id
stringlengths 9
16
| submitter
stringlengths 1
64
⌀ | authors
stringlengths 3
62.8k
| title
stringlengths 1
382
| comments
stringlengths 1
1.15k
⌀ | journal-ref
stringlengths 1
557
⌀ | doi
stringlengths 7
153
⌀ | report-no
stringlengths 1
509
⌀ | categories
stringlengths 5
125
| license
stringclasses 9
values | abstract
stringlengths 6
6.09k
| versions
listlengths 1
187
| update_date
timestamp[s]date 2007-05-23 00:00:00
2025-04-04 00:00:00
| authors_parsed
listlengths 1
2.83k
|
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
quant-ph/0611058 | Arvind | Geetu Narang and Arvind | Simulating a single qubit channel using a mixed state environment | Published version with minor changes | Phys. Rev. A 75, 032305 (2007) | 10.1103/PhysRevA.75.032305 | null | quant-ph | null | We analyze the class of single qubit channels with the environment modeled by
a one-qubit mixed state. The set of affine transformations for this class of
channels is computed analytically, employing the canonical form for the
two-qubit unitary operator. We demonstrate that, 3/8 of the generalized
depolarizing channels can be simulated by the one-qubit mixed state environment
by explicitly obtaining the shape of the volume occupied by this class of
channels within the tetrahedron representing the generalized depolarizing
channels. Further, as a special case, we show that the two-Pauli Channel cannot
be simulated by a one-qubit mixed state environment.
| [
{
"version": "v1",
"created": "Mon, 6 Nov 2006 05:31:36 GMT"
},
{
"version": "v2",
"created": "Tue, 6 Mar 2007 06:51:24 GMT"
}
]
| 2013-05-29T00:00:00 | [
[
"Narang",
"Geetu",
""
],
[
"Arvind",
"",
""
]
]
|
quant-ph/0611059 | Yi Zhao | Yi Zhao, Bing Qi, and Hoi-Kwong Lo (Center for Quantum Information and
Quantum Control, CQIQC, University of Toronto) | Experimental quantum key distribution with active phase randomization | 3 pages, 3 figures, RevTEX | Appl. Phys. Lett., 90 (4), 044106 (2007) | 10.1063/1.2432296 | null | quant-ph | null | Phase randomization is an important assumption made in many security proofs
of practical quantum key distribution (QKD) systems. Here, we present the first
experimental demonstration of QKD with reliable active phase randomization. One
key contribution is a polarization-insensitive phase modulator, which we added
to a commercial phase-coding QKD system to randomize the global phase of each
bit. We also proposed a simple but useful method to verify experimentally that
the phase is indeed randomized. Our result shows very low QBER (<1%). We expect
this active phase randomization process to be a standard part in future QKD
set-ups due to its significance and feasibility.
| [
{
"version": "v1",
"created": "Mon, 6 Nov 2006 05:56:16 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Zhao",
"Yi",
"",
"Center for Quantum Information and\n Quantum Control, CQIQC, University of Toronto"
],
[
"Qi",
"Bing",
"",
"Center for Quantum Information and\n Quantum Control, CQIQC, University of Toronto"
],
[
"Lo",
"Hoi-Kwong",
"",
"Center for Quantum Information and\n Quantum Control, CQIQC, University of Toronto"
]
]
|
quant-ph/0611060 | Arpita Maitra | Arpita Maitra | Some Possibility and Impossibility Results related to Discrete Fourier
type transforms in Quantum Information | This paper has been revised a lot in further works. The duly revised
and published version is available at
http://iopscience.iop.org/0256-307X/29/3/030303/ | null | null | null | quant-ph | null | Very recently the most general ensemble of qubits are identified using the
notion of linearity; any of these qubits gets accepted by a Hadamard gate to
generate the equal superposition of the qubit and its orthogonal. Towards more
generalization, we investigate the possibility and impossibility results
related to Discrete Fourier Transform (DFT) type of operations for a more
general set up of qutrits.
| [
{
"version": "v1",
"created": "Mon, 6 Nov 2006 06:53:23 GMT"
},
{
"version": "v2",
"created": "Sun, 26 Aug 2012 10:36:42 GMT"
}
]
| 2012-08-28T00:00:00 | [
[
"Maitra",
"Arpita",
""
]
]
|
quant-ph/0611061 | Afshin Shafiee Dr. | Afshin Shafiee and Majid Karimi | On the relationship between entropy and information | 15 pages, 2 figures. The content of paper is improved throughly in
the second version | null | 10.4006/1.3153419 | null | quant-ph | null | In this paper, we analyze the relationship between entropy and information in
the context of the mixing process of two identical ideal gases. We will argue
that entropy has a special information-based feature that is enfolded in the
statistical entropy, but the second law does not include it directly.
Therefore, in some given processes in thermodynamics where there is no matter
and energy interaction between the system and environment, the state of the
system may go towards a situation of lower probability to increase observer's
information in environment. This is a kind of an information-based interaction
in which the total entropy is not constrained by the second law.
| [
{
"version": "v1",
"created": "Mon, 6 Nov 2006 08:32:36 GMT"
},
{
"version": "v2",
"created": "Mon, 10 Sep 2007 14:16:28 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Shafiee",
"Afshin",
""
],
[
"Karimi",
"Majid",
""
]
]
|
quant-ph/0611062 | Roland Doll | Roland Doll and Gert-Ludwig Ingold | Lissajous curves and semiclassical theory: The two-dimensional harmonic
oscillator | 9 pages, 3 figures; to appear in Am. J. Phys | Am. J. Phys. 75, 208 (2007) | 10.1119/1.2402157 | null | quant-ph | null | The semiclassical treatment of the two-dimensional harmonic oscillator
provides an instructive example of the relation between classical motion and
the quantum mechanical energy spectrum. We extend previous work on the
anisotropic oscillator with incommensurate frequencies and the isotropic
oscillator to the case with commensurate frequencies for which the Lissajous
curves appear as classical periodic orbits. Because of the three different
scenarios depending on the ratio of its frequencies, the two-dimensional
harmonic oscillator offers a unique way to explicitly analyze the role of
symmetries in classical and quantum mechanics.
| [
{
"version": "v1",
"created": "Mon, 6 Nov 2006 11:54:06 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Doll",
"Roland",
""
],
[
"Ingold",
"Gert-Ludwig",
""
]
]
|
quant-ph/0611063 | Metod Saniga | Metod Saniga (ASTRINSTSAV), Michel Planat (FEMTO-ST), Petr Pracna
(JH-Inst) | Projective Ring Line Encompassing Two-Qubits | 8 pages, three tables; Version 2 - a few typos and one discrepancy
corrected; Version 3: substantial extension of the paper - two-qubits are
generalized quadrangles of order two; Version 4: self-dual picture completed;
Version 5: intriguing triality found -- three kinds of geometric hyperplanes
within GQ and three distinguished subsets of Pauli operators | Theoretical and Mathematical Physics 155, 3 (2008) 905-913 | 10.1007/s11232-008-0076-x | null | quant-ph | null | The projective line over the (non-commutative) ring of two-by-two matrices
with coefficients in GF(2) is found to fully accommodate the algebra of 15
operators - generalized Pauli matrices - characterizing two-qubit systems. The
relevant sub-configuration consists of 15 points each of which is either
simultaneously distant or simultaneously neighbor to (any) two given distant
points of the line. The operators can be identified with the points in such a
one-to-one manner that their commutation relations are exactly reproduced by
the underlying geometry of the points, with the ring geometrical notions of
neighbor/distant answering, respectively, to the operational ones of
commuting/non-commuting. This remarkable configuration can be viewed in two
principally different ways accounting, respectively, for the basic 9+6 and 10+5
factorizations of the algebra of the observables. First, as a disjoint union of
the projective line over GF(2) x GF(2) (the "Mermin" part) and two lines over
GF(4) passing through the two selected points, the latter omitted. Second, as
the generalized quadrangle of order two, with its ovoids and/or spreads
standing for (maximum) sets of five mutually non-commuting operators and/or
groups of five maximally commuting subsets of three operators each. These
findings open up rather unexpected vistas for an algebraic geometrical
modelling of finite-dimensional quantum systems and give their numerous
applications a wholly new perspective.
| [
{
"version": "v1",
"created": "Mon, 6 Nov 2006 12:33:33 GMT"
},
{
"version": "v2",
"created": "Mon, 13 Nov 2006 14:11:35 GMT"
},
{
"version": "v3",
"created": "Tue, 5 Dec 2006 13:45:02 GMT"
},
{
"version": "v4",
"created": "Mon, 11 Dec 2006 13:19:35 GMT"
},
{
"version": "v5",
"created": "Thu, 28 Dec 2006 19:48:56 GMT"
}
]
| 2008-06-26T00:00:00 | [
[
"Saniga",
"Metod",
"",
"ASTRINSTSAV"
],
[
"Planat",
"Michel",
"",
"FEMTO-ST"
],
[
"Pracna",
"Petr",
"",
"JH-Inst"
]
]
|
quant-ph/0611064 | Irina Dobrovolska | I. V. Dobrovolska, R. S. Tutik | Perturbation theory for sextic doubly anharmonic oscillator | null | null | null | null | quant-ph | null | A simple method for the calculation of higher orders of the logarithmic
perturbation theory for bound states of the spherical anharmonic oscillator is
developed. The structure of the perturbation series for energy eigenvalues of
the sextic doubly anharmonic oscillator is investigated. The recursion
technique for deriving renormalized perturbation expansions is offered.
| [
{
"version": "v1",
"created": "Mon, 6 Nov 2006 19:28:25 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Dobrovolska",
"I. V.",
""
],
[
"Tutik",
"R. S.",
""
]
]
|
quant-ph/0611065 | Ramazan Sever | Sameer M. Ikhdair and Ramazan Sever | Exact Polynomial Solutions of the Mie-Type Potential in the
N-Dimensional Schrodinger Equation | 10 pages | J. Mol. Struc(Theochem) 855, 13(2008) | null | null | quant-ph | null | The polynomial solution of the N-dimensional space Schrodinger equation for a
special case of Mie potential is obtained for any arbitrary $% l-state. The
exact bound-state energy eigenvalues and the corresponding eigenfunctions are
calculated for diatomic molecular systems in the Mie-type potential. Keywords:
Mie potential, Schrodinger equation, Eigenvalue, Eigenfunction, Diatomic
molecules
| [
{
"version": "v1",
"created": "Mon, 6 Nov 2006 13:42:59 GMT"
}
]
| 2008-07-15T00:00:00 | [
[
"Ikhdair",
"Sameer M.",
""
],
[
"Sever",
"Ramazan",
""
]
]
|
quant-ph/0611066 | Candadi Sukumar Dr. | C. V. Sukumar | Sum rules for Confining Potentials | 16 pages. Some typographical mistakes are corrected in the latest
version | null | null | null | quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Using the Green's function associated with the one-dimensional Schroedinger
equation it is possible to establish a hierarchy of sum rules involving the
eigenvalues of confining potentials which have only a boundstate spectrum. For
some potentials the sum rules could lead to divergences. It is shown that when
this happens it is possible to examine the separate sum rules satisfied by the
even and odd eigenstates of a symmetric confining potential and by subtraction
cancel the divergences exactly and produce a new sum rule which is free of
divergences. The procedure is illustrated by considering symmetric power law
potentials and the use of several examples. One of the examples considered
shows that the zeros of the Airy function and its derivative obey a sum rule
and this sum rule is verified. It is also shown how the procedure may be
generalised to establish sum rules for arbitrary symmetric confining
potentials.
| [
{
"version": "v1",
"created": "Mon, 6 Nov 2006 15:03:21 GMT"
},
{
"version": "v2",
"created": "Thu, 18 Oct 2012 19:49:58 GMT"
},
{
"version": "v3",
"created": "Mon, 22 Oct 2012 19:43:30 GMT"
},
{
"version": "v4",
"created": "Thu, 13 Sep 2018 12:19:27 GMT"
}
]
| 2018-09-14T00:00:00 | [
[
"Sukumar",
"C. V.",
""
]
]
|
quant-ph/0611067 | Kurt Jacobs | Kurt Jacobs, Daniel A. Steck | A Straightforward Introduction to Continuous Quantum Measurement | 24 pages, 3 eps figues. To appear in Contemporary Physics | Contemporary Physics 47, 279 (2006) | 10.1080/00107510601101934 | null | quant-ph | null | We present a pedagogical treatment of the formalism of continuous quantum
measurement. Our aim is to show the reader how the equations describing such
measurements are derived and manipulated in a direct manner. We also give
elementary background material for those new to measurement theory, and
describe further various aspects of continuous measurements that should be
helpful to those wanting to use such measurements in applications.
Specifically, we use the simple and direct approach of generalized measurements
to derive the stochastic master equation describing the continuous measurements
of observables, give a tutorial on stochastic calculus, treat multiple
observers and inefficient detection, examine a general form of the measurement
master equation, and show how the master equation leads to information gain and
disturbance. To conclude, we give a detailed treatment of imaging the resonance
fluorescence from a single atom as a concrete example of how a continuous
position measurement arises in a physical system.
| [
{
"version": "v1",
"created": "Mon, 6 Nov 2006 22:22:29 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Jacobs",
"Kurt",
""
],
[
"Steck",
"Daniel A.",
""
]
]
|
quant-ph/0611068 | Ratna Koley | Ratna Koley, Sayan Kar | Exact bound states in volcano potentials | 10 pages, 6 figures, to appear in Phys. Lett. A | Phys.Lett.A363:369-373,2007 | 10.1016/j.physleta.2006.11.031 | null | quant-ph hep-th | null | Quantum mechanics in a one--parameter family of volcano potentials is
investigated. After a discussion on their construction and classical mechanics,
we obtain exact, normalisable bound states for specific values of the energy.
The nature of the wave functions and probability densities, as well as some
curious features of the solutions are highlighted.
| [
{
"version": "v1",
"created": "Tue, 7 Nov 2006 04:37:24 GMT"
},
{
"version": "v2",
"created": "Mon, 4 Dec 2006 09:37:26 GMT"
}
]
| 2008-11-26T00:00:00 | [
[
"Koley",
"Ratna",
""
],
[
"Kar",
"Sayan",
""
]
]
|
quant-ph/0611069 | Milos V. Lokajicek | Milos V. Lokajicek | Physical theory of the twentieth century and contemporary philosophy | 12 pages | null | 10.2478/v10005-007-0012-0 | null | quant-ph | null | It has been shown that the criticism of Pauli as well as of Susskind and
Glogover may be avoided if the standard quantum-mechanical mathematical model
has been suitably extended. There is not more any reason for Einstein's
citicism, either, if in addition to some new results concerning Bell's
inequalities and Belifante's argument are taken into account. The ensemble
interpretation of quantum mechanics (or the hidden-variable theory) should be
preferred, which is also supported by the already published results of
experiments with three polarizers. Greater space in the text has been devoted
also to the discussion of epistemological problems and some philosophical
consequences.
| [
{
"version": "v1",
"created": "Tue, 7 Nov 2006 11:10:34 GMT"
},
{
"version": "v2",
"created": "Thu, 9 Nov 2006 08:49:39 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Lokajicek",
"Milos V.",
""
]
]
|
quant-ph/0611070 | Giulio Chiribella | F. Buscemi, G. Chiribella, and G. M. D'Ariano | Quantum erasure of decoherence | 10 pages, 1 figure | Open Sys. & Information Dyn. 14, 53 (2007) | 10.1007/s11080-007-9028-4 | null | quant-ph | null | We consider the classical algebra of observables that are diagonal in a given
orthonormal basis, and define a complete decoherence process as a completely
positive map that asymptotically converts any quantum observable into a
diagonal one, while preserving the elements of the classical algebra. For
quantum systems in dimension two and three any decoherence process can be
undone by collecting classical information from the environment and using such
an information to restore the initial system state. As a relevant example, we
illustrate the quantum eraser of Scully et al. [Nature 351, 111 (1991)] as an
example of environment-assisted correction. Moreover, we present the
generalization of the eraser setup for d-dimensional systems, showing that any
von Neumann measurement on a system can be undone by a complementary
measurement on the environment.
| [
{
"version": "v1",
"created": "Tue, 7 Nov 2006 10:12:37 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Buscemi",
"F.",
""
],
[
"Chiribella",
"G.",
""
],
[
"D'Ariano",
"G. M.",
""
]
]
|
quant-ph/0611071 | Joerg Evers | M. Kiffner, J. Evers, and C. H. Keitel | Breakdown of the few-level approximation in collective systems | null | Phys. Rev. A 76, 013807 (2007) | 10.1103/PhysRevA.76.013807 | null | quant-ph | null | The validity of the few-level approximation in dipole-dipole interacting
collective systems is discussed. As example system, we study the archetype case
of two dipole-dipole interacting atoms, each modelled by two complete sets of
angular momentum multiplets. We establish the breakdown of the few-level
approximation by first proving the intuitive result that the dipole-dipole
induced energy shifts between collective two-atom states depend on the length
of the vector connecting the atoms, but not on its orientation, if complete and
degenerate multiplets are considered. A careful analysis of our findings
reveals that the simplification of the atomic level scheme by artificially
omitting Zeeman sublevels in a few-level approximation generally leads to
incorrect predictions. We find that this breakdown can be traced back to the
dipole-dipole coupling of transitions with orthogonal dipole moments. Our
interpretation enables us to identify special geometries in which partial
few-level approximations to two- or three-level systems are valid.
| [
{
"version": "v1",
"created": "Tue, 7 Nov 2006 11:06:23 GMT"
},
{
"version": "v2",
"created": "Mon, 4 Jun 2007 12:39:54 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Kiffner",
"M.",
""
],
[
"Evers",
"J.",
""
],
[
"Keitel",
"C. H.",
""
]
]
|
quant-ph/0611072 | Sandro Sozzo | Claudio Garola, Sandro Sozzo | On the Physical Interpretation of Partial Traces: Two Nonstandard
Viewpoints | Revised Introduction. Minor changes in the abstract and in Secs. 2-5 | Theoretical and Mathematical Physics, 152(2): 1087-1098 (2007) | 10.1007/s11232-007-0093-1 | null | quant-ph | null | Mixed states are introduced in physics in order to express our ignorance
about the actual state of a physical system and are represented in standard
quantum mechanics (QM) by density operators. Such operators also appear if one
considers a (pure) entangled state of a compound system $\Omega$ and performs
partial traces on the projection operator representing it. Yet, they do not
represent mixed states (or proper mixtures) of the subsystems in this case, but
improper mixtures, since the coefficients in the convex sums expressing them
never bear the ignorance interpretation. Hence, one cannot attribute states to
the subsystems of a compound physical system in QM (subentity problem). We
discuss here two alternative proposals that can be worked out within the
Brussels and Lecce approaches. We firstly summarize the general framework
provided by the former, which suggests that improper mixtures could be
considered as new pure states. Then, we show that improper mixtures can be
considered as true (yet nonpure) states also according to the latter. The two
proposals seem to be compatible notwithstanding their different terminologies.
| [
{
"version": "v1",
"created": "Tue, 7 Nov 2006 14:32:23 GMT"
},
{
"version": "v2",
"created": "Fri, 24 Nov 2006 12:15:15 GMT"
}
]
| 2014-11-13T00:00:00 | [
[
"Garola",
"Claudio",
""
],
[
"Sozzo",
"Sandro",
""
]
]
|
quant-ph/0611073 | Kristian Rymann Hansen | Kristian Rymann Hansen and Klaus Molmer | Stationary light pulses in ultra cold atomic gasses | 4 pages, 3 figures | null | null | null | quant-ph | null | We present a theoretical treatment of electromagnetically induced
transparency and light storage using standing wave coupling fields in a medium
comprised of stationary atoms, such as an ultra cold atomic gas or a solid
state medium. We show that it is possible to create stationary pulses of light
which have a qualitatively different behavior than in the case of a thermal gas
medium, offering greater potential for quantum information processing
applications.
| [
{
"version": "v1",
"created": "Tue, 7 Nov 2006 14:41:32 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Hansen",
"Kristian Rymann",
""
],
[
"Molmer",
"Klaus",
""
]
]
|
quant-ph/0611074 | Marcin Wie\'sniak | Marcin Wiesniak, Marek Zukowski | Analysis of critical parameters in the scheme of Bj\"ork, Jonsson, and
S\'anchez-Soto | 7 pages, 3 figures | null | null | null | quant-ph | null | Bj\"ork, Jonsson, and S\'anchez-Soto describe an interesting
(gedanken-)experiment which demonstrates that single photons can indeed lead to
effects which have no local realistic description. %It is one of few cases
where the experimental falsification of the conjecture of local realism has
been done with use of the CH inequality, rather that the CHSH inequality. We
study the critical values of parameters of some possible features of a
non-perfect realisation of the experiment (especially photon loss, which could
be looked at as the detection efficiency), that need to be satisfied so that
the experiment can be considered as a valid test of quantum mechanics versus
local realism. Interestingly, the scheme turns out to be robust against photon
loss.
| [
{
"version": "v1",
"created": "Tue, 7 Nov 2006 15:47:18 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Wiesniak",
"Marcin",
""
],
[
"Zukowski",
"Marek",
""
]
]
|
quant-ph/0611075 | Simone Severini | Lieven Clarisse, Sibasish Ghosh, Simone Severini, Anthony Sudbery | The disentangling power of unitaries | 2 pages; Addendum to quant-ph/0502040 | null | 10.1016/j.physleta.2007.02.001 | null | quant-ph | null | We define the disentangling power of a unitary operator in a similar way as
the entangling power defined by Zanardi, Zalka and Faoro [PRA, 62, 030301]. A
general formula is derived and it is shown that both quantities are directly
proportional. All results concerning the entangling power can simply be
translated into similar statements for the disentangling power. In particular,
the disentangling power is maximal for certain permutations derived from
orthogonal latin squares. These permutations can therefore be interpreted as
those that distort entanglement in a maximal way.
| [
{
"version": "v1",
"created": "Tue, 7 Nov 2006 16:09:15 GMT"
},
{
"version": "v2",
"created": "Thu, 9 Nov 2006 18:14:04 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Clarisse",
"Lieven",
""
],
[
"Ghosh",
"Sibasish",
""
],
[
"Severini",
"Simone",
""
],
[
"Sudbery",
"Anthony",
""
]
]
|
quant-ph/0611076 | Olaf Dreyer | Olaf Dreyer | Classicality in Quantum Mechanics | Converence talk presented at DICE 2006 in Piombino. To be published
in the Journal of Physics: Conference Series | J.Phys.Conf.Ser.67:012051,2007 | 10.1088/1742-6596/67/1/012051 | null | quant-ph | null | In this article we propose a solution to the measurement problem in quantum
mechanics. We point out that the measurement problem can be traced to an a
priori notion of classicality in the formulation of quantum mechanics. If this
notion of classicality is dropped and instead classicality is defined in purely
quantum mechanical terms the measurement problem can be avoided. We give such a
definition of classicality. It identifies classicality as a property of large
quantum system. We show how the probabilistic nature of quantum mechanics is a
result of this notion of classicality. We also comment on what the implications
of this view are for the search of a quantum theory of gravity.
| [
{
"version": "v1",
"created": "Tue, 7 Nov 2006 17:24:17 GMT"
}
]
| 2008-11-26T00:00:00 | [
[
"Dreyer",
"Olaf",
""
]
]
|
quant-ph/0611077 | Dimitris Tsomokos Dr | D.I. Tsomokos, M.J. Hartmann, S.F. Huelga, M.B. Plenio | Entanglement dynamics in chains of qubits with noise and disorder | 17 pages, 9 figures (replaced with published version: updated
references, minor changes and typos) | New Journal of Physics 9, 79 (2007) | 10.1088/1367-2630/9/3/079 | null | quant-ph cond-mat.other | null | The entanglement dynamics of arrays of qubits is analysed in the presence of
some general sources of noise and disorder. In particular, we consider linear
chains of Josephson qubits in experimentally realistic conditions.
Electromagnetic and other (spin or boson) fluctuations due to the background
circuitry and surrounding substrate, finite temperature in the external
environment, and disorder in the initial preparation and the control parameters
are embedded into our model. We show that the amount of disorder that is
typically present in current experiments does not affect the entanglement
dynamics significantly, while the presence of noise can have a drastic
influence on the generation and propagation of entanglement. We examine under
which circumstances the system exhibits steady-state entanglement for both
short (N < 10) and long (N > 30) chains and show that, remarkably, there are
parameter regimes where the steady-state entanglement is strictly non-monotonic
as a function of the noise strength. We also present optimized schemes for
entanglement verification and quantification based on simple correlation
measurements that are experimentally more economic than state tomography.
| [
{
"version": "v1",
"created": "Tue, 7 Nov 2006 17:45:31 GMT"
},
{
"version": "v2",
"created": "Sat, 31 Mar 2007 07:22:54 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Tsomokos",
"D. I.",
""
],
[
"Hartmann",
"M. J.",
""
],
[
"Huelga",
"S. F.",
""
],
[
"Plenio",
"M. B.",
""
]
]
|
quant-ph/0611078 | Vivian Franca V. V. Franca | V. V. Fran\c{c}a and G. A. Prataviera | Stability and entanglement in optical-atomic amplification of trapped
atoms: the role of atomic collisions | 6 pages, 4 figures, accepted by PRA | Phys. Rev. A 75, 043604 (2007) | 10.1103/PhysRevA.75.043604 | null | quant-ph cond-mat.other cond-mat.stat-mech physics.atom-ph | null | Atomic collisions are included in an interacting system of optical fields and
trapped atoms allowing field amplification. We study the effects of collisions
on the system stability. Also a study of the degree of entanglement between
atomic and optical fields is made. We found that, for an atomic field initially
in a vacuum state and optical field in a coherent state, the degree of
entanglement does not depend on the optical field intensity or phase. We show
that in conditions of exponential instability the system presents at long times
two distinct stationary degree of entanglement with collisions affecting only
one of them.
| [
{
"version": "v1",
"created": "Tue, 7 Nov 2006 17:47:43 GMT"
},
{
"version": "v2",
"created": "Wed, 21 Mar 2007 19:13:15 GMT"
}
]
| 2008-06-17T00:00:00 | [
[
"França",
"V. V.",
""
],
[
"Prataviera",
"G. A.",
""
]
]
|
quant-ph/0611079 | Cosmo Lupo | Cosmo Lupo, Paolo Aniello, Mario Napolitano, Giuseppe Florio | Robustness against parametric noise of non ideal holonomic gates | 8 pages, 8 figures, several changes made, accepted for publication on
Phys. Rev. A | Phys. Rev. A 76, 012309 (2007) | 10.1103/PhysRevA.76.012309 | null | quant-ph | null | Holonomic gates for quantum computation are commonly considered to be robust
against certain kinds of parametric noise, the very motivation of this
robustness being the geometric character of the transformation achieved in the
adiabatic limit. On the other hand, the effects of decoherence are expected to
become more and more relevant when the adiabatic limit is approached. Starting
from the system described by Florio et al. [Phys. Rev. A 73, 022327 (2006)],
here we discuss the behavior of non ideal holonomic gates at finite operational
time, i.e., far before the adiabatic limit is reached. We have considered
several models of parametric noise and studied the robustness of finite time
gates. The obtained results suggest that the finite time gates present some
effects of cancellation of the perturbations introduced by the noise which
mimic the geometrical cancellation effect of standard holonomic gates.
Nevertheless, a careful analysis of the results leads to the conclusion that
these effects are related to a dynamical instead of geometrical feature.
| [
{
"version": "v1",
"created": "Tue, 7 Nov 2006 18:50:54 GMT"
},
{
"version": "v2",
"created": "Wed, 9 May 2007 17:08:30 GMT"
}
]
| 2007-07-19T00:00:00 | [
[
"Lupo",
"Cosmo",
""
],
[
"Aniello",
"Paolo",
""
],
[
"Napolitano",
"Mario",
""
],
[
"Florio",
"Giuseppe",
""
]
]
|
quant-ph/0611080 | Robin Blume-Kohout | Robin Blume-Kohout | Optimal, reliable estimation of quantum states | RevTeX; 14 pages, 2 embedded figures. Comments enthusiastically
welcomed! | New J. Phys. 12, 043034 (2010) | 10.1088/1367-2630/12/4/043034 | null | quant-ph | null | Accurately inferring the state of a quantum device from the results of
measurements is a crucial task in building quantum information processing
hardware. The predominant state estimation procedure, maximum likelihood
estimation (MLE), generally reports an estimate with zero eigenvalues. These
cannot be justified. Furthermore, the MLE estimate is incompatible with error
bars, so conclusions drawn from it are suspect. I propose an alternative
procedure, Bayesian mean estimation (BME). BME never yields zero eigenvalues,
its eigenvalues provide a bound on their own uncertainties, and it is the most
accurate procedure possible. I show how to implement BME numerically, and how
to obtain natural error bars that are compatible with the estimate. Finally, I
briefly discuss the differences between Bayesian and frequentist estimation
techniques.
| [
{
"version": "v1",
"created": "Tue, 7 Nov 2006 21:03:31 GMT"
}
]
| 2010-05-04T00:00:00 | [
[
"Blume-Kohout",
"Robin",
""
]
]
|
quant-ph/0611081 | Somshubhro Bandyopadhyay | Somshubhro Bandyopadhyay, Vwani Roychowdhury | Superadditivity of distillable entanglement From Quantum Teleportation | 4 pages, 4 figures | Phys. Rev. A 72, 060303(R) (2005) | 10.1103/PhysRevA.72.060303 | null | quant-ph | null | We show that the phenomenon of superadditivity of distillable entanglement
observed in multipartite quantum systems results from the consideration of
states created during the execution of the standard end-to-end quantum
teleportation protocol (and a few additional local operations and classical
communication (LOCC) steps) on a linear chain of singlets. Some of these
intermediate states are tensor products of bound-entangled (BE) states, and
hence, by construction possess distillable entanglement, which can be unlocked
by simply completing the rest of the LOCC operations required by the underlying
teleportation protocol. We use this systematic approach to construct both new
and known examples of superactivation of bound entanglement, and first examples
of activation of BE states using other BE states. A surprising outcome is the
construction of noiseless quantum relay channels with no distillable
entanglement between any two parties, except for that between the two end
nodes.
| [
{
"version": "v1",
"created": "Tue, 7 Nov 2006 21:43:40 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Bandyopadhyay",
"Somshubhro",
""
],
[
"Roychowdhury",
"Vwani",
""
]
]
|
quant-ph/0611082 | Constantin Bachas | C.P. Bachas | Comment on the sign of the Casimir force | 13 pages, 1 figure, Latex file. Several points clarified and
expanded, two references added. | J.Phys.A40:9089-9096,2007 | 10.1088/1751-8113/40/30/028 | null | quant-ph hep-th | null | I show that reflection positivity implies that the force between any mirror
pair of charge-conjugate probes of the quantum vacuum is attractive. This
generalizes a recent theorem of Kenneth and Klich to interacting quantum
fields, to arbitrary semiclassical bodies, and to quantized probes with
non-overlapping wavefunctions. I also prove that the torques on
charge-conjugate probes tend always to rotate them into a mirror-symmetric
position.
| [
{
"version": "v1",
"created": "Wed, 8 Nov 2006 09:21:56 GMT"
},
{
"version": "v2",
"created": "Mon, 11 Dec 2006 17:56:01 GMT"
},
{
"version": "v3",
"created": "Tue, 3 Apr 2007 18:02:23 GMT"
}
]
| 2008-11-26T00:00:00 | [
[
"Bachas",
"C. P.",
""
]
]
|
quant-ph/0611083 | Marcin Wie\'sniak | Marcin Wiesniak, Piotr Badziag, Marek Zukowski | Explicit form of correlation function three-settings tight Bell
inequalities for three qubits | 8 pages, no figures, | null | 10.1103/PhysRevA.76.012110 | null | quant-ph | null | We present a method to derive explicit forms of tight correlation function
Bell inequalities for three systems and dichotomic observables, which involve
three settings for each observer. We also give sufficient conditions for
quantum predictions to satisfy the new inequalities.
| [
{
"version": "v1",
"created": "Wed, 8 Nov 2006 15:27:15 GMT"
},
{
"version": "v2",
"created": "Thu, 3 May 2007 19:13:00 GMT"
},
{
"version": "v3",
"created": "Fri, 7 Mar 2008 05:16:03 GMT"
}
]
| 2008-03-07T00:00:00 | [
[
"Wiesniak",
"Marcin",
""
],
[
"Badziag",
"Piotr",
""
],
[
"Zukowski",
"Marek",
""
]
]
|
quant-ph/0611084 | Joerg Evers | M. Kiffner, J. Evers, and C. H. Keitel | Coherent control in a decoherence-free subspace of a collective
multi-level system | 15 pages, 11 figures | Phys. Rev. A 75, 032313 (2007) | 10.1103/PhysRevA.75.032313 | null | quant-ph | null | Decoherence-free subspaces (DFS) in systems of dipole-dipole interacting
multi-level atoms are investigated theoretically. It is shown that the
collective state space of two dipole-dipole interacting four-level atoms
contains a four-dimensional DFS. We describe a method that allows to populate
the antisymmetric states of the DFS by means of a laser field, without the need
of a field gradient between the two atoms. We identify these antisymmetric
states as long-lived entangled states. Further, we show that any single-qubit
operation between two states of the DFS can be induced by means of a microwave
field. Typical operation times of these qubit rotations can be significantly
shorter than for a nuclear spin system.
| [
{
"version": "v1",
"created": "Wed, 8 Nov 2006 12:28:31 GMT"
},
{
"version": "v2",
"created": "Mon, 4 Jun 2007 12:26:44 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Kiffner",
"M.",
""
],
[
"Evers",
"J.",
""
],
[
"Keitel",
"C. H.",
""
]
]
|
quant-ph/0611085 | Yao Cheng | Yao Cheng, Bing Xia, Chuanxiang Tang, Yinong Liu, Qingxiu Jin | Generation of Long-Lived Isomeric States via Bremsstrahlung Irradiation | ICAME 05 conference report | Hyperfine Interactions Vol.167, 833-838(2006) | 10.1007/s10751-006-9368-4 | null | quant-ph physics.atom-ph | null | A method to generate long-lived isomeric states effectively for Mossbauer
applications is reported. We demonstrate that this method is better and easier
to provide highly sensitive Mossbauer effect of long-lived isomers (>1ms) such
as 103Rh. Excitation of (gamma,gamma) process by synchrotron radiation is
painful due mainly to their limited linewidth. Instead,(gamma,gamma') process
of bremsstrahlung excitation is applied to create these long-lived isomers.
Isomers of 45Sc, 107Ag, 109Ag, and 103Rh have been generated from this method.
Among them, 103Rh is the only one that we have obtained the gravitational
effect at room temperature.
| [
{
"version": "v1",
"created": "Wed, 8 Nov 2006 13:22:53 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Cheng",
"Yao",
""
],
[
"Xia",
"Bing",
""
],
[
"Tang",
"Chuanxiang",
""
],
[
"Liu",
"Yinong",
""
],
[
"Jin",
"Qingxiu",
""
]
]
|
quant-ph/0611086 | Marek Zukowski | Marek Zukowski | All tight multipartite Bell correlation inequalities for three
dichotomic observables per observer | 10 pages, RevTeX | null | null | null | quant-ph | null | A derivation of the full set of Bell inequalities involving correlation
functions, for two parties, with binary observables, and three possible local
settings. The procedure can be extended straightforwardly to multiparty
correlations.
| [
{
"version": "v1",
"created": "Wed, 8 Nov 2006 14:40:50 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Zukowski",
"Marek",
""
]
]
|
quant-ph/0611087 | Ulrike Herzog | Ulrike Herzog | Optimum unambiguous discrimination of two mixed states and application
to a class of similar states | 8 pages, changes in title and presentation | null | 10.1103/PhysRevA.75.052309 | null | quant-ph | null | We study the measurement for the unambiguous discrimination of two mixed
quantum states that are described by density operators $\rho_1$ and $\rho_2$ of
rank d, the supports of which jointly span a 2d-dimensional Hilbert space.
Based on two conditions for the optimum measurement operators, and on a
canonical representation for the density operators of the states, two equations
are derived that allow the explicit construction of the optimum measurement,
provided that the expression for the fidelity of the states has a specific
simple form. For this case the problem is mathematically equivalent to
distinguishing pairs of pure states, even when the density operators are not
diagonal in the canonical representation. The equations are applied to the
optimum unambiguous discrimination of two mixed states that are similar states,
given by $\rho_2= U\rho_1 U^{\dag}$, and that belong to the class where the
unitary operator U can be decomposed into multiple rotations in the d mutually
orthogonal two-dimensional subspaces determined by the canonical
representation.
| [
{
"version": "v1",
"created": "Wed, 8 Nov 2006 16:26:09 GMT"
},
{
"version": "v2",
"created": "Tue, 14 Nov 2006 20:47:53 GMT"
},
{
"version": "v3",
"created": "Mon, 12 Mar 2007 17:52:49 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Herzog",
"Ulrike",
""
]
]
|
quant-ph/0611088 | Hui Jing | Hui Jing and Jing Cheng | Quantum superchemistry in an output coupler of coherent matter waves | 3 figures, accepted by Phys.Rev.A (submitted to prl in July,
transferred to pra in Sep. and accepted in Nov.) | null | 10.1103/PhysRevA.74.063607 | null | quant-ph | null | We investigate the quantum superchemistry or Bose-enhanced atom-molecule
conversions in a coherent output coupler of matter waves, as a simple
generalization of the two-color photo-association. The stimulated effects of
molecular output step and atomic revivals are exhibited by steering the rf
output couplings. The quantum noise-induced molecular damping occurs near a
total conversion in a levitation trap. This suggests a feasible two-trap scheme
to make a stable coherent molecular beam.
| [
{
"version": "v1",
"created": "Wed, 8 Nov 2006 17:39:49 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Jing",
"Hui",
""
],
[
"Cheng",
"Jing",
""
]
]
|
quant-ph/0611089 | Romain All\'eaume | Rex A. C. Medeiros (UCG Brazil), Francisco M. De Assis (UCG Brazil) | Quantum Zero-error Capacity | Published in the International Journal of Quantum Informaton | null | null | null | quant-ph | null | We define here a new kind of quantum channel capacity by extending the
concept of zero-error capacity for a noisy quantum channel. The necessary
requirement for which a quantum channel has zero-error capacity greater than
zero is given. Finally, we point out some directions on how to calculate the
zero-error capacity of such channels.
| [
{
"version": "v1",
"created": "Wed, 8 Nov 2006 17:47:10 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Medeiros",
"Rex A. C.",
"",
"UCG Brazil"
],
[
"De Assis",
"Francisco M.",
"",
"UCG Brazil"
]
]
|
quant-ph/0611090 | Miguel Orszag | D.Mundarain, M.Orszag | Decoherence Free Subspace and entanglement by interaction with a common
squeezed bath | 4 pages, 1 figure | null | 10.1103/PhysRevA.75.040303 | null | quant-ph | null | In this work we find explicitly the decoherence free subspace (DFS) for a two
two-level system in a common squeezed vacuum bath. We also find an orthogonal
basis for the DFS composed of a symmetrical and an antisymmetrical (under
particle permutation) entangled state. For any initial symmetrical state, the
master equation has one stationary state which is the symmetrical entangled
decoherence free state. In this way, one can generate entanglement via common
squeezed bath of the two systems. If the initial state does not have a definite
parity, the stationary state depends strongly on the initial conditions of the
system and it has a statistical mixture of states which belong to the DFS. We
also study the effect of the coupling between the two-level systems on the DFS.
| [
{
"version": "v1",
"created": "Wed, 8 Nov 2006 17:56:59 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Mundarain",
"D.",
""
],
[
"Orszag",
"M.",
""
]
]
|
quant-ph/0611091 | Dan Solomon | Dan Solomon | On the existence of negative energy states in QED in the temporal gauge | 9 pages | null | null | null | quant-ph | null | It is generally assumed that the vacuum state is the quantum state with the
lowest energy. However, it has been shown that this is not the case for a
Dirac-Maxwell field in the temporal gauge. In this paper we will present
another proof, different from that presented in previous work, which shows that
the vacuum state is not the minimum energy state for a Dirac-Maxwell field in
the temporal gauge.
| [
{
"version": "v1",
"created": "Wed, 8 Nov 2006 18:03:48 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Solomon",
"Dan",
""
]
]
|
quant-ph/0611092 | Monika Pogorzelska | Monika Pogorzelska and Robert Alicki | Linear dynamical entropy and free-independence for quantized maps on the
torus | 7 pages, 5 figures | null | 10.1088/1751-8113/40/13/006 | null | quant-ph | null | We study the relations between the averaged linear entropy production in
periodically measured quantum systems and ergodic properties of their classical
counterparts. Quantized linear automorphisms of the torus, both classically
chaotic and regular ones, are used as examples. Numerical calculations show
different entropy production regimes depending on the relation between the
Kolmogorov-Sinai entropy and the measurement entropy. The hypothesis of free
independence relations between the dynamics and measurement proposed to explain
the initial constant and maximal entropy production is tested numerically for
those models.
| [
{
"version": "v1",
"created": "Wed, 8 Nov 2006 18:04:18 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Pogorzelska",
"Monika",
""
],
[
"Alicki",
"Robert",
""
]
]
|
quant-ph/0611093 | Christine Muschik | Christine A. Muschik, Ines de Vega, Diego Porras, J. Ignacio Cirac | Quantum processing photonic states in optical lattices | 4 pages, 4 figures | Phys. Rev. Lett. 100, 063601 (2008) | 10.1103/PhysRevLett.100.063601 | null | quant-ph | null | The mapping of photonic states to collective excitations of atomic ensembles
is a powerful tool which finds a useful application in the realization of
quantum memories and quantum repeaters. In this work we show that cold atoms in
optical lattices can be used to perform an entangling unitary operation on the
transferred atomic excitations. After the release of the quantum atomic state,
our protocol results in a deterministic two qubit gate for photons. The
proposed scheme is feasible with current experimental techniques and robust
against the dominant sources of noise.
| [
{
"version": "v1",
"created": "Wed, 8 Nov 2006 19:31:09 GMT"
},
{
"version": "v2",
"created": "Thu, 9 Nov 2006 19:33:32 GMT"
},
{
"version": "v3",
"created": "Mon, 27 Nov 2006 15:32:38 GMT"
},
{
"version": "v4",
"created": "Wed, 31 Jan 2007 13:57:27 GMT"
}
]
| 2013-05-29T00:00:00 | [
[
"Muschik",
"Christine A.",
""
],
[
"de Vega",
"Ines",
""
],
[
"Porras",
"Diego",
""
],
[
"Cirac",
"J. Ignacio",
""
]
]
|
quant-ph/0611094 | Giacomo Mauro D'Ariano | Giacomo Mauro D'Ariano | Operational Axioms for Quantum Mechanics | New improvements have been made. Work presented at the conference
"Foundations of Probability and Physics-4, Quantum Theory: Reconsideration of
Foundations-3" held on 4-9 June at the International Centre for Mathematical
Modelling in Physics, Engineering and Cognitive Sciences, Vaxjo University,
Sweden. Also contains an errata to "How to Derive the Hilbert-Space
Formulation of Quantum Mechanics From Purely Operational Axioms",
quant-ph/0603011 | null | null | null | quant-ph | null | The mathematical formulation of Quantum Mechanics in terms of complex Hilbert
space is derived for finite dimensions, starting from a general definition of
"physical experiment" and from five simple Postulates concerning "experimental
accessibility and simplicity". For the infinite dimensional case, on the other
hand, a C*-algebra representation of physical transformations is derived,
starting from just four of the five Postulates via a Gelfand-Naimark-Segal
(GNS) construction. The present paper simplifies and sharpens the previous
derivation in version 1. The main ingredient of the axiomatization is the
postulated existence of "faithful states" that allows one to calibrate the
experimental apparatus. Such notion is at the basis of the operational
definitions of the scalar product and of the "transposed" of a physical
transformation. What is new in the present paper with respect to
quant-ph/0603011 is the operational deduction of an involution corresponding to
the "complex-conjugation" for effects, whose extension to transformations
allows to define the "adjoint" of a transformation when the extension is
composition-preserving.
| [
{
"version": "v1",
"created": "Wed, 8 Nov 2006 21:04:20 GMT"
},
{
"version": "v2",
"created": "Tue, 5 Dec 2006 02:49:14 GMT"
},
{
"version": "v3",
"created": "Fri, 8 Dec 2006 07:12:07 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"D'Ariano",
"Giacomo Mauro",
""
]
]
|
quant-ph/0611095 | Xiang-Fa Zhou | Xiang-Fa Zhou, Yong-Sheng Zhang, Guang-Can Guo | Unambiguous discrimination of mixed states: A description based on
system-ancilla coupling | 6 pages, 1 table, added some examples | Phys. Rev. A 75, 052314 (2007) | 10.1103/PhysRevA.75.052314 | null | quant-ph | null | We propose a general description on the unambiguous discrimination of mixed
states according to the system-environment coupling, and present a procedure to
reduce this to a standard semidefinite programming problem. In the two states
case, we introduce the canonical vectors and partly simplify the problem to the
case of discrimination between pairs of canonical vectors. By considering the
positivity of the two by two matrices, we obtain a series of new upper bounds
of the total success probability which depends on both the prior probabilities
and specific state structures.
| [
{
"version": "v1",
"created": "Thu, 9 Nov 2006 02:55:08 GMT"
},
{
"version": "v2",
"created": "Fri, 11 May 2007 00:58:56 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Zhou",
"Xiang-Fa",
""
],
[
"Zhang",
"Yong-Sheng",
""
],
[
"Guo",
"Guang-Can",
""
]
]
|
quant-ph/0611096 | Xiang-Fa Zhou | Xiang-Fa Zhou, Qing Lin, Yong-Sheng Zhang, Guang-Can Guo | Physical accessible transformations on a finite number of quantum states | 7 pages | null | 10.1103/PhysRevA.75.012321 | null | quant-ph | null | We consider to treat the usual probabilistic cloning, state separation,
unambiguous state discrimination, \emph{etc} in a uniform framework. All these
transformations can be regarded as special examples of generalized completely
positive trace non-increasing maps on a finite number of input states. From the
system-ancilla model we construct the corresponding unitary implementation of
pure $\to$ pure, pure $\to$ mixed, mixed $\to$ pure, and mixed $\to$ mixed
states transformations in the whole system and obtain the necessary and
sufficient conditions on the existence of the desired maps. We expect our work
will be helpful to explore what we can do on a finite set of input states.
| [
{
"version": "v1",
"created": "Thu, 9 Nov 2006 03:25:18 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Zhou",
"Xiang-Fa",
""
],
[
"Lin",
"Qing",
""
],
[
"Zhang",
"Yong-Sheng",
""
],
[
"Guo",
"Guang-Can",
""
]
]
|
quant-ph/0611097 | Mikio Kozuma | Daisuke Akamatsu, Yoshihiko Yokoi, Manabu Arikawa, Satoshi Nagatsuka,
Takahito Tanimura, Akira Furusawa and Mikio Kozuma | Ultraslow Propagation of Squeezed Vacuum Pulses with Electromagnetically
Induced Transparency | null | Physical Review Letters 99, 153602 (2007) | 10.1103/PhysRevLett.99.153602 | null | quant-ph | null | We have succeeded in observing ultraslow propagation of squeezed vacuum
pulses with electromagnetically induced transparency. Squeezed vacuum pulses
(probe lights) were incident on a laser cooled 87Rb gas together with an
intense coherent light (control light). A homodyne method sensitive to the
vacuum state was employed for detecting the probe pulse passing through the
gas. A delay of 3.1us was observed for the probe pulse having a temporal width
of 10 us.
| [
{
"version": "v1",
"created": "Thu, 9 Nov 2006 04:08:21 GMT"
},
{
"version": "v2",
"created": "Fri, 25 May 2007 14:01:04 GMT"
},
{
"version": "v3",
"created": "Thu, 16 Aug 2007 02:43:01 GMT"
},
{
"version": "v4",
"created": "Sun, 27 Jan 2008 12:08:36 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Akamatsu",
"Daisuke",
""
],
[
"Yokoi",
"Yoshihiko",
""
],
[
"Arikawa",
"Manabu",
""
],
[
"Nagatsuka",
"Satoshi",
""
],
[
"Tanimura",
"Takahito",
""
],
[
"Furusawa",
"Akira",
""
],
[
"Kozuma",
"Mikio",
""
]
]
|
quant-ph/0611098 | Menachem Tsindlekht | Mark E. Perel'man | Near field in quantum electrodynamics: Green functions, Lorentz
condition, "nonlocality in the small", frustrated total reflection | 21 pages | null | 10.1002/andp.200610240 | null | quant-ph | null | Investigation of near field of QED requires the refuse from an averaging of
the Lorentz condition that smooths out some field peculiarities. Instead of it
Schwinger decomposition of the 4-potential with the Bogoliubov method of
interaction switching in time and in space regions is considered. At such
approach near field is describable by the part of covariant Green function of
QED, the fast-damping Schwinger function formed by longitudinal and scalar
components of Aμ none restricted by light cone. This description reveals
possibility of superluminal phenomena within the near field zone as a
"nonlocality in the small". Some specification of Bogoliubov method allows, as
examples, descriptions of near fields of point-like charge and at FTIR
phenomena. Precisely such possibilities of nonlocal interactions are revealed
in the common QED expressions for the Van-der-Waals and Casimir interactions
and in the F\"{o}rster law.
Key words: Lorentz condition, near field, propagators, superluminal, FTIR.
PACS: 03.30.+p, 12.20.-m, 13.40.-f, 68.37.Uv.
| [
{
"version": "v1",
"created": "Thu, 9 Nov 2006 13:37:22 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Perel'man",
"Mark E.",
""
]
]
|
quant-ph/0611099 | Mark Oxborrow | Mark Oxborrow | Traceable 2D finite-element simulation of the whispering-gallery modes
of axisymmetric electromagnetic resonators | 10 pages, 8 figures, submitted to IEEE Microwave Theory and
Techniques. Last revision March 19 2007. This paper is a significantly
abridged/revised version of quant-ph/0607156 | null | 10.1109/TMTT.2007.897850 | null | quant-ph | null | This paper explains how a popular, commercially-available software package
for solving partial-differential-equations (PDEs), as based on the
finite-element method (FEM), can be configured to calculate, efficiently, the
frequencies and fields of the whispering-gallery (WG) modes of axisymmetric
dielectric resonators. The approach is traceable; it exploits the PDE-solver's
ability to accept the definition of solutions to Maxwell's equations in
so-called `weak form'. Associated expressions and methods for estimating a WG
mode's volume, filling factor(s) and, in the case of closed(open) resonators,
its wall(radiation) loss, are provided. As no transverse approximation is
imposed, the approach remains accurate even for quasi-transverse
magnetic/electric modes of low, finite azimuthal mode order. The approach's
generality and utility are demonstrated by modeling several non-trivial
structures: (i) two different optical microcavities [one toroidal made of
silica, the other an AlGaAs microdisk]; (ii) a 3rd-order sapphire:air Bragg
cavity; (iii) two different cryogenic sapphire WG-mode resonators; both (ii)
and (iii) operate in the microwave X-band. By fitting one of (iii) to a set of
measured resonance frequencies, the dielectric constants of sapphire at
liquid-helium temperature have been estimated.
| [
{
"version": "v1",
"created": "Thu, 9 Nov 2006 20:37:35 GMT"
},
{
"version": "v2",
"created": "Mon, 19 Mar 2007 16:53:42 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Oxborrow",
"Mark",
""
]
]
|
quant-ph/0611100 | Qing Xu | M. B. Costa e Silva, Q. Xu, S. Agnolini, P. Gallion, F. J. Mendieta | Homodyne QPSK Detection for Quantum Key Distribution | 3 pages, 4 figures, COTA/OSA Conference, Whistler, British Columbia,
Canada, June 2006 2006 | COTA/OSA Conference Proceeding 2006 | null | null | quant-ph | null | We present a QKD system with fainted pulses using self-homodyne coherent
detection in optical fibers at 1543nm. BB84 protocol key is encoded in the
optical phase using a twoelectrode Mach-Zehnder modulator, producing a QPSK
modulation.
| [
{
"version": "v1",
"created": "Thu, 9 Nov 2006 14:06:22 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Silva",
"M. B. Costa e",
""
],
[
"Xu",
"Q.",
""
],
[
"Agnolini",
"S.",
""
],
[
"Gallion",
"P.",
""
],
[
"Mendieta",
"F. J.",
""
]
]
|
quant-ph/0611101 | Astrid Lambrecht | A. Lambrecht, V.V. Nesvizhevsky, R. Onofrio, and S. Reynaud | Development of a high sensitivity torsional balance for the study of the
Casimir force in the 1-10 micrometer range | 10 pages, 2 figures | Class. Quantum Grav. 22, 5397 (2005) | 10.1088/0264-9381/22/24/012 | null | quant-ph | null | We discuss a proposal to measure the Casimir force in the parallel plate
configuration in the $1-10\mu$m range via a high-sensitivity torsional balance.
This will allow to measure the thermal contribution to the Casimir force
therefore discriminating between the various approaches discussed so far. The
accurate control of the Casimir force in this range of distances is also
required to improve the limits to the existence of non-Newtonian forces in the
micrometer range predicted by unification models of fundamental interactions.
| [
{
"version": "v1",
"created": "Thu, 9 Nov 2006 14:14:21 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Lambrecht",
"A.",
""
],
[
"Nesvizhevsky",
"V. V.",
""
],
[
"Onofrio",
"R.",
""
],
[
"Reynaud",
"S.",
""
]
]
|
quant-ph/0611102 | Qing Xu Mr. | M. B. Costa e Silva, Q. Xu, S. Agnolini, S. Guilley, J-L. Danger, P.
Gallion, F. J. Mendieta | Integrating a QPSK Quantum Key Distribution Link | 2 pages, 4 figures, European Conference on Optical Communication 2006 | ECOC 2006 Proceeding | null | null | quant-ph | null | We present the integration of the optical and electronic subsystems of a
BB84-QKD fiber link. A highspeed FPGA MODEM generates the random QPSK sequences
for a fiber-optic delayed self-homodyne scheme using APD detectors.
| [
{
"version": "v1",
"created": "Thu, 9 Nov 2006 15:04:35 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Silva",
"M. B. Costa e",
""
],
[
"Xu",
"Q.",
""
],
[
"Agnolini",
"S.",
""
],
[
"Guilley",
"S.",
""
],
[
"Danger",
"J-L.",
""
],
[
"Gallion",
"P.",
""
],
[
"Mendieta",
"F. J.",
""
]
]
|
quant-ph/0611103 | Astrid Lambrecht | A. Lambrecht, P. A. Maia Neto, and S. Reynaud | The Casimir effect within scattering theory | 15 pages, 12 figures | New Journal of Physics 8, 243 (2006) | 10.1088/1367-2630/8/10/243 | null | quant-ph | null | We review the theory of the Casimir effect using scattering techniques. After
years of theoretical efforts, this formalism is now largely mastered so that
the accuracy of theory-experiment comparisons is determined by the level of
precision and pertinence of the description of experimental conditions. Due to
an imperfect knowledge of the optical properties of real mirrors used in the
experiment, the effect of imperfect reflection remains a source of uncertainty
in theory-experiment comparisons. For the same reason, the temperature
dependence of the Casimir force between dissipative mirrors remains a matter of
debate. We also emphasize that real mirrors do not obey exactly the assumption
of specular reflection, which is used in nearly all calculations of material
and temperature corrections. This difficulty may be solved by using a more
general scattering formalism accounting for non-specular reflection with
wavevectors and field polarizations mixed. This general formalism has already
been fruitfully used for evaluating the effect of roughness on the Casimir
force as well as the lateral Casimir force appearing between corrugated
surfaces. The commonly used `proximity force approximation' turns out to lead
to inaccuracies in the description of these two effects.
| [
{
"version": "v1",
"created": "Thu, 9 Nov 2006 16:43:31 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Lambrecht",
"A.",
""
],
[
"Neto",
"P. A. Maia",
""
],
[
"Reynaud",
"S.",
""
]
]
|
quant-ph/0611104 | Claudia Eberlein | Claudia Eberlein and Robert Zietal | Force on a neutral atom near conducting microstructures | 7 pages, 5 figures | Phys. Rev. A 75, 032516 (2007) | 10.1103/PhysRevA.75.032516 | null | quant-ph | null | We derive the non-retarded energy shift of a neutral atom for two different
geometries. For an atom close to a cylindrical wire we find an integral
representation for the energy shift, give asymptotic expressions, and
interpolate numerically. For an atom close to a semi-infinite halfplane we
determine the exact Green's function of the Laplace equation and use it derive
the exact energy shift for an arbitrary position of the atom. These results can
be used to estimate the energy shift of an atom close to etched microstructures
that protrude from substrates.
| [
{
"version": "v1",
"created": "Thu, 9 Nov 2006 18:13:34 GMT"
}
]
| 2009-12-07T00:00:00 | [
[
"Eberlein",
"Claudia",
""
],
[
"Zietal",
"Robert",
""
]
]
|
quant-ph/0611105 | Daejin Shin | Daejin Shin, Ming-Chak Ho, and J. Shumway | Ab-initio path integral techniques for molecules | 9 pages, 6 figures | null | null | null | quant-ph | null | Path integral Monte Carlo with Green's function analysis allows the sampling
of quantum mechanical properties of molecules at finite temperature. While a
high-precision computation of the energy of the Born-Oppenheimer surface from
path integral Monte Carlo is quite costly, we can extract many properties
without explicitly calculating the electronic energies. We demonstrate how
physically relevant quantities, such as bond-length, vibrational spectra, and
polarizabilities of molecules may be sampled directly from the path integral
simulation using Matsubura (temperature) Green's functions (imaginary-time
correlation functions). These calculations on the hydrogen molecule are a
proof-of-concept, designed to motivate new work on fixed-node path-integral
calculations for molecules.
| [
{
"version": "v1",
"created": "Thu, 9 Nov 2006 20:14:57 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Shin",
"Daejin",
""
],
[
"Ho",
"Ming-Chak",
""
],
[
"Shumway",
"J.",
""
]
]
|
quant-ph/0611106 | Michael Nathanson | M. Nathanson, M.B. Ruskai | Pauli Diagonal Channels Constant on Axes | null | J. Phys. A: Math. Theor. 40 (2007) 8171-8204. | 10.1088/1751-8113/40/28/S22 | null | quant-ph | null | We define and study the properties of channels which are analogous to unital
qubit channels in several ways. A full treatment can be given only when the
dimension d is a prime power, in which case each of the (d+1) mutually unbiased
bases (MUB) defines an axis. Along each axis the channel looks like a
depolarizing channel, but the degree of depolarization depends on the axis.
When d is not a prime power, some of our results still hold, particularly in
the case of channels with one symmetry axis. We describe the convex structure
of this class of channels and the subclass of entanglement breaking channels.
We find new bound entangled states for d = 3.
For these channels, we show that the multiplicativity conjecture for maximal
output p-norm holds for p=2. We also find channels with behavior not exhibited
by unital qubit channels, including two pairs of orthogonal bases with equal
output entropy in the absence of symmetry. This provides new numerical evidence
for the additivity of minimal output entropy.
| [
{
"version": "v1",
"created": "Thu, 9 Nov 2006 21:12:01 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Nathanson",
"M.",
""
],
[
"Ruskai",
"M. B.",
""
]
]
|
quant-ph/0611107 | Kamil Br\'adler | K. Bradler | Optimal and covariant single-copy LOCC transformation between two
two-qubit states | 10 pages, minor corrections, accepted for publication in Physics
Letters A | null | 10.1016/j.physleta.2007.01.067 | null | quant-ph | null | Given two two-qubit pure states characterized by their Schmidt numbers we
investigate an optimal strategy to convert the states between themselves with
respect to their local unitary invariance. We discuss the efficiency of this
transformation and its connection to LOCC convertibility properties between two
single-copy quantum states. As an illustration of the investigated
transformations we present a communication protocol where in spite of all
expectations a shared maximally entangled pair between two participants is the
worst quantum resource.
| [
{
"version": "v1",
"created": "Thu, 9 Nov 2006 22:37:01 GMT"
},
{
"version": "v2",
"created": "Sat, 11 Nov 2006 19:28:03 GMT"
},
{
"version": "v3",
"created": "Tue, 23 Jan 2007 02:03:25 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Bradler",
"K.",
""
]
]
|
quant-ph/0611108 | John Morton | John J. L. Morton, Alexei M. Tyryshkin, Arzhang Ardavan, Kyriakos
Porfyrakis, S. A. Lyon and G. Andrew D. Briggs | Environmental effects on electron spin relaxation in N@C60 | 7 pages, 6 figures | null | 10.1103/PhysRevB.76.085418 | null | quant-ph | null | We examine environmental effects of surrounding nuclear spins on the electron
spin relaxation of the N@C60 molecule (which consists of a nitrogen atom at the
centre of a fullerene cage). Using dilute solutions of N@C60 in regular and
deuterated toluene, we observe and model the effect of translational diffusion
of nuclear spins of the solvent molecules on the N@C60 electron spin relaxation
times. We also study spin relaxation in frozen solutions of N@C60 in CS2, to
which small quantities of a glassing agent, S2Cl2 are added. At low
temperatures, spin relaxation is caused by spectral diffusion of surrounding
nuclear 35Cl and 37Cl spins in the S2Cl2, but nevertheless, at 20 K, T2 times
as long as 0.23 ms are observed.
| [
{
"version": "v1",
"created": "Thu, 9 Nov 2006 23:59:14 GMT"
},
{
"version": "v2",
"created": "Sun, 12 Nov 2006 21:22:42 GMT"
},
{
"version": "v3",
"created": "Sun, 15 Apr 2007 18:54:51 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Morton",
"John J. L.",
""
],
[
"Tyryshkin",
"Alexei M.",
""
],
[
"Ardavan",
"Arzhang",
""
],
[
"Porfyrakis",
"Kyriakos",
""
],
[
"Lyon",
"S. A.",
""
],
[
"Briggs",
"G. Andrew D.",
""
]
]
|
quant-ph/0611109 | Daniel Van Gent | Robert Desbrandes and Daniel Van Gent | Intercontinental quantum liaisons between entangled electrons in ion
traps of thermoluminescent crystals | null | null | null | null | quant-ph | null | The experiments reported in this paper were carried out with space-separated
entangled thermoluminescent dosimetry (TLD) crystals in Baton Rouge, Louisiana
(USA) and Givarlais (France) at 8,182 km between entangled samples. Samples
consisted of doped lithium fluoride TLD's that were simultaneously irradiated
in pairs together at one location by Bremsstrahlung radiation generated by a
Varian CLINAC unit. One of the paired TLD crystals was then mailed to Baton
Rouge and its entangled counterpart remained in Givarlais. The crystal in Baton
Rouge (master) was then subjected to thermal stimulation which elicited a
measurable light emission response in the counterpart (slave) under a
photomultiplier in Givarlais. Highly correlated passive light emissions were
observed in the nonheated slave TLD while the master TLD was ramped up in
temperature and then allowed to cool to ambient temperature. Maximum
correlations in the slave TLD light emissions were observed at the turn around
temperature which is the point where the master TLD temperature is allowed to
decrease. The experimenter in Girvalais was thus able to determine with high
accuracy the point in time at which the master TLD heating oven was turned off
(turn around point) without any communication between the experimenters during
the heating-cooling phase of the experiment. The implications of these observed
results are of great significance for quantum communication technology.
| [
{
"version": "v1",
"created": "Fri, 10 Nov 2006 01:19:34 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Desbrandes",
"Robert",
""
],
[
"Van Gent",
"Daniel",
""
]
]
|
quant-ph/0611110 | Howard N. Barnum | Howard Barnum | Coordinating quantum agents' perspectives: convex operational theories,
quantum information, and quantum foundations | 41 pages. Greatly extended version of quant-ph/0304159 with several
additional topics discussed--more philosophical material toward the
beginning, more technical (but still fairly discursive) material toward the
end | null | null | null | quant-ph | null | In this paper, I propose a project of enlisting quantum information science
as a source of task-oriented axioms for use in the investigation of operational
theories in a general framework capable of encompassing quantum mechanics,
classical theory, and more. Whatever else they may be, quantum states of
systems are compendia of probabilities for the outcomes of possible operations
we may perform on the systems: ``operational theories.'' I discuss appropriate
general frameworks for such theories, in which convexity plays a key role. Such
frameworks are appropriate for investigating what things look like from an
``inside view,'' i.e. for describing perspectival information that one
subsystem of the world can have about another. Understanding how such views can
combine, and whether an overall ``geometric'' picture (``outside view'')
coordinating them all can be had, even if this picture is very different in
nature from the structure of the perspectives within it, is the key to
understanding whether we may be able to achieve a unified, ``objective''
physical view in which quantum mechanics is the appropriate description for
certain perspectives, or whether quantum mechanics is truly telling us we must
go beyond this ``geometric'' conception of physics. The nature of information,
its flow and processing, as seen from various operational persepectives, is
likely to be key to understanding whether and how such coordination and
unification can be achieved.
| [
{
"version": "v1",
"created": "Fri, 10 Nov 2006 00:50:56 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Barnum",
"Howard",
""
]
]
|
quant-ph/0611111 | Francesco Buscemi Dr | Francesco Buscemi | Channel correction via quantum erasure | 4 pages RevTex4. Revised version, drastically modified. To appear on
PRL | Phys. Rev. Lett. 99, 180501 (2007) | 10.1103/PhysRevLett.99.180501 | null | quant-ph | null | By exploiting a generalization of recent results on environment-assisted
channel correction, we show that, whenever a quantum system undergoes a channel
realized as an interaction with a probe, the more efficiently the information
about the input state can be erased from the probe, the higher is the
corresponding entanglement fidelity of the corrected channel, and vice-versa.
The present analysis applies also to channels for which perfect quantum erasure
is impossible, thus extending the original quantum eraser arrangement, and
naturally embodies a general information-disturbance tradeoff.
| [
{
"version": "v1",
"created": "Fri, 10 Nov 2006 01:23:48 GMT"
},
{
"version": "v2",
"created": "Mon, 10 Sep 2007 06:04:47 GMT"
}
]
| 2007-10-29T00:00:00 | [
[
"Buscemi",
"Francesco",
""
]
]
|
quant-ph/0611112 | Alexandre Soujaeff | Alexandre Soujaeff (JST-CREST, RIES, Hokkaido University), Shigeki
Takeuchi (RIES, Hokkaido University), Keiji Sasaki (RIES, Hokkaido
University), Toshio Hasegawa (Mitsubishi Electric Corporation), Mitsuru
Matsui (Mitsubishi Electric Corporation) | Heralded single photon source at 1550 nm from pulsed parametric down
conversion | 8 pages, 1 figure, accepted by Journal of Modern Optics | null | 10.1080/09500340600742239 | null | quant-ph | null | Heralding of single photon at 1550 nm from pump pulsed non degenerate
spontaneous parametric downconversion is demonstrated. P(1) and P(2) of our
source are 0.1871 and 2.4 x 10 ^-3 respectively. Triggering of our source is
2.16 x 10^5 trigger.s^-1. This source may be used in QKD system.
| [
{
"version": "v1",
"created": "Fri, 10 Nov 2006 08:16:33 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Soujaeff",
"Alexandre",
"",
"JST-CREST, RIES, Hokkaido University"
],
[
"Takeuchi",
"Shigeki",
"",
"RIES, Hokkaido University"
],
[
"Sasaki",
"Keiji",
"",
"RIES, Hokkaido\n University"
],
[
"Hasegawa",
"Toshio",
"",
"Mitsubishi Electric Corporation"
],
[
"Matsui",
"Mitsuru",
"",
"Mitsubishi Electric Corporation"
]
]
|
quant-ph/0611113 | Stefano Longhi | Stefano Longhi | Non-Markovian Decay and Lasing Condition in an Optical Microcavity
Coupled to a Structured Reservoir | to appear in Phys. Rev. A (December 2006 issue) | Phys. Rev. A 74, 063826 (2006) | 10.1103/PhysRevA.74.063826 | null | quant-ph | null | The decay dynamics of the classical electromagnetic field in a leaky optical
resonator supporting a single mode coupled to a structured continuum of modes
(reservoir) is theoretically investigated, and the issue of threshold condition
for lasing in presence of an inverted medium is comprehensively addressed.
Specific analytical results are given for a single-mode microcavity resonantly
coupled to a coupled resonator optical waveguide (CROW), which supports a band
of continuous modes acting as decay channels. For weak coupling, the usual
exponential Weisskopf-Wigner (Markovian) decay of the field in the bare
resonator is found, and the threshold for lasing increases linearly with the
coupling strength. As the coupling between the microcavity and the structured
reservoir increases, the field decay in the passive cavity shows non
exponential features, and correspondingly the threshold for lasing ceases to
increase, reaching a maximum and then starting to decrease as the coupling
strength is further increased. A singular behavior for the "laser phase
transition", which is a clear signature of strong non-Markovian dynamics, is
found at critical values of the coupling between the microcavity and the
reservoir.
| [
{
"version": "v1",
"created": "Fri, 10 Nov 2006 08:59:02 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Longhi",
"Stefano",
""
]
]
|
quant-ph/0611114 | Vladimir Manko | Sergio De Nicola Renato Fedele, Margarita A. Man'ko and Vladimir I.
Man'ko | New Inequalities for Tomograms in the Probability Representation of
Quantum States | 10 pages,presented at International Workshop "Nonlinear Physics.Thery
and Experiment.IV" (Gallipoli,Lecce,Italy,2006) to be published in Special
Issue of "Theoretical and Mathematical Physics" | null | null | null | quant-ph | null | New inequalities for symplectic tomograms of quantum states and their
connection with entropic uncertainty relations are discussed within the
framework of the probability representation of quantum mechanics.
| [
{
"version": "v1",
"created": "Fri, 10 Nov 2006 09:35:43 GMT"
}
]
| 2016-08-16T00:00:00 | [
[
"Fedele",
"Sergio De Nicola Renato",
""
],
[
"Man'ko",
"Margarita A.",
""
],
[
"Man'ko",
"Vladimir I.",
""
]
]
|
quant-ph/0611115 | Pankaj Agrawal | Arun K. Pati and Pankaj Agrawal | Probabilistic Teleportation of a Qudit | Latex, no figures | null | 10.1016/j.physleta.2007.07.016 | IP/BBSR/2006-17 | quant-ph | null | It is known that if the shared resource is a maximally entangled state then
it is possible to teleport an unknown state with unit fidelity and unit
probability. However, if the shared resource is a non-maximally entangled state
then one has to follow a probabilistic scheme where one can teleport a qubit
with unit fidelity and non-unit probability. In this work, we investigate the
feasibility of using partially entangled states as a resource for quantum
teleportation of a qudit. We also give an expression for the probability of
successful teleportation of an unknown qudit.
| [
{
"version": "v1",
"created": "Fri, 10 Nov 2006 12:08:05 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Pati",
"Arun K.",
""
],
[
"Agrawal",
"Pankaj",
""
]
]
|
quant-ph/0611116 | H. J. Korsch | B. Bahr and H. J. Korsch | Quantum mechanics on a circle: Husimi phase space distributions and
semiclassical coherent state propagators | 29 pages | J.Phys.A40:3959-3985,2007 | 10.1088/1751-8113/40/14/013 | null | quant-ph | null | We discuss some basic tools for an analysis of one-dimensionalquantum systems
defined on a cyclic coordinate space. The basic features of the generalized
coherent states, the complexifier coherent states are reviewed. These states
are then used to define the corresponding (quasi)densities in phase space. The
properties of these generalized Husimi distributions are discussed, in
particular their zeros.Furthermore, the use of the complexifier coherent states
for a semiclassical analysis is demonstrated by deriving a semiclassical
coherent state propagator in phase space.
| [
{
"version": "v1",
"created": "Fri, 10 Nov 2006 15:11:27 GMT"
},
{
"version": "v2",
"created": "Wed, 10 Jan 2007 17:07:07 GMT"
}
]
| 2008-11-26T00:00:00 | [
[
"Bahr",
"B.",
""
],
[
"Korsch",
"H. J.",
""
]
]
|
quant-ph/0611117 | Anastasia Rodichkina | A.M. Basharov, V.N. Gorbachev, A.A. Rodichkina | Decay and storage of multiparticle entangled states of atoms in
collective thermostat | null | Phys.Rev.A 74, 042313 (2006) | 10.1103/PhysRevA.74.042313 | null | quant-ph | null | We derive a master equation describing the collective decay of two-level
atoms inside a single mode cavity in the dispersive limit. By considering
atomic decay in the collective thermostat, we found a decoherence-free subspace
of the multiparticle entangled states of the W-like class. We present a scheme
for writing and storing these states in collective thermostat.
| [
{
"version": "v1",
"created": "Fri, 10 Nov 2006 15:44:29 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Basharov",
"A. M.",
""
],
[
"Gorbachev",
"V. N.",
""
],
[
"Rodichkina",
"A. A.",
""
]
]
|
quant-ph/0611118 | Roberto Onofrio | M Brown-Hayes, J.H. Brownell, D.A.R. Dalvit, W.J. Kim, A. Lambrecht,
F.C. Lombardo, F.D. Mazzitelli, S.M. Middleman, V.V. Nesvizhevsky, R.
Onofrio, and S. Reynaud | Thermal and dissipative effects in Casimir physics | Contribution to QFEXT'06, appeared in special issue of Journal of
Physics A | J. Phys. A 39, 6195 (2006) | 10.1088/0305-4470/39/21/S10 | null | quant-ph | null | We report on current efforts to detect the thermal and dissipative
contributions to the Casimir force. For the thermal component, two experiments
are in progress at Dartmouth and at the Institute Laue Langevin in Grenoble.
The first experiment will seek to detect the Casimir force at the largest
explorable distance using a cylinder-plane geometry which offers various
advantages with respect to both sphere-plane and parallel-plane geometries. In
the second experiment, the Casimir force in the parallel-plane configuration is
measured with a dedicated torsional balance, up to 10 micrometers. Parallelism
of large surfaces, critical in this configuration, is maintained through the
use of inclinometer technology already implemented at Grenoble for the study of
gravitationally bound states of ultracold neutrons, For the dissipative
component of the Casimir force, we discuss detection techniques based upon the
use of hyperfine spectroscopy of ultracold atoms and Rydberg atoms. Although
quite challenging, this triad of experimental efforts, if successful, will give
us a better knowledge of the interplay between quantum and thermal fluctuations
of the electromagnetic field and of the nature of dissipation induced by the
motion of objects in a quantum vacuum.
| [
{
"version": "v1",
"created": "Fri, 10 Nov 2006 16:10:05 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Brown-Hayes",
"M",
""
],
[
"Brownell",
"J. H.",
""
],
[
"Dalvit",
"D. A. R.",
""
],
[
"Kim",
"W. J.",
""
],
[
"Lambrecht",
"A.",
""
],
[
"Lombardo",
"F. C.",
""
],
[
"Mazzitelli",
"F. D.",
""
],
[
"Middleman",
"S. M.",
""
],
[
"Nesvizhevsky",
"V. V.",
""
],
[
"Onofrio",
"R.",
""
],
[
"Reynaud",
"S.",
""
]
]
|
quant-ph/0611119 | Paola Zizzi | Paola Zizzi | Basic Logic and Quantum Entanglement | 10 pages, 1 figure,LaTeX. Shorter version for proceedings
requirements. Contributed paper at DICE2006, Piombino, Italy | J.Phys.Conf.Ser.67:012045,2007 | 10.1088/1742-6596/67/1/012045 | null | quant-ph hep-th math.LO | null | As it is well known, quantum entanglement is one of the most important
features of quantum computing, as it leads to massive quantum parallelism,
hence to exponential computational speed-up. In a sense, quantum entanglement
is considered as an implicit property of quantum computation itself. But...can
it be made explicit? In other words, is it possible to find the connective
"entanglement" in a logical sequent calculus for the machine language? And
also, is it possible to "teach" the quantum computer to "mimic" the EPR
"paradox"? The answer is in the affirmative, if the logical sequent calculus is
that of the weakest possible logic, namely Basic logic. A weak logic has few
structural rules. But in logic, a weak structure leaves more room for
connectives (for example the connective "entanglement"). Furthermore, the
absence in Basic logic of the two structural rules of contraction and weakening
corresponds to the validity of the no-cloning and no-erase theorems,
respectively, in quantum computing.
| [
{
"version": "v1",
"created": "Fri, 10 Nov 2006 16:17:18 GMT"
},
{
"version": "v2",
"created": "Mon, 5 Feb 2007 14:06:15 GMT"
}
]
| 2008-11-26T00:00:00 | [
[
"Zizzi",
"Paola",
""
]
]
|
quant-ph/0611120 | Bing Qi | Lei-Lei Huang, Bing Qi, Li Qian, Hoi-Kwong Lo | Continuous-Variables Quantum Key Distribution over Standard Telecom
Fiber | This paper has been withdrawn | null | null | null | quant-ph | null | This paper has been withdrawn
| [
{
"version": "v1",
"created": "Fri, 10 Nov 2006 16:37:52 GMT"
},
{
"version": "v2",
"created": "Thu, 3 May 2007 14:50:48 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Huang",
"Lei-Lei",
""
],
[
"Qi",
"Bing",
""
],
[
"Qian",
"Li",
""
],
[
"Lo",
"Hoi-Kwong",
""
]
]
|
quant-ph/0611121 | Jan Ivar Korsbakken | Jan Ivar Korsbakken, K. Birgitta Whaley, Jonathan DuBois, J. Ignacio
Cirac | A measurement-based measure of the size of macroscopic quantum
superpositions | 21 pages, 20 figures. Accepted by Phys. Rev. A. Replaced old version
with accepted version. Significant changes and improvements, particularly to
section on 1-particle measurements | Phys. Rev. A 75, 042106 (2007) | 10.1103/PhysRevA.75.042106 | null | quant-ph | null | Recent experiments claiming formation of quantum superposition states in near
macroscopic sys- tems raise the question of how the sizes of general quantum
superposition states in an interacting system are to be quantified. We propose
here a measure of size for such superposition states that is based on what
measurements can be performed to probe and distinguish the different branches
of the state. The measure allows comparison of the effective size for
superposition states in very different physical systems. It can be applied to a
very general class of superposition states and reproduces known results for
near-ideal cases. Comparison with a prior measure based on analy- sis of
coherence between branches indicates that significantly smaller effective
superposition sizes result from our measurement-based measure. Application to a
system of interacting bosons in a double-well trapping potential shows that the
effective superposition size is strongly dependent on the relative magnitude of
the barrier height and interparticle interaction.
| [
{
"version": "v1",
"created": "Sat, 11 Nov 2006 22:56:52 GMT"
},
{
"version": "v2",
"created": "Tue, 10 Apr 2007 01:37:24 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Korsbakken",
"Jan Ivar",
""
],
[
"Whaley",
"K. Birgitta",
""
],
[
"DuBois",
"Jonathan",
""
],
[
"Cirac",
"J. Ignacio",
""
]
]
|
quant-ph/0611122 | Zhang Chi | Chi Zhang, Guoming Wang, Mingsheng Ying | Discrimination between pure states and mixed states | null | null | 10.1103/PhysRevA.75.062306 | null | quant-ph | null | In this paper, we discuss the problem of determining whether a quantum system
is in a pure state, or in a mixed state. We apply two strategies to settle this
problem: the unambiguous discrimination and the maximum confidence
discrimination. We also proved that the optimal versions of both strategies are
equivalent. The efficiency of the discrimination is also analyzed. This scheme
also provides a method to estimate purity of quantum states, and Schmidt
numbers of composed systems.
| [
{
"version": "v1",
"created": "Sat, 11 Nov 2006 07:01:31 GMT"
},
{
"version": "v2",
"created": "Fri, 9 Feb 2007 14:11:19 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Zhang",
"Chi",
""
],
[
"Wang",
"Guoming",
""
],
[
"Ying",
"Mingsheng",
""
]
]
|
quant-ph/0611123 | Qing Xu Mr. | Q. XU, M.B. Costa e Silva, S. Agnolini, P. Gallion, F.J. Mendieta | Photon Counting and Super Homodyne Detection of Weak QPSK Signals for
Quantum Key Distribution | 2 pages, 3 figues, EOS Annual Meeting 2006, Topical Meeting on
Extreme Optics (QEOD/EPS), Paris, Oct. 2006 | EOS 2006 Annual meeting Proceeding | null | null | quant-ph | null | We compare the principles and experimental results of two different QPSK
signal detection configurations, photon counting and super homodyning, for
applications in fiber-optic Quantum Key Distribution (QKD) systems operating at
telecom wavelength, using the BB84 protocol.
| [
{
"version": "v1",
"created": "Sat, 11 Nov 2006 12:21:04 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"XU",
"Q.",
""
],
[
"Silva",
"M. B. Costa e",
""
],
[
"Agnolini",
"S.",
""
],
[
"Gallion",
"P.",
""
],
[
"Mendieta",
"F. J.",
""
]
]
|
quant-ph/0611124 | Hossein Movahhedian | Hossein Movahhedian | Stronger Violation of Local Theories with Equalities | 8 pages, RevTeX4 | J. Phys. A: Math. Theor. 40 (2007) 2839-2847 | 10.1088/1751-8113/40/11/018 | null | quant-ph | null | Bell type inequalities are used to test local realism against quantum
theory.In this paper, we consider a two party system with two settings and two
possible outcomes on each side, and derive equalities in local theories which
are violated by quantum theory by a factor of 1.522 tolerating 0.586 fraction
of white noise admixture which is twice that of the previous results.
| [
{
"version": "v1",
"created": "Sat, 11 Nov 2006 13:58:47 GMT"
},
{
"version": "v2",
"created": "Fri, 1 Dec 2006 14:24:28 GMT"
},
{
"version": "v3",
"created": "Sun, 4 Feb 2007 08:35:05 GMT"
},
{
"version": "v4",
"created": "Fri, 16 Feb 2007 01:14:45 GMT"
},
{
"version": "v5",
"created": "Thu, 1 Mar 2007 03:16:30 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Movahhedian",
"Hossein",
""
]
]
|
quant-ph/0611125 | Subhashish Banerjee | Subhashish Banerjee and R. Ghosh | Structure of propagators for quantum nondemolition systems | 7 page, no figures, REVTeX4 | null | null | null | quant-ph | null | In the scheme of a quantum nondemolition (QND) measurement, an observable is
measured without perturbing its evolution. In the context of studies of
decoherence in quantum computing, we examine the `open' quantum system of a
two-level atom, or equivalently, a spin-1/2 system, in interaction with quantum
reservoirs of either oscillators or spins, under the QND condition of the
Hamiltonian of the system commuting with the system-reservoir interaction. The
propagators for these QND Hamiltonians are shown to be connected to the
squeezing and rotation operators for the two baths, respectively. Squeezing and
rotation being both phase space area-preserving canonical transformations, this
brings out an interesting analogy between the energy-preserving QND
Hamiltonians and the homogeneous linear canonical transformations.
| [
{
"version": "v1",
"created": "Sat, 11 Nov 2006 14:33:50 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Banerjee",
"Subhashish",
""
],
[
"Ghosh",
"R.",
""
]
]
|
quant-ph/0611126 | Zeqian Chen | Zeqian Chen | Variants of Bell inequalities | 8 pages | null | null | null | quant-ph | null | A family of Bell-type inequalities is present, which are constructed directly
from the "standard" Bell inequalities involving two dichotomic observables per
site. It is shown that the inequalities are violated by all the generalized
Greenberger-Horne-Zeilinger states of multiqubits. Remarkably, our new
inequalities can provide stronger non-locality tests in a sense that the local
reality inequalities are exponentially stronger than the corresponding
multipartite separability inequalities. This reveals that the exponential
violation of local realism by separable states is an interesting consequence of
quantum fluctuation of multipartite systems.
| [
{
"version": "v1",
"created": "Mon, 13 Nov 2006 11:37:00 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Chen",
"Zeqian",
""
]
]
|
quant-ph/0611127 | Subhashish Banerjee | Subhashish Banerjee and R. Ghosh | Functional integral treatment of some quantum nondemolition systems | 16 pages, no figures | J. Phys. A: Math. Theo. 40, 1273 (2007) | 10.1088/1751-8113/40/6/006 | RRI-TP-1106a | quant-ph | null | In the scheme of a quantum nondemolition (QND) measurement, an observable is
measured without perturbing its evolution. In the context of studies of
decoherence in quantum computing, we examine the `open' quantum system of a
two-level atom, or equivalently, a spin-1/2 system, in interaction with quantum
reservoirs of either oscillators or spins, under the QND condition of the
Hamiltonian of the system commuting with the system-reservoir interaction. For
completeness, we also examine the well-known non-QND spin-Bose problem. For all
these many-body systems, we use the methods of functional integration to work
out the propagators. The propagators for the QND Hamiltonians are shown to be
analogous to the squeezing and rotation operators, respectively, for the two
kinds of baths considered. Squeezing and rotation being both phase space
area-preserving canonical transformations, this brings out an interesting
connection between the energy-preserving QND Hamiltonians and the homogeneous
linear canonical transformations.
| [
{
"version": "v1",
"created": "Sat, 11 Nov 2006 14:50:01 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Banerjee",
"Subhashish",
""
],
[
"Ghosh",
"R.",
""
]
]
|
quant-ph/0611128 | Alex Kuzmich | S.-Y. Lan, S. D. Jenkins, T. Chaneliere, D. N. Matsukevich, C. J.
Campbell, R. Zhao, T. A. B. Kennedy, and A. Kuzmich | Dual species matter qubit entangled with light | 5 pages, 3 figures | Physical Review Letters 98, 123602 (2007) | 10.1103/PhysRevLett.98.123602 | null | quant-ph | null | We propose and demonstrate an atomic qubit based on a cold
$^{85}$Rb-$^{87}$Rb isotopic mixture, entangled with a frequency-encoded
optical qubit. The interface of an atomic qubit with a single spatial light
mode, and the ability to independently address the two atomic qubit states,
should provide the basic element of an interferometrically robust quantum
network.
| [
{
"version": "v1",
"created": "Sat, 11 Nov 2006 18:44:39 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Lan",
"S. -Y.",
""
],
[
"Jenkins",
"S. D.",
""
],
[
"Chaneliere",
"T.",
""
],
[
"Matsukevich",
"D. N.",
""
],
[
"Campbell",
"C. J.",
""
],
[
"Zhao",
"R.",
""
],
[
"Kennedy",
"T. A. B.",
""
],
[
"Kuzmich",
"A.",
""
]
]
|
quant-ph/0611129 | Kia Manouchehri | K. Manouchehri and J.B. Wang | Continuous-Time Quantum Random Walks Require Discrete Space | 19 pages, 9 figures, to appear in J. Phys. A | null | 10.1088/1751-8113/40/45/016 | null | quant-ph | null | Quantum random walks are shown to have non-intuitive dynamics which makes
them an attractive area of study for devising quantum algorithms for
long-standing open problems as well as those arising in the field of quantum
computing. In the case of continuous-time quantum random walks, such peculiar
dynamics can arise from simple evolution operators closely resembling the
quantum free-wave propagator. We investigate the divergence of quantum walk
dynamics from the free-wave evolution and show that in order for
continuous-time quantum walks to display their characteristic propagation, the
state space must be discrete. This behavior rules out many continuous quantum
systems as possible candidates for implementing continuous-time quantum random
walks.
| [
{
"version": "v1",
"created": "Sun, 12 Nov 2006 01:17:08 GMT"
},
{
"version": "v2",
"created": "Tue, 25 Sep 2007 09:33:07 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Manouchehri",
"K.",
""
],
[
"Wang",
"J. B.",
""
]
]
|
quant-ph/0611130 | Vahid Karimipour | V. Karimipour, L. Memarzadeh | Entanglement and optimal strings of qubits for memory channels | 14 pages, 8 figures, latex, accepted for publication in Physical
Review A | Phys. Rev. A 74, 062311 (2006) | 10.1103/PhysRevA.74.062311 | null | quant-ph | null | We investigate the problem of enhancement of mutual information by encoding
classical data into entangled input states of arbitrary length and show that
while there is a threshold memory or correlation parameter beyond which
entangled states outperform the separable states, resulting in a higher mutual
information, this memory threshold increases toward unity as the length of the
string increases. These observations imply that encoding classical data into
entangled states may not enhance the classical capacity of quantum channels.
| [
{
"version": "v1",
"created": "Sun, 12 Nov 2006 04:32:59 GMT"
},
{
"version": "v2",
"created": "Thu, 23 Nov 2006 04:18:05 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Karimipour",
"V.",
""
],
[
"Memarzadeh",
"L.",
""
]
]
|
quant-ph/0611131 | Klaus Wirthm\"uller | Klaus Wirthm\"uller | Homological invariants of stabilizer states | 18 pages, 4 figures | Quantum Inf. Comput. 8, 595 (2008) | null | null | quant-ph | null | We propose a new kind of invariant of multi-party stabilizer states with
respect to local Clifford equivalence. These homological invariants are
discrete entities defined in terms of the entanglement a state enjoys with
respect to arbitrary groupings of the parties, and they may be thought of as
reflecting entanglement in a qualitative way. We investigate basic properties
of the invariants and link them with known results on the extraction of GHZ
states.
| [
{
"version": "v1",
"created": "Sun, 12 Nov 2006 14:34:44 GMT"
}
]
| 2008-03-18T00:00:00 | [
[
"Wirthmüller",
"Klaus",
""
]
]
|
quant-ph/0611132 | Karl Gerd Vollbrecht | K. G. H. Vollbrecht and J. I. Cirac | Delocalized Entanglement of Atoms in optical Lattices | null | Phys. Rev. Lett. 98, 190502 (2007) | 10.1103/PhysRevLett.98.190502 | null | quant-ph cond-mat.other | null | We show how to detect and quantify entanglement of atoms in optical lattices
in terms of correlations functions of the momentum distribution. These
distributions can be measured directly in the experiments. We introduce two
kinds of entanglement measures related to the position and the spin of the
atoms.
| [
{
"version": "v1",
"created": "Sun, 12 Nov 2006 18:21:45 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Vollbrecht",
"K. G. H.",
""
],
[
"Cirac",
"J. I.",
""
]
]
|
quant-ph/0611133 | Philippe Raynal | Philippe Raynal | Unambiguous State Discrimination of two density matrices in Quantum
Information Theory | PhD thesis - August 2006 - 135 pages | null | null | null | quant-ph | null | In this thesis we study the problem of unambiguously discriminating two mixed
quantum states. We first present reduction theorems for optimal unambiguous
discrimination of two generic density matrices. We show that this problem can
be reduced to that of two density matrices that have the same rank $r$ in a
2$r$-dimensional Hilbert space. These reduction theorems also allow us to
reduce USD problems to simpler ones for which the solution might be known. As
an application, we consider the unambiguous comparison of $n$ linearly
independent pure states with a simple symmetry. Moreover, lower bounds on the
optimal failure probability have been derived. For two mixed states they are
given in terms of the fidelity. Here we give tighter bounds as well as
necessary and sufficient conditions for two mixed states to reach these bounds.
We also construct the corresponding optimal measurement. With this result, we
provide analytical solutions for unambiguously discriminating a class of
generic mixed states. This goes beyond known results which are all reducible to
some pure state case. We however show that examples exist where the bounds
cannot be reached. Next, we derive properties on the rank and the spectrum of
an optimal USD measurement. This finally leads to a second class of exact
solutions. Indeed we present the optimal failure probability as well as the
optimal measurement for unambiguously discriminating any pair of geometrically
uniform mixed states in four dimensions. This class of problems includes for
example the discrimination of both the basis and the bit value mixed states in
the BB84 QKD protocol with coherent states.
| [
{
"version": "v1",
"created": "Sun, 12 Nov 2006 20:37:40 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Raynal",
"Philippe",
""
]
]
|
quant-ph/0611134 | Yonghua Lu | N. Garcia | The One Dimensional Approachissimo Quantum Harmonic Oscillator: The
Hilbert-Polya Hamiltonian for the Primes and the Zeros of the Riemann
Function | 19 pages, 3 figures | null | null | null | quant-ph math-ph math.MP math.NT | null | I have made an ample study of one dimensional quantum oscillators, ranging
from logarithmic to exponential potentials. I have found that the eigenvalues
of the hamiltonian of the oscillator with the limiting (approachissimo)
harmonic potential (~ p(x)2) maps the zeros of the Riemann function height up
in the Riemann line. This is the potential created by the field of J(x) that is
the Riemann generator of the prime number counting function, p(x), that in turn
can be defined by an integral transformation of the Riemann zeta function. This
plays the role of the spring strength of the quantum limiting harmonic
oscillator. The number theory meaning of this result is that the roots height
up of the zeta function are the eigenvalues of a Hamiltonian whose potential is
the number of primes squared up to a given x. Therefore this may prove the
never published Hilbert-Polya conjecture. The conjecture is true but does not
imply the truth of the Riemann hypothesis. We can have complex conjugated zeros
off the Riemman line and map them with another hermitic operator and a general
expression is given for that. The zeros off the line affect the fluctuation of
the eigenvalues but not their mean values.
| [
{
"version": "v1",
"created": "Mon, 13 Nov 2006 09:48:29 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Garcia",
"N.",
""
]
]
|
quant-ph/0611135 | Jan Naudts | Tobias Verhulst and Jan Naudts | Entanglement of a microcanonical ensemble | 10 pages | J. Phys. A 40, 2475-2483 (2007) | 10.1088/1751-8113/40/10/016 | null | quant-ph | null | We replace time-averaged entanglement by ensemble-averaged entanglement and
derive a simple expression for the latter. We show how to calculate the
ensemble average for a two-spin system and for the Jaynes-Cummings model. In
both cases the time-dependent entanglement is known as well so that one can
verify that the time average coincides with the ensemble average.
| [
{
"version": "v1",
"created": "Mon, 13 Nov 2006 13:35:51 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Verhulst",
"Tobias",
""
],
[
"Naudts",
"Jan",
""
]
]
|
quant-ph/0611136 | Lucia Rizzuto | R. Passante, F. Persico, L. Rizzuto | Nonlocal field correlations and dynamical Casimir-Polder forces between
one excited- and two ground-state atoms | 17 pages, 1 figure, sub. to Phys. Rev. A | null | 10.1088/0953-4075/40/10/020 | null | quant-ph | null | The problem of nonlocality in the dynamical three-body Casimir-Polder
interaction between an initially excited and two ground-state atoms is
considered. It is shown that the nonlocal spatial correlations of the field
emitted by the excited atom during the initial part of its spontaneous decay
may become manifest in the three-body interaction. The observability of this
new phenomenon is discussed.
| [
{
"version": "v1",
"created": "Mon, 13 Nov 2006 14:51:19 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Passante",
"R.",
""
],
[
"Persico",
"F.",
""
],
[
"Rizzuto",
"L.",
""
]
]
|
quant-ph/0611137 | Julio Gea-Banacloche | Julio Gea-Banacloche and Masanao Ozawa | Minimum-energy pulses for quantum logic cannot be shared | To appear in Phys. Rev. A, Rapid Communications | null | 10.1103/PhysRevA.74.060301 | null | quant-ph | null | We show that if an electromagnetic energy pulse with average photon number
<n> is used to carry out the same quantum logical operation on a set of N
atoms, either simultaneously or sequentially, the overall error probability in
the worst case scenario (i.e., maximized over all the possible initial atomic
states) scales as N^2/<n>. This means that in order to keep the error
probability bounded by N\epsilon, with \epsilon ~ 1/<n>, one needs to use
N/\epsilon photons, or equivalently N separate "minimum-energy'' pulses: in
this sense the pulses cannot, in general, be shared. The origin for this
phenomenon is found in atom-field entanglement. These results may have
important consequences for quantum logic and, in particular, for large-scale
quantum computation.
| [
{
"version": "v1",
"created": "Mon, 13 Nov 2006 15:25:46 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Gea-Banacloche",
"Julio",
""
],
[
"Ozawa",
"Masanao",
""
]
]
|
quant-ph/0611138 | Jose Geraldo Peixoto de Faria | R. Rossi Jr., M. C. Nemes, J. G. Peixoto de Faria | Atomic detection in microwave cavity experiments: a dynamical model | 12 pages, 1 figure | null | 10.1103/PhysRevA.75.063819 | null | quant-ph | null | We construct a model for the detection of one atom maser in the context of
cavity Quantum Electrodynamics (QED) used to study coherence properties of
superpositions of electromagnetic modes. Analytic expressions for the atomic
ionization are obtained, considering the imperfections of the measurement
process due to the probabilistic nature of the interactions between the
ionization field and the atoms. Limited efficiency and false counting rates are
considered in a dynamical context, and consequent results on the information
about the state of the cavity modes are obtained.
| [
{
"version": "v1",
"created": "Mon, 13 Nov 2006 16:14:03 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Rossi",
"R.",
"Jr."
],
[
"Nemes",
"M. C.",
""
],
[
"de Faria",
"J. G. Peixoto",
""
]
]
|
quant-ph/0611139 | Paul Benioff | Paul Benioff | Fields of quantum reference frames based on different representations of
rational numbers as states of qubit strings | 24 pages, 5 figures; submitted to proceedings, 3rd Feynman Festival,
University of Maryland, 2006 | Journal of Physics: Conference Series 70 (2007) 012003 | 10.1088/1742-6596/70/1/012003 | null | quant-ph | null | In this paper fields of quantum reference frames based on gauge
transformations of rational string states are described in a way that,
hopefully, makes them more understandable than their description in an earlier
paper. The approach taken here is based on three main points: (1) There are a
large number of different quantum theory representations of natural numbers,
integers, and rational numbers as states of qubit strings. (2) For each
representation, Cauchy sequences of rational string states give a
representation of the real (and complex) numbers. A reference frame is
associated to each representation. (3) Each frame contains a representation of
all mathematical and physical theories that have the representations of the
real and complex numbers as a scalar base for the theories. These points and
other aspects of the resulting fields are then discussed and justified in some
detail. Also two different methods of relating the frame field to physics are
discussed.
| [
{
"version": "v1",
"created": "Mon, 13 Nov 2006 21:06:59 GMT"
}
]
| 2011-11-09T00:00:00 | [
[
"Benioff",
"Paul",
""
]
]
|
quant-ph/0611140 | Jens Eisert | K. Kieling, T. Rudolph, J. Eisert | Percolation, renormalization, and quantum computing with
non-deterministic gates | 5 pages, 4 figures, discussion of strategies to deal with further
imperfections extended, references updated | Phys. Rev. Lett. 99, 130501 (2007) | 10.1103/PhysRevLett.99.130501 | null | quant-ph cond-mat.stat-mech | null | We apply a notion of static renormalization to the preparation of entangled
states for quantum computing, exploiting ideas from percolation theory. Such a
strategy yields a novel way to cope with the randomness of non-deterministic
quantum gates. This is most relevant in the context of optical architectures,
where probabilistic gates are common, and cold atoms in optical lattices, where
hole defects occur. We demonstrate how to efficiently construct cluster states
without the need for rerouting, thereby avoiding a massive amount of
conditional dynamics; we furthermore show that except for a single layer of
gates during the preparation, all subsequent operations can be shifted to the
final adapted single qubit measurements. Remarkably, cluster state preparation
is achieved using essentially the same scaling in resources as if deterministic
gates were available.
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 19:18:06 GMT"
},
{
"version": "v2",
"created": "Thu, 17 May 2007 18:23:47 GMT"
},
{
"version": "v3",
"created": "Fri, 20 Jul 2007 10:38:03 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Kieling",
"K.",
""
],
[
"Rudolph",
"T.",
""
],
[
"Eisert",
"J.",
""
]
]
|
quant-ph/0611141 | Anil Shaji | Thomas F. Jordan, Anil Shaji, E. C. G. Sudarshan | One qubit almost completely reveals the dynamics of two | 6 pages with new and updated material | null | 10.1103/PhysRevA.76.012101 | null | quant-ph | null | From the time dependence of states of one of them, the dynamics of two
interacting qubits is determined to be one of two possibilities that differ
only by a change of signs of parameters in the Hamiltonian. The only exception
is a simple particular case where several parameters in the Hamiltonian are
zero and one of the remaining nonzero parameters has no effect on the time
dependence of states of the one qubit. The mean values that describe the
initial state of the other qubit and of the correlations between the two qubits
also are generally determined to within a change of signs by the time
dependence of states of the one qubit, but with many more exceptions. An
example demonstrates all the results. Feedback in the equations of motion that
allows time dependence in a subsystem to determine the dynamics of the larger
system can occur in both classical and quantum mechanics. The role of quantum
mechanics here is just to identify qubits as the simplest objects to consider
and specify the form that equations of motion for two interacting qubits can
take.
| [
{
"version": "v1",
"created": "Mon, 13 Nov 2006 21:33:48 GMT"
},
{
"version": "v2",
"created": "Mon, 21 May 2007 20:09:39 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Jordan",
"Thomas F.",
""
],
[
"Shaji",
"Anil",
""
],
[
"Sudarshan",
"E. C. G.",
""
]
]
|
quant-ph/0611142 | Kai Chen | Kai Chen, Sergio Albeverio, and Shao-Ming Fei | Two-Setting Bell Inequalities for Many Qubits | 4 pages, no figure | Phys. Rev. A 74, 050101(R) (2006) | 10.1103/PhysRevA.74.050101 | null | quant-ph | null | We present a family of Bell inequalities involving only two measurement
settings of each party for N>2 qubits. Our inequalities include all the
standard ones with fewer than N qubits and thus gives a natural generalization.
It is shown that all the Greenberger-Horne-Zeilinger states violate the
inequalities maximally, with an amount that grows exponentially as
2^{{(N-2)}/2}. The inequalities are also violated by some states that do
satisfy all the standard Bell inequalities. Remarkably, our results yield in an
efficient and simple way an implementation of nonlocality tests of many qubits
favorably within reach of the well-established technology of linear optics.
| [
{
"version": "v1",
"created": "Mon, 13 Nov 2006 22:34:07 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Chen",
"Kai",
""
],
[
"Albeverio",
"Sergio",
""
],
[
"Fei",
"Shao-Ming",
""
]
]
|
quant-ph/0611143 | James P. Crutchfield | Karoline Wiesner and James P. Crutchfield | Infinite Correlation in Measured Quantum Processes | 2 pages, 2 figures | null | null | null | quant-ph | null | We show that quantum dynamical systems can exhibit infinite correlations in
their behavior when repeatedly measured. We model quantum processes using
quantum finite-state generators and take the stochastic language they generate
as a representation of their behavior. We analyze two spin-1 quantum systems
that differ only in how they are observed. The corresponding language generated
has short-range correlation in one case and infinite correlation in the other.
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 00:30:51 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Wiesner",
"Karoline",
""
],
[
"Crutchfield",
"James P.",
""
]
]
|
quant-ph/0611144 | Hoshang Heydari | Hoshang Heydari | Geometrical structure of entangled states and secant variety | 7 pages | Quantum Information Processing 7(1) (2008) 43-50 | null | null | quant-ph | null | We show that the secant variety of the Segre variety gives useful information
about the geometrical structure of an arbitrary multipartite quantum system. In
particular, we investigate the relation between arbitrary bipartite and
three-partite entangled states and this secant variety. We also discuss the
geometry of an arbitrary general multipartite state.
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 01:59:51 GMT"
}
]
| 2008-06-05T00:00:00 | [
[
"Heydari",
"Hoshang",
""
]
]
|
quant-ph/0611145 | He Guangqiang | Guangqiang He, Jun Zhu and Guihua Zeng | Deterministic Quantum Key Distribution Using Gaussian-Modulated Squeezed
States | 7 pages, 4figures | null | 10.1088/1009-1963/15/6/025 | null | quant-ph | null | A continuous variable ping-pong scheme, which is utilized to generate
deterministically private key, is proposed. The proposed scheme is implemented
physically by using Gaussian-modulated squeezed states. The deterministic way,
i.e., no basis reconciliation between two parties, leads a two-times efficiency
comparing to the standard quantum key distribution schemes. Especially, the
separate control mode does not need in the proposed scheme so that it is
simpler and more available than previous ping-pong schemes. The attacker may be
detected easily through the fidelity of the transmitted signal, and may not be
successful in the beam splitter attack strategy.
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 02:25:32 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"He",
"Guangqiang",
""
],
[
"Zhu",
"Jun",
""
],
[
"Zeng",
"Guihua",
""
]
]
|
quant-ph/0611146 | Kimikazu Kato | Kimikazu Kato, Mayumi Oto, Hiroshi Imai, Keiko Imai | Voronoi Diagrams and a Numerical Estimation of a Quantum Channel
Capacity | Presented at 2nd Doctoral Workshop on Mathematical and Engineering
Methods in Computer Science (MEMICS 2006) | null | null | null | quant-ph | null | We give a new geometric interpretation of quantum pure states. Using
Voronoi diagrams, we reinterpret the structure of the space of pure states as
a subspace of the quantum state space. In addition to the known coincidence of
some Voronoi diagrams for one-qubit pure states, we will show that even for
mixed one-qubit states, as far as sites are given as pure states, the Voronoi
diagram with respect to some distances -- the divergence, the Bures distance,
and the Euclidean distance -- are all the same.
As to higher level pure quantum states, for the divergence, the
Fubini-Study distance, and the Bures distance, the coincidence of the
diagrams still holds, while the coincidence of the diagrams with respect to the
divergence and the Euclidean distance no longer holds. That fact has a
significant meaning when we try to apply the method used for a numerical
estimation of a one-qubit quantum channel capacity to a higher level system.
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 04:51:07 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Kato",
"Kimikazu",
""
],
[
"Oto",
"Mayumi",
""
],
[
"Imai",
"Hiroshi",
""
],
[
"Imai",
"Keiko",
""
]
]
|
quant-ph/0611147 | Boris Tsirelson | Boris Tsirelson | How often is the coordinate of a harmonic oscillator positive? | 15 pages | null | null | null | quant-ph math.PR | null | The coordinate of a harmonic oscillator is measured at a time chosen at
random among three equiprobable instants: now, after one third of the period,
or after two thirds. The (total) probability that the outcome is positive
depends on the state of the oscillator. In the classical case the probability
varies between 1/3 and 2/3, but in the quantum case -- between 0.29 and 0.71.
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 07:08:30 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Tsirelson",
"Boris",
""
]
]
|
quant-ph/0611148 | Joerg Evers | M. Macovei, J. Evers, C. H. Keitel, M. S. Zubairy | Localization of atomic ensembles via superfluorescence | 7 pages, 6 figures | Phys. Rev. A 75, 033801 (2007) | 10.1103/PhysRevA.75.033801 | null | quant-ph | null | The sub-wavelength localization of an ensemble of atoms concentrated to a
small volume in space is investigated. The localization relies on the
interaction of the ensemble with a standing wave laser field. The light
scattered in the interaction of standing wave field and atom ensemble depends
on the position of the ensemble relative to the standing wave nodes. This
relation can be described by a fluorescence intensity profile, which depends on
the standing wave field parameters, the ensemble properties, and which is
modified due to collective effects in the ensemble of nearby particles. We
demonstrate that the intensity profile can be tailored to suit different
localization setups. Finally, we apply these results to two localization
schemes. First, we show how to localize an ensemble fixed at a certain position
in the standing wave field. Second, we discuss localization of an ensemble
passing through the standing wave field.
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 09:06:06 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Macovei",
"M.",
""
],
[
"Evers",
"J.",
""
],
[
"Keitel",
"C. H.",
""
],
[
"Zubairy",
"M. S.",
""
]
]
|
quant-ph/0611149 | Omar Mustafa | Omar Mustafa and S.Habib Mazharimousavi | (1+1)-Dirac particle with position-dependent mass in complexified
Lorentz scalar interactions: effectively PT-symmetric | 11 pages, no figures, revised | Int. J. Theor. Phys. 47, 1112 (2008) | 10.1007/s10773-007-9539-3 | null | quant-ph | null | The effect of the built-in supersymmetric quantum mechanical language on the
spectrum of the (1+1)-Dirac equation, with position-dependent mass (PDM) and
complexified Lorentz scalar interactions, is re-emphasized. The signature of
the "quasi-parity" on the Dirac particles' spectra is also studied. A Dirac
particle with PDM and complexified scalar interactions of the form S(z)=S(x-ib)
(an inversely linear plus linear, leading to a PT-symmetric oscillator model),
and S(x)=S_{r}(x)+iS_{i}(x) (a PT-symmetric Scarf II model) are considered.
Moreover, a first-order intertwining differential operator and an
$\eta$-weak-pseudo-Hermiticity generator are presented and a complexified
PT-symmetric periodic-type model is used as an illustrative example.
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 09:40:52 GMT"
},
{
"version": "v2",
"created": "Sun, 4 Feb 2007 07:51:31 GMT"
},
{
"version": "v3",
"created": "Thu, 12 Apr 2007 09:54:36 GMT"
}
]
| 2008-04-04T00:00:00 | [
[
"Mustafa",
"Omar",
""
],
[
"Mazharimousavi",
"S. Habib",
""
]
]
|
quant-ph/0611150 | Dieter Heiss | D.P.Musumbu, H.B.Geyer and W.D.Heiss | Choice of a Metric for the Non-Hermitian Oscillator | to appear in J Phys A | null | null | null | quant-ph | null | The harmonic oscillator Hamiltonian, when augmented by a non-Hermitian
$\cal{PT}$-symmetric part, can be transformed into a Hermitian Hamiltonian.
This is achieved by introducing a metric which, in general, renders other
observables such as the usual momentum or position as non-Hermitian operators.
The metric depends on one real parameter, the full range of which is
investigated. The explicit functional dependence of the metric and each
associated Hamiltonian is given. A specific choice of this parameter determines
a specific combination of position and momentum as being an observable; this
can be in particular either standard position or momentum, but not both
simultaneously. Singularities of the metric are explored and their removability
is investigated. The physical significance of these findings is discussed
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 10:02:26 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Musumbu",
"D. P.",
""
],
[
"Geyer",
"H. B.",
""
],
[
"Heiss",
"W. D.",
""
]
]
|
quant-ph/0611151 | Marcos Curty | Marcos Curty, Tobias Moroder | On single-photon quantum key distribution in the presence of loss | 14 pages, 6 figures | Phys. Rev. A 75, 052336 (2007) | 10.1103/PhysRevA.75.052336 | null | quant-ph | null | We investigate two-way and one-way single-photon quantum key distribution
(QKD) protocols in the presence of loss introduced by the quantum channel. Our
analysis is based on a simple precondition for secure QKD in each case. In
particular, the legitimate users need to prove that there exists no separable
state (in the case of two-way QKD), or that there exists no quantum state
having a symmetric extension (one-way QKD), that is compatible with the
available measurements results. We show that both criteria can be formulated as
a convex optimisation problem known as a semidefinite program, which can be
efficiently solved. Moreover, we prove that the solution to the dual
optimisation corresponds to the evaluation of an optimal witness operator that
belongs to the minimal verification set of them for the given two-way (or
one-way) QKD protocol. A positive expectation value of this optimal witness
operator states that no secret key can be distilled from the available
measurements results. We apply such analysis to several well-known
single-photon QKD protocols under losses.
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 11:18:08 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Curty",
"Marcos",
""
],
[
"Moroder",
"Tobias",
""
]
]
|
quant-ph/0611152 | Roberto Passante | R. Messina, R. Passante | Casimir-Polder force density between an atom and a conducting wall | 5 pages | Phys. Rev. A 75, 042113 (2007) | 10.1103/PhysRevA.75.042113 | null | quant-ph | null | In this paper we calculate the Casimir-Polder force density (force per unit
area acting on the elements of the surface) on a metallic plate placed in front
of a neutral atom. To obtain the force density we use the quantum operator
associated to the electromagnetic stress tensor. We explicitly show that the
integral of this force density over the plate reproduces the total force acting
on the plate. This result shows that, although the force is obtained as a sum
of surface element-atom contributions, the stress-tensor method includes also
nonadditive components of Casimir-Polder forces in the evaluation of the force
acting on a macroscopic object.
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 11:34:26 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Messina",
"R.",
""
],
[
"Passante",
"R.",
""
]
]
|
quant-ph/0611153 | Yibo Zhao | Yibo Zhao | Security verification for continuous variable quantum key distribution | withdrawed | null | null | null | quant-ph | null | This paper has been withdrawn by the author
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 12:08:27 GMT"
},
{
"version": "v2",
"created": "Wed, 7 May 2008 12:38:05 GMT"
}
]
| 2008-05-07T00:00:00 | [
[
"Zhao",
"Yibo",
""
]
]
|
quant-ph/0611154 | Chen Xi | Xi Chen and Chun-Fang Li | Physical mechanism of superluminal traversal time: interference between
multiple finite wave packets | 9 pages, 3 figures, Some comments and suggestions are appreciated | EPL, 82 (2008) 30009 | 10.1209/0295-5075/82/30009 | null | quant-ph | null | The mechanism of superluminal traversal time through a potential well or
potential barrier is investigated from the viewpoint of interference between
multiple finite wave packets, due to the multiple reflections inside the well
or barrier. In the case of potential-well traveling that is classically
allowed, each of the successively transmitted constituents is delayed by a
subluminal time. When the thickness of the well is much smaller in comparision
with a characteristic length of the incident wave packet, the reshaped wave
packet in transmission maintains the profile of the incident wave packet. In
the case of potential-barrier tunneling that is classically forbidden, though
each of the successively transmitted constituents is delayed by a time that is
independent of the barrier thickness, the interference between multiple
transmitted constituents explains the barrier-thickness dependence of the
traversal time for thin barriers and its barrier-thickness independence for
thick barriers. This manifests the nature of Hartman effect.
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 14:12:08 GMT"
}
]
| 2009-03-30T00:00:00 | [
[
"Chen",
"Xi",
""
],
[
"Li",
"Chun-Fang",
""
]
]
|
quant-ph/0611155 | Astrid Lambrecht | I. Pirozhenko, A. Lambrecht, and V. B. Svetovoy | Sample dependence of the Casimir forces | 16 pages, 8 figures, uses iopart.sty | NewJ.Phys.8:238,2006 | 10.1088/1367-2630/8/10/238 | null | quant-ph hep-th | null | We have analyzed available optical data for Au in the mid-infrared range
which is important for a precise prediction of the Casimir force. Significant
variation of the data demonstrates genuine sample dependence of the dielectric
function. We demonstrate that the Casimir force is largely determined by the
material properties in the low frequency domain and argue that therefore the
precise values of the Drude parameters are crucial for an accurate evaluation
of the force. These parameters can be estimated by two different methods,
either by fitting real and imaginary parts of the dielectric function at low
frequencies, or via a Kramers-Kronig analysis based on the imaginary part of
the dielectric function in the extended frequency range. Both methods lead to
very similar results. We show that the variation of the Casimir force
calculated with the use of different optical data can be as large as 5% and at
any rate cannot be ignored. To have a reliable prediction of the force with a
precision of 1%, one has to measure the optical properties of metallic films
used for the force measurement.
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 15:31:49 GMT"
}
]
| 2008-11-26T00:00:00 | [
[
"Pirozhenko",
"I.",
""
],
[
"Lambrecht",
"A.",
""
],
[
"Svetovoy",
"V. B.",
""
]
]
|
quant-ph/0611156 | Zeph Landau | Dorit Aharonov, Zeph Landau, Johann Makowsky | The quantum FFT can be classically simulated | 12 pages, 3 figures. Added reference to similar results achieved
independently by Yoran and Short (quant-ph/0611241) | null | null | null | quant-ph | null | In this note we describe a simple and intriguing observation: the quantum
Fourier transform (QFT) over $Z_q$, which is considered the most ``quantum''
part of Shor's algorithm, can in fact be simulated efficiently by classical
computers.
More precisely, we observe that the QFT can be performed by a circuit of
poly-logarithmic path-width, if the circuit is allowed to apply not only
unitary gates but also general linear gates. Recalling the results of Markov
and Shi [MaSh] and Jozsa [Jo] which provided classical simulations of such
circuits in time exponential in the tree-width, this implies the result stated
in the title.
Classical simulations of the FFT are of course meaningless when applied to
classical input strings on which their result is already known; Our observation
might be interesting only in the context in which the QFT is used as a
subroutine and applied to more interesting superpositions. We discuss the
reasons why this idea seems to fail to provide an efficient classical
simulation of the entire factoring algorithm.
In the course of proving our observation, we provide two alternative proofs
of the results of [MaSh,Jo] which we use. One proof is very similar in spirit
to that of [MaSh] but is more visual, and is based on a graph parameter which
we call the ``bubble width'', tightly related to the path- and tree-width. The
other proof is based on connections to the Jones polynomial; It is very short,
if one is willing to rely on several known results.
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 18:31:23 GMT"
},
{
"version": "v2",
"created": "Mon, 26 Mar 2007 00:18:13 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Aharonov",
"Dorit",
""
],
[
"Landau",
"Zeph",
""
],
[
"Makowsky",
"Johann",
""
]
]
|
quant-ph/0611157 | Animesh Datta | Animesh Datta and Guifre Vidal | On the role of entanglement and correlations in mixed-state quantum
computation | null | Phys. Rev. A 75, 042310 (2007) | 10.1103/PhysRevA.75.042310 | null | quant-ph | null | In a quantum computation with pure states, the generation of large amounts of
entanglement is known to be necessary for a speedup with respect to classical
computations. However, examples of quantum computations with mixed states are
known, such as the deterministic computation with one quantum qubit (DQC1)
model [Knill and Laflamme, Phys. Rev. Lett. 81, 5672 (1998)], in which
entanglement is at most marginally present, and yet a computational speedup is
believed to occur. Correlations, and not entanglement, have been identified as
a necessary ingredient for mixed-state quantum computation speedups. Here we
show that correlations, as measured through the operator Schmidt rank, are
indeed present in large amounts in the DQC1 circuit. This provides evidence for
the preclusion of efficient classical simulation of DQC1 by means of a whole
class of classical simulation algorithms, thereby reinforcing the conjecture
that DQC1 leads to a genuine quantum computational speedup.
| [
{
"version": "v1",
"created": "Tue, 14 Nov 2006 21:08:21 GMT"
},
{
"version": "v2",
"created": "Thu, 12 Apr 2007 04:38:55 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Datta",
"Animesh",
""
],
[
"Vidal",
"Guifre",
""
]
]
|
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.