias Jakob
|
Ian Glendinning, Matthias Jakob and Michael Noelle
|
Non-Markovian thermalization of entangled qubits
|
10 pages, 11 Postscript figures
| null | null | null |
quant-ph
| null |
We study the decoherence properties of an entangled bipartite qubit system,
represented by two two-level atoms that are individually coupled to
non-Markovian reservoirs. This coupling ensures that the dynamical equations of
the atoms can be treated independently. The non-Markovian reservoirs are
described by a model which leads to an exact non-Markovian master equation of
the Nakajima-Zwanzig form [J. Salo, S. M. Barnett, and S. Stenholm, Optics
Commun. 259, 772 (2006)]. We consider the evolution of the entanglement of a
two-atom state that is initially completely entangled, quantified by its
concurrence. Collapses and revivals in the concurrence, induced by the memory
effects of the reservoir, govern the dynamics of the entangled quantum system.
These collapses and revivals in the concurrence are a strong manifestation of
the non-Markovian reservoir.
|
[
{
"version": "v1",
"created": "Wed, 5 Apr 2006 19:18:25 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Glendinning",
"Ian",
""
],
[
"Jakob",
"Matthias",
""
],
[
"Noelle",
"Michael",
""
]
] |
quant-ph/0604031
|
Vahid Karimipour
|
M. Asoudeh and V. Karimipour
|
Thermal entanglement of spins in mean-field clusters
|
16 pages, 11 figures
|
Physical Review A 73, 062109 (2006)
|
10.1103/PhysRevA.73.062109
| null |
quant-ph
| null |
We determine thermal entanglement in mean field clusters of $N$ spin one-half
particles interacting via the anisotropic Heisenberg interaction, with and
without external magnetic field. For the $xxx$ cluster in the absence of
magnetic field we prove that only the N=2 ferromagnetic cluster shows
entanglement. An external magnetic field $B$ can only entangle $xxx$
anti-ferromagnetic clusters in certain regions of the $B-T$ plane. On the other
hand, the $xxz$ clusters of size $N>2$ are entangled only when the interaction
is ferromagnetic. Detailed dependence of the entanglement on various parameters
is investigated in each case.
|
[
{
"version": "v1",
"created": "Wed, 5 Apr 2006 19:22:40 GMT"
},
{
"version": "v2",
"created": "Sat, 8 Apr 2006 00:16:40 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Asoudeh",
"M.",
""
],
[
"Karimipour",
"V.",
""
]
] |
quant-ph/0604032
|
Carlos Farina
|
T.N.C.Mendes and C. Farina
|
Excited state contribution to the Casimir-Polder force at finite
temperature
|
3 pages, 3 figures
| null | null | null |
quant-ph
| null |
Using the master equation we calculate the contribution of the excited state
of a two-level atom to its interacting potential with a perfectly conducting
wall at finite temperature. For low temperature, $\hbar \omega_0/k_B T = k_0
\lambda_T\gg 1$, where $\omega_0 = k_0 c$ is the transition frequency of the
atom and $\lambda_T$ is the thermal wavelength, we show that this contribution
is very small $(\propto e^{-k_0\lambda_T})$. In the opposite limit
$(k_0\lambda_T \ll 1)$, however, we show that the expression for the
interacting potential, for all relevant distance regimes, becomes exactly the
same as that for very short distances $(k_0 z \ll 1)$ and with the field in the
vacuum state.
|
[
{
"version": "v1",
"created": "Wed, 5 Apr 2006 20:22:08 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Mendes",
"T. N. C.",
""
],
[
"Farina",
"C.",
""
]
] |
quant-ph/0604033
|
Carlos Farina
|
T.N.C. Mendes and C. Farina
|
Casimir-Polder forces from density matrix formalism
|
11 pages, 3 figures
| null |
10.1088/0305-4470/39/21/S51
| null |
quant-ph
| null |
We use the density matrix formalism in order to calculate the energy level
shifts, in second order on interaction, of an atom in the presence of a
perfectly conducting wall in the dipole approximation. The thermal corrections
are also examined when $\hbar \omega_0/k_B T = k_0 \lambda_T \gg 1$, where
${$\omega_0=k_0 c$}$ is the dominant transition frequency of the atom and
$\lambda_T$ is the thermal length. When the distance $z$ between the atom and
the wall is larger than $\lambda_T$ we find the well known result obtained from
Lifshitz's formula, whose leading term is proportional to temperature and is
independent of $c$, $\hbar$ and $k_0$. In the short distance limit, when
$z\ll\lambda_T$, only very small corrections to the leading vacuum term occur.
We also show, for all distance regimes, that the main thermal corrections are
independent of $k_0$ (dispersion is not important) and dependent of $c$, which
means that there is not a non-retarded regime for the thermal contributions.
|
[
{
"version": "v1",
"created": "Wed, 5 Apr 2006 20:54:11 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Mendes",
"T. N. C.",
""
],
[
"Farina",
"C.",
""
]
] |
quant-ph/0604034
|
Carlos Farina
|
T.N.C. Mendes and C. Farina
|
A master equation approach for the interaction of an atom with a
dielectric semi-infinite medium
|
9 pages
| null | null | null |
quant-ph
| null |
We use the master equation approach to calculate the energy level shifts of
an atom in the presence of a general dielectric semi-infinite medium
characterized by a dielectric constant $\epsilon(\omega)$. Particularly, we
analyze the case of a non-dispersive medium for which we obtain a general
expression for the interaction as well as the asymptotic behaviors for $k_0 z
\ll 1$ (non-retarded regime) and $k_0 z \gg 1$ (retarded regime), where
$\omega_0 = k_0 c$ is the main transition frequency of the atom. The limiting
cases $\epsilon \simeq 1$ and $\epsilon \gg 1$ are discussed for both retarded
and non-retarded limits. For the retarded limit, we compute the non-additivity
contribution of van der Waals forces.
|
[
{
"version": "v1",
"created": "Wed, 5 Apr 2006 21:06:01 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Mendes",
"T. N. C.",
""
],
[
"Farina",
"C.",
""
]
] |
quant-ph/0604035
|
Zhang Zhanjun Dr.
|
Zhan-jun Zhang
|
The security proof of the ping-pong protocol is wrong
|
Any suggestion or comment is welcome!!
| null | null | null |
quant-ph
| null |
The security proof of the ping-pong protocol is wrong.
|
[
{
"version": "v1",
"created": "Thu, 6 Apr 2006 00:48:04 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Zhang",
"Zhan-jun",
""
]
] |
quant-ph/0604036
|
Osamu Hirota
|
Osamu Hirota, and Kaoru Kurosawa
|
An immunity against correlation attack on quantum stream cipher by Yuen
2000 protocol
|
5 pages
| null | null | null |
quant-ph
| null |
This paper presents the security analysis on the quantum stream cipher so
called Yuen-2000 protocol (or $\alpha\eta$ scheme) against the fast correlation
attack, the typical attack on stream ciphers. Although a very simple
experimental model of the quantum stream cipher without a random mapper may be
decrypted in the information theoretic sense by the fast correlation algorithm,
it is not a basic feature of Yuen 2000 protocol. In fact, we clarify that there
exists a randomization scheme which attains the perfect correlation immunity
against such attacks under an approximation. And in this scheme, the running
key correlation from the second randomization that determines the mapping
patterns is dismissed also by quantum noise. In such a case, any fast
correlation attack does not work on the quantum stream cipher.
|
[
{
"version": "v1",
"created": "Thu, 6 Apr 2006 04:44:23 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Hirota",
"Osamu",
""
],
[
"Kurosawa",
"Kaoru",
""
]
] |
quant-ph/0604037
|
Alexey Gorshkov
|
Alexey V. Gorshkov, Axel Andre, Michael Fleischhauer, Anders S.
Sorensen, Mikhail D. Lukin
|
Universal Approach to Optimal Photon Storage in Atomic Media
|
4 pages, 3 figures. V2: major changes in presentation (title,
abstract, main text), simplification of derivations, new references. V3:
minor changes - final version as published in Phys. Rev. Lett
|
Phys. Rev. Lett. 98, 123601 (2007)
|
10.1103/PhysRevLett.98.123601
| null |
quant-ph
| null |
We present a universal physical picture for describing storage and retrieval
of photon wave packets in a Lambda-type atomic medium. This physical picture
encompasses a variety of different approaches to pulse storage ranging from
adiabatic reduction of the photon group velocity and pulse-propagation control
via off-resonant Raman fields to photon-echo based techniques. Furthermore, we
derive an optimal control strategy for storage and retrieval of a photon wave
packet of any given shape. All these approaches, when optimized, yield
identical maximum efficiencies, which only depend on the optical depth of the
medium.
|
[
{
"version": "v1",
"created": "Thu, 6 Apr 2006 18:20:33 GMT"
},
{
"version": "v2",
"created": "Mon, 11 Dec 2006 23:03:21 GMT"
},
{
"version": "v3",
"created": "Wed, 28 Mar 2007 04:53:23 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Gorshkov",
"Alexey V.",
""
],
[
"Andre",
"Axel",
""
],
[
"Fleischhauer",
"Michael",
""
],
[
"Sorensen",
"Anders S.",
""
],
[
"Lukin",
"Mikhail D.",
""
]
] |
quant-ph/0604038
|
Lorenzo Maccone
|
Lorenzo Maccone
|
Entropic information-disturbance tradeoff
|
4 pages, 1 figure. Revised version
|
Europhys. Lett. 77, 40002 (2007)
|
10.1209/0295-5075/77/40002
| null |
quant-ph
| null |
We show the flaws found in the customary fidelity-based definitions of
disturbance in quantum measurements and evolutions. We introduce the "entropic
disturbance" D and show that it adequately measures the degree of disturbance,
intended essentially as an irreversible change in the state of the system. We
also find that it complies with an information-disturbance tradeoff, namely the
mutual information between the eigenvalues of the initial state and the
measurement results is less than or equal to D.
|
[
{
"version": "v1",
"created": "Thu, 6 Apr 2006 08:44:01 GMT"
},
{
"version": "v2",
"created": "Mon, 26 Jun 2006 09:12:39 GMT"
},
{
"version": "v3",
"created": "Wed, 6 Sep 2006 07:39:02 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Maccone",
"Lorenzo",
""
]
] |
quant-ph/0604039
|
Franco Ventriglia
|
V.I. Man'ko, G. Marmo, A. Simoni, F. Ventriglia
|
Tomography in abstract Hilbert spaces
|
16 pages, presented at Palermo "TQMFA2005" Conference. To appear on
"Open Systems & Information Dynamics" (2006)
| null | null | null |
quant-ph hep-th math-ph math.MP
| null |
The tomographic description of a quantum state is formulated in an abstract
infinite dimensional Hilbert space framework, the space of the Hilbert-Schmidt
linear operators, with trace formula as scalar product. Resolutions of the
unity, written in terms of over-complete sets of rank-one projectors and of
associated Gram-Schmidt operators taking into account their non-orthogonality,
are then used to reconstruct a quantum state from its tomograms. Examples of
well known tomographic descriptions illustrate the exposed theory.
|
[
{
"version": "v1",
"created": "Thu, 6 Apr 2006 09:05:19 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Man'ko",
"V. I.",
""
],
[
"Marmo",
"G.",
""
],
[
"Simoni",
"A.",
""
],
[
"Ventriglia",
"F.",
""
]
] |
quant-ph/0604040
|
Tom Savels
|
Tom Savels, Allard P. Mosk and Ad Lagendijk
|
Gain narrowing in few-atom systems
| null |
Phys. Rev. Lett. 98, 103601 (2007)
|
10.1103/PhysRevLett.98.103601
| null |
quant-ph
| null |
Using a density matrix approach, we study the simplest systems that display
both gain and feedback: clusters of 2 to 5 atoms, one of which is pumped. The
other atoms supply feedback through multiple scattering of light. We show that,
if the atoms are in each other's near-field, the system exhibits large gain
narrowing and spectral mode redistribution. The observed phenomena are more
pronounced if the feedback is enhanced. Our system is to our knowledge the
simplest exactly solvable microscopic system which shows the approach to laser
oscillation.
|
[
{
"version": "v1",
"created": "Thu, 6 Apr 2006 09:36:48 GMT"
},
{
"version": "v2",
"created": "Wed, 31 May 2006 21:03:08 GMT"
}
] | 2015-06-26T00:00:00 |
[
[
"Savels",
"Tom",
""
],
[
"Mosk",
"Allard P.",
""
],
[
"Lagendijk",
"Ad",
""
]
] |
quant-ph/0604041
|
Ramazan Sever
|
Cevdet Tezcan and Ramazan Sever
|
Exact Solutions of the Schr\"{o}dinger Equation with position-dependent
effective mass via general point canonical transformation
|
12 pages
|
J. Math. Chem. 42, 387(2007)
|
10.1007/s10773-007-9589-6
| null |
quant-ph
| null |
Exact solutions of the Schrodinger equation are obtained for the Rosen-Morse
and Scarf potentials with the position-dependent effective mass by appliying a
general point canonical transformation. The general form of the point canonical
transformation is introduced by using a free parameter. Two different forms of
mass distributions are used. A set of the energy eigenvalues of the bound
states and corresponding wave functions for target potentials are obtained as a
function of the free parameter.
|
[
{
"version": "v1",
"created": "Thu, 6 Apr 2006 11:21:27 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Tezcan",
"Cevdet",
""
],
[
"Sever",
"Ramazan",
""
]
] |
quant-ph/0604042
|
Erik Sjoqvist
|
Erik Sj\"oqvist
|
Geometric phase in weak measurements
|
Some additional material, journal reference added
|
Phys. Lett. A 359, 187 (2006)
|
10.1016/j.physleta.2006.06.028
| null |
quant-ph
| null |
Pancharatnam's geometric phase is associated with the phase of a
complex-valued weak value arising in a certain type of weak measurement in pre-
and post-selected quantum ensembles. This makes it possible to test the
nontransitive nature of the relative phase in quantum mechanics, in the weak
measurement scenario.
|
[
{
"version": "v1",
"created": "Thu, 6 Apr 2006 11:53:59 GMT"
},
{
"version": "v2",
"created": "Wed, 27 Sep 2006 07:50:54 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Sjöqvist",
"Erik",
""
]
] |
quant-ph/0604043
|
Morten Bache
|
M. Bache, D. Magatti, A. Gatti, E. Brambilla, F. Ferri, and L.A.
Lugiato
|
Coherent imaging of a pure phase object with classical incoherent light
|
13 pages, 11 figures. Published in Physical Review A. Replaced
version fixes some problems with Figs. 1, 4 and 10
|
Phys. Rev. A 73, 053802 (2006)
|
10.1103/PhysRevA.73.053802
| null |
quant-ph
| null |
By using the ghost imaging technique, we experimentally demonstrate the
reconstruction of the diffraction pattern of a {\em pure phase} object by using
the classical correlation of incoherent thermal light split on a beam splitter.
The results once again underline that entanglement is not a necessary feature
of ghost imaging. The light we use is spatially highly incoherent with respect
to the object ($\approx 2 \mu$m speckle size) and is produced by a
pseudo-thermal source relying on the principle of near-field scattering. We
show that in these conditions no information on the phase object can be
retrieved by only measuring the light that passed through it, neither in a
direct measurement nor in a Hanbury Brown-Twiss (HBT) scheme. In general, we
show a remarkable complementarity between ghost imaging and the HBT scheme when
dealing with a phase object.
|
[
{
"version": "v1",
"created": "Thu, 6 Apr 2006 13:14:10 GMT"
},
{
"version": "v2",
"created": "Thu, 6 Jul 2006 11:16:33 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Bache",
"M.",
""
],
[
"Magatti",
"D.",
""
],
[
"Gatti",
"A.",
""
],
[
"Brambilla",
"E.",
""
],
[
"Ferri",
"F.",
""
],
[
"Lugiato",
"L. A.",
""
]
] |
quant-ph/0604044
|
Francesco Zaccaria
|
Olga V. Man'ko, V.I. Man'ko, G. Marmo, E.C.G. Sudarshan, F. Zaccaria
|
Does The Uncertainty Relation Determine The Quantum State?
|
11 pages, to be submitted to Physics Letters A
|
Phys.Lett. A357 (2006) 255-260
|
10.1016/j.physleta.2006.04.116
| null |
quant-ph
| null |
The example of nonpositive trace-class Hermitian operator for which
Robertson-Schroedinger uncertainty relation is fulfilled is presented. The
partial scaling criterion of separability of multimode continuous variable
system is discussed in the context of using nonpositive maps of density
matrices.
|
[
{
"version": "v1",
"created": "Thu, 6 Apr 2006 16:07:46 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Man'ko",
"Olga V.",
""
],
[
"Man'ko",
"V. I.",
""
],
[
"Marmo",
"G.",
""
],
[
"Sudarshan",
"E. C. G.",
""
],
[
"Zaccaria",
"F.",
""
]
] |
quant-ph/0604045
|
Yeong-Cherng Liang
|
Yeong-Cherng Liang and Andrew C. Doherty
|
Better Bell Inequality Violation by Collective Measurements
|
7 pages, 4 figures and 1 table; references updated
|
Physical Review A, vol. 73, art. 052116 (2006)
|
10.1103/PhysRevA.73.052116
| null |
quant-ph
| null |
The standard Bell inequality experiments test for violation of local realism
by repeatedly making local measurements on individual copies of an entangled
quantum state. Here we investigate the possibility of increasing the violation
of a Bell inequality by making collective measurements. We show that
nonlocality of bipartite pure entangled states, quantified by their maximal
violation of the Bell-Clauser-Horne inequality, can always be enhanced by
collective measurements, even without communication between the parties. For
mixed states we also show that collective measurements can increase the
violation of Bell inequalities, although numerical evidence suggests that the
phenomenon is not common as it is for pure states.
|
[
{
"version": "v1",
"created": "Fri, 7 Apr 2006 01:56:06 GMT"
},
{
"version": "v2",
"created": "Wed, 16 Aug 2006 11:33:48 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Liang",
"Yeong-Cherng",
""
],
[
"Doherty",
"Andrew C.",
""
]
] |
quant-ph/0604046
|
Yury Sherkunov
|
Yury Sherkunov
|
Casimir interaction between excited media in electromagnetic field
| null | null | null | null |
quant-ph
| null |
We investigate the Casimir-Polder interaction between two atoms one of which
is excited. We show that the perturbation theory results in divergence of
integrals for the interaction between an excited atom and a media of dilute
gas. We considered the interaction between two atoms embedded in a dielectric
medium. The non-perturbative method used in this paper shows that the
interaction between the atoms is suppressed due to absorption of photons by the
medium. Now the integrals are divergent no more. Interaction between two media
of dilute gases is considered for the case of high temperatures.
|
[
{
"version": "v1",
"created": "Fri, 7 Apr 2006 09:05:27 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Sherkunov",
"Yury",
""
]
] |
quant-ph/0604047
|
Fabrizio Illuminati
|
S. M. Giampaolo, F. Illuminati, and S. De Siena
|
Characterizing quantum phase transitions by single qubit operations
|
4 pages, 4 figures
| null | null | null |
quant-ph cond-mat.other
| null |
We introduce observable quantities, borrowing from concepts of quantum
information theory, for the characterization of quantum phase transitions in
spin systems. These observables are uniquely defined in terms of single spin
unitary operations. We define the energy gap between the ground state and the
state produced by the action of a single-qubit local gate. We show that this
static quantity involves only single-site expectations and two-point
correlation functions on the ground state. We then discuss a dynamical local
observable defined as the acceleration of quantum state evolution after
performing an instaneous single-qubit perturbation on the ground state. This
quantity involves three-point correlations as well. We show that both the
static and the dynamical observables detect and characterize completely quantum
critical points in a class of spin systems.
|
[
{
"version": "v1",
"created": "Fri, 7 Apr 2006 11:14:08 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Giampaolo",
"S. M.",
""
],
[
"Illuminati",
"F.",
""
],
[
"De Siena",
"S.",
""
]
] |
quant-ph/0604048
|
Mark Whitney
|
Nemanja Isailovic, Yatish Patel, Mark Whitney, John Kubiatowicz
|
Interconnection Networks for Scalable Quantum Computers
|
To appear in International Symposium on Computer Architecture 2006
(ISCA 2006)
| null | null | null |
quant-ph
| null |
We show that the problem of communication in a quantum computer reduces to
constructing reliable quantum channels by distributing high-fidelity EPR pairs.
We develop analytical models of the latency, bandwidth, error rate and resource
utilization of such channels, and show that 100s of qubits must be distributed
to accommodate a single data communication. Next, we show that a grid of
teleportation nodes forms a good substrate on which to distribute EPR pairs. We
also explore the control requirements for such a network. Finally, we propose a
specific routing architecture and simulate the communication patterns of the
Quantum Fourier Transform to demonstrate the impact of resource contention.
|
[
{
"version": "v1",
"created": "Fri, 7 Apr 2006 17:19:56 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Isailovic",
"Nemanja",
""
],
[
"Patel",
"Yatish",
""
],
[
"Whitney",
"Mark",
""
],
[
"Kubiatowicz",
"John",
""
]
] |
quant-ph/0604049
|
Andrew Scott
|
A. J. Scott
|
Tight informationally complete quantum measurements
|
20 pages. Final version
|
J. Phys. A 39, 13507 (2006)
|
10.1088/0305-4470/39/43/009
| null |
quant-ph
| null |
We introduce a class of informationally complete positive-operator-valued
measures which are, in analogy with a tight frame, "as close as possible" to
orthonormal bases for the space of quantum states. These measures are
distinguished by an exceptionally simple state-reconstruction formula which
allows "painless" quantum state tomography. Complete sets of mutually unbiased
bases and symmetric informationally complete positive-operator-valued measures
are both members of this class, the latter being the unique minimal rank-one
members. Recast as ensembles of pure quantum states, the rank-one members are
in fact equivalent to weighted 2-designs in complex projective space. These
measures are shown to be optimal for quantum cloning and linear quantum state
tomography.
|
[
{
"version": "v1",
"created": "Fri, 7 Apr 2006 19:20:28 GMT"
},
{
"version": "v2",
"created": "Sat, 8 Apr 2006 23:19:32 GMT"
},
{
"version": "v3",
"created": "Thu, 6 Jul 2006 21:27:36 GMT"
},
{
"version": "v4",
"created": "Tue, 11 Jul 2006 23:26:08 GMT"
},
{
"version": "v5",
"created": "Tue, 18 Jul 2006 01:22:28 GMT"
},
{
"version": "v6",
"created": "Wed, 11 Oct 2006 03:14:11 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Scott",
"A. J.",
""
]
] |
quant-ph/0604050
|
Otfried Guehne
|
Otfried G\"uhne, Matyas Mechler, Geza Toth, Peter Adam
|
Entanglement criteria based on local uncertainty relations are strictly
stronger than the computable cross norm criterion
|
4 pages, no figure, v2: small changes
|
Phys. Rev. A 74, 010301(R) (2006)
|
10.1103/PhysRevA.74.010301
| null |
quant-ph
| null |
We show that any state which violates the computable cross norm (or
realignment) criterion for separability also violates the separability
criterion of the local uncertainty relations. The converse is not true. The
local uncertainty relations provide a straightforward construction of nonlinear
entanglement witnesses for the cross norm criterion.
|
[
{
"version": "v1",
"created": "Mon, 10 Apr 2006 16:40:39 GMT"
},
{
"version": "v2",
"created": "Thu, 15 Jun 2006 14:26:27 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Gühne",
"Otfried",
""
],
[
"Mechler",
"Matyas",
""
],
[
"Toth",
"Geza",
""
],
[
"Adam",
"Peter",
""
]
] |
quant-ph/0604051
|
Juan Hodelin
|
Juan F. Hodelin, George Khoury, Dirk Bouwmeester
|
Optimal Generation of Pulsed Entangled Photon Pairs
|
8 pages, 6 figures
| null |
10.1103/PhysRevA.74.013802
| null |
quant-ph
| null |
We experimentally investigate a double-pass parametric down-conversion scheme
for producing pulsed, polarization-entangled photon pairs with high visibility.
The amplitudes for creating photon pairs on each pass interfere to compensate
for distinguishing characteristics that normally degrade two-photon visibility.
The result is a high-flux source of polarization-entangled photon pulses that
does not require spectral filtering. We observe quantum interference visibility
of over 95% without the use of spectral filters for 200 femtosecond pulses, and
up to 98.1% with 5 nm bandwidth filters.
|
[
{
"version": "v1",
"created": "Sat, 8 Apr 2006 00:17:21 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Hodelin",
"Juan F.",
""
],
[
"Khoury",
"George",
""
],
[
"Bouwmeester",
"Dirk",
""
]
] |
quant-ph/0604052
|
Dmytro Gavinsky
|
Dmytro Gavinsky
|
On the Role of Shared Entanglement
| null | null | null | null |
quant-ph cs.CC
| null |
Despite the apparent similarity between shared randomness and shared
entanglement in the context of Communication Complexity, our understanding of
the latter is not as good as of the former. In particular, there is no known
"entanglement analogue" for the famous theorem by Newman, saying that the
number of shared random bits required for solving any communication problem can
be at most logarithmic in the input length (i.e., using more than O(log n)
shared random bits would not reduce the complexity of an optimal solution).
In this paper we prove that the same is not true for entanglement. We
establish a wide range of tight (up to a polylogarithmic factor) entanglement
vs. communication tradeoffs for relational problems. The low end is: for any
t>2, reducing shared entanglement from log^t(n) to o(log^{t-2}(n)) qubits can
increase the communication required for solving a problem almost exponentially,
from O(log^t(n)) to \Omega(\sqrt n). The high end is: for any \eps>0, reducing
shared entanglement from n^{1-\eps}log(n) to o(n^{1-\eps}/log(n)) can increase
the required communication from O(n^{1-\eps}log(n)) to
\Omega(n^{1-\eps/2}/log(n)). The upper bounds are demonstrated via protocols
which are exact and work in the \e{simultaneous message passing model}, while
the lower bounds hold for \e{bounded-error protocols}, even in the more
powerful \e{model of 1-way communication}. Our protocols use shared EPR pairs
while the lower bounds apply to any sort of prior entanglement.
We base the lower bounds on a strong direct product theorem for communication
complexity of a certain class of relational problems. We believe that the
theorem might have applications outside the scope of this work.
|
[
{
"version": "v1",
"created": "Sat, 8 Apr 2006 02:44:26 GMT"
},
{
"version": "v2",
"created": "Tue, 22 Aug 2006 06:48:38 GMT"
}
] | 2022-03-29T00:00:00 |
[
[
"Gavinsky",
"Dmytro",
""
]
] |
quant-ph/0604053
|
Ryszard Tana\'s
|
Z. Ficek and R. Tanas
|
Dark periods and revivals of entanglement in a two qubit system
|
4 pages, 3 figures
| null |
10.1103/PhysRevA.74.024304
| null |
quant-ph
| null |
In a recent paper Yu and Eberly [Phys. Rev. Lett. {\bf 93}, 140404 (2004)]
have shown that two initially entangled and afterwards not interacting qubits
can become completely disentangled in a finite time. We study transient
entanglement between two qubits coupled collectively to a multimode vacuum
field and find an unusual feature that the irreversible spontaneous decay can
lead to a revival of the entanglement that has already been destroyed. The
results show that this feature is independent of the coherent dipole-dipole
interaction between the atoms but it depends critically on whether or not the
collective damping is present. We show that the ability of the system to
revival entanglement via spontaneous emission relies on the presence of very
different timescales for the evolution of the populations of the collective
states and coherence between them.
|
[
{
"version": "v1",
"created": "Sat, 8 Apr 2006 13:00:59 GMT"
}
] | 2009-11-13T00:00:00 |
[
[
"Ficek",
"Z.",
""
],
[
"Tanas",
"R.",
""
]
] |
quant-ph/0604054
|
C. F. Huang
|
C. F. Huang and K.-N. Huang
|
On the quantum master equation for fermions
|
25 pages. It is discussed in the revised manuscript how to prove the
trace invariance. Some details are incorporated in the appendixes
| null | null | null |
quant-ph cond-mat.stat-mech
| null |
A quantum master equation is obtained for identical fermions by including a
relaxation term in addition to the mean-field Hamiltonian. [Huang C F and Huang
K N 2004 Chinese J. Phys. ${\bf 42}$ 221; Gebauer R and Car R 2004 Phys. Rev. B
${\bf 70}$ 125324] It is proven in this paper that both the positivity and
Pauli's exclusion principle are preserved under this equation when there exists
an upper bound for the transition rate. Such an equation can be generalized to
model BCS-type quasiparticles, and is reduced to a Markoff master equation of
Lindblad form in the low-density limit with respect to particles or holes.
|
[
{
"version": "v1",
"created": "Sun, 9 Apr 2006 05:30:09 GMT"
},
{
"version": "v2",
"created": "Wed, 11 Oct 2006 13:57:31 GMT"
},
{
"version": "v3",
"created": "Sat, 30 Jun 2007 16:38:34 GMT"
}
] | 2007-06-30T00:00:00 |
[
[
"Huang",
"C. F.",
""
],
[
"Huang",
"K. -N.",
""
]
] |
quant-ph/0604055
|
Yuri I. Ozhigov
|
Y.I.Ozhigov
|
About mathematical apparatus of many body quantum dynamics
|
29 ges, Latex, reference to fond included
| null | null | null |
quant-ph
| null |
We discuss the possibility to modify many-body Hilbert quantum formalism that
is necessary for the representation of quantum systems dynamics. The notion of
effective classical algorithm and visualization of quantum dynamics play the
key role.
|
[
{
"version": "v1",
"created": "Sat, 8 Apr 2006 16:01:43 GMT"
},
{
"version": "v2",
"created": "Thu, 28 Dec 2006 08:25:42 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Ozhigov",
"Y. I.",
""
]
] |
quant-ph/0604056
|
Greg Kuperberg
|
Scott Aaronson and Greg Kuperberg
|
Quantum Versus Classical Proofs and Advice
|
20 pages, now includes a definition of an explicit group that is in
the journal version
|
Theory Comput. 3 (2007), 129-157
| null | null |
quant-ph cs.CC
|
http://arxiv.org/licenses/nonexclusive-distrib/1.0/
|
This paper studies whether quantum proofs are more powerful than classical
proofs, or in complexity terms, whether QMA=QCMA. We prove three results about
this question. First, we give a "quantum oracle separation" between QMA and
QCMA. More concretely, we show that any quantum algorithm needs
$\Omega(\sqrt{2^n/(m+1)})$ queries to find an $n$-qubit "marked state"
$\lvert\psi\rangle$, even if given an $m$-bit classical description of
$\lvert\psi\rangle$ together with a quantum black box that recognizes
$\lvert\psi\rangle$. Second, we give an explicit QCMA protocol that nearly
achieves this lower bound. Third, we show that, in the one previously-known
case where quantum proofs seemed to provide an exponential advantage, classical
proofs are basically just as powerful. In particular, Watrous gave a QMA
protocol for verifying non-membership in finite groups. Under plausible
group-theoretic assumptions, we give a QCMA protocol for the same problem. Even
with no assumptions, our protocol makes only polynomially many queries to the
group oracle. We end with some conjectures about quantum versus classical
oracles, and about the possibility of a classical oracle separation between QMA
and QCMA.
|
[
{
"version": "v1",
"created": "Mon, 10 Apr 2006 02:29:16 GMT"
},
{
"version": "v2",
"created": "Tue, 11 Apr 2006 17:33:49 GMT"
},
{
"version": "v3",
"created": "Thu, 27 Jul 2006 18:21:58 GMT"
},
{
"version": "v4",
"created": "Mon, 28 Sep 2020 21:47:50 GMT"
}
] | 2020-09-30T00:00:00 |
[
[
"Aaronson",
"Scott",
""
],
[
"Kuperberg",
"Greg",
""
]
] |
quant-ph/0604057
|
Alexander Mitin
|
Alexander V. Mitin
|
The analytical solution of the Schr\"{o}dinger equation in
Born-Oppenheimer approximation for $H_2^+$ molecular ion
|
5 pages, 2 figures
| null | null | null |
quant-ph
| null |
An analysis of the analytical solution of the Schr\"{o}dinger equation (which
is a second order differential equation) for $H_2^+$ shows that the second
linear independent solution of this equation is a square integrable function
and therefore the ground state total wave function is a linear combination of
two linear independent wave functions of different space symmetry: cylindrical
and spherical. The wave function of cylindrical symmetry is well known. It has
maxima at the positions of nuclei. The wave function of spherical symmetry and
the corresponding spherical electron distribution, which exists at $R\neq0$ and
locates at the middle of the bond, represents a quasiatom of electron density
of non-nuclear united atom. In the light of the new result the qualitative
behavior of the ground state wave function and the electron density of $H_2^+$
has been reinvestigated. It is shown analytically that a transformation of the
total molecular wave function with two maxima to that one with one maximum
passes through a flat wave function. The presented three-dimension figures of
the electron density visualize the spherical component of the total wave
function and its transformation with increasing internuclear separation.
|
[
{
"version": "v1",
"created": "Sun, 9 Apr 2006 16:35:16 GMT"
}
] | 2007-05-23T00:00:00 |
[
[
"Mitin",
"Alexander V.",
""
]
] |
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