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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
quant-ph/0612063 | Julia Kempe | Julia Kempe and Thomas Vidick | On the Power of Entangled Quantum Provers | 17 pages | null | null | null | quant-ph | null | We show that the value of a general two-prover quantum game cannot be
computed by a semi-definite program ofvpolynomial size (unless P=NP), a method
that has been successful in more restricted quantum games. More precisely, we
show that proof of membership in the NP-complete problem GAP-3D-Matching can be
obtained by a 2-prover, 1-round quantum interactive proof system where the
provers share entanglement, with perfect completeness and soundness
s=1-2^(-O(n)), and such that the space of the verifier and the size of the
messages are O(log n). This implies that QMIP^*_{log n,1,1-2^(-O(n))}
\nsubseteq P unless P = NP and provides the first non-trivial lower bound on
the power of entangled quantum provers, albeit with an exponentially small gap.
The gap achievable by our proof system might in fact be larger, provided a
certain conjecture on almost commuting versus nearly commuting projector
matrices is true.
| [
{
"version": "v1",
"created": "Fri, 8 Dec 2006 17:06:34 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Kempe",
"Julia",
""
],
[
"Vidick",
"Thomas",
""
]
]
|
quant-ph/0612064 | Roland Hildebrand | Roland Hildebrand | Concurrence of Lorentz-positive maps | 13 pages, 25 small figures | null | null | null | quant-ph | null | Let L_n be the n-dimensional Lorentz cone. A linear map M from R^m to R^n is
called Lorentz-positive if M[L_m] is contained in L_n. We extend the notion of
concurrence, which was initially introduced to quantify the entanglement of
bipartite density matrices, to Lorentz-positive maps and provide an explicite
formula for it. This allows us to obtain formulae for the concurrence of
arbitrary positive operators taking 2 x 2 complex hermitian matrices as input
and consequently of arbitrary bipartite density matrices of rank 2. Namely, let
P: H(2) \to H(d) be a positive operator, and let \lambda_1,...,\lambda_4 be the
generalized eigenvalues of the pencil \sigma_2(P(X)) - \lambda det X, in
decreasing order, where \sigma_2 is the second symmetric function of the
spectrum. Then the concurrence is given by the expression C(P;X) =
2\sqrt{\sigma_2(P(X)) - \lambda_2 det X}. As an application, we compute the
concurrences of the density matrices of all graphs with 2 edges. Similar
results apply for a function which we call I-fidelity, with the second largest
generalized eigenvalue \lambda_2 replaced by the smallest eigenvalue \lambda_4.
| [
{
"version": "v1",
"created": "Fri, 8 Dec 2006 15:48:43 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Hildebrand",
"Roland",
""
]
]
|
quant-ph/0612065 | Robert B. Griffiths | Robert B. Griffiths | Quantum mechanics without measurements | Latex 22 pages, 3 figures in text using PSTricks | null | null | null | quant-ph | null | Many of the conceptual problems students have in understanding quantum
mechanics arise from the way probabilities are introduced in standard
(textbook) quantum theory through the use of measurements. Introducing
consistent microscopic probabilities in quantum theory requires setting up
appropriate sample spaces taking proper account of quantum incompatibility.
When this is done the Schrodinger equation can be used to calculate
probabilities independent of whether a system is or is not being measured, and
the results usually ascribed to wave function collapse are obtained in a less
misleading way through conditional probabilities. Toy models that include
measurement apparatus as part of the total quantum system make this approach
accessible to students. Some comments are made about teaching this material.
| [
{
"version": "v1",
"created": "Fri, 8 Dec 2006 19:13:18 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Griffiths",
"Robert B.",
""
]
]
|
quant-ph/0612066 | Fei Gao | Song Lin, Fei Gao, Fen-Zhuo Guo, Qiao-Yan Wen, Fu-Chen Zhu | Improving the security of multiparty quantum secret sharing based on
entanglement swapping against participant attack | 6 pages, 3 figures | null | null | null | quant-ph | null | In a recent paper [Z. J. Zhang and Z. X. Man, Phys. Rev. A 72, 022303(2005)],
a multiparty quantum secret sharing protocol based on entanglement swapping was
presented. However, as we show, this protocol is insecure in the sense that an
unauthorized agent group can recover the secret from the dealer. Hence, we
propose an improved version of this protocol which can stand against this kind
of attack.
| [
{
"version": "v1",
"created": "Sat, 9 Dec 2006 13:49:29 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Lin",
"Song",
""
],
[
"Gao",
"Fei",
""
],
[
"Guo",
"Fen-Zhuo",
""
],
[
"Wen",
"Qiao-Yan",
""
],
[
"Zhu",
"Fu-Chen",
""
]
]
|
quant-ph/0612067 | Alexandre Dodonov V | A. V. Dodonov, S. S. Mizrahi, and V. V. Dodonov | Continuous photodetection model: quantum jump engineering and hints for
experimental verification | 12 pages, 7 figures. Contribution to the conference Quantum Optics
III, Pucon - Chile, November 27-30, 2006 | Journal of Physics: Conference Series 84, 012005 (2007) | 10.1088/1742-6596/84/1/012005 | null | quant-ph | null | We examine some aspects of the continuous photodetection model for
photocounting processes in cavities. First, we work out a microscopic model
that describes the field-detector interaction and deduce a general expression
for the Quantum Jump Superoperator (QJS), that shapes the detector's
post-action on the field upon a detection. We show that in particular cases our
model recovers the QJSs previously proposed ad hoc in the literature and point
out that by adjusting the detector parameters one can engineer QJSs. Then we
set up schemes for experimental verification of the model. By taking into
account the ubiquitous non-idealities, we show that by measuring the lower
photocounts moments and the mean waiting time one can check which QJS better
describes the photocounting phenomenon.
| [
{
"version": "v1",
"created": "Sat, 9 Dec 2006 23:09:26 GMT"
},
{
"version": "v2",
"created": "Fri, 2 Feb 2007 03:42:37 GMT"
}
]
| 2009-06-17T00:00:00 | [
[
"Dodonov",
"A. V.",
""
],
[
"Mizrahi",
"S. S.",
""
],
[
"Dodonov",
"V. V.",
""
]
]
|
quant-ph/0612068 | An Min Wang | An Min Wang | Quantum mechanics in general quantum systems (IV): Green operator and
path integral | 6 pages, no figure. This is the fourth preprint in our serial
studies. The previous three preprints are, respectively, quant-ph/0611216,
quant-ph/0611217 and quant-ph/0601051 | null | null | null | quant-ph cond-mat.other | null | We first rewrite the perturbation expansion of the time evolution operator
[An Min Wang, quant-ph/0611216] in a form as concise as possible. Then we
derive out the perturbation expansion of the time-dependent complete Green
operator and prove that it is just the Fourier transformation of the Dyson
equation. Moreover, we obtain the perturbation expansion of the complete
transition amplitude in the Feynman path integral formulism, and give an
integral expression that relates the complete transition amplitude with the
unperturbed transition amplitude. Further applications of these results can be
expected and will be investigated in the near future.
| [
{
"version": "v1",
"created": "Sun, 10 Dec 2006 12:53:30 GMT"
},
{
"version": "v2",
"created": "Mon, 11 Dec 2006 23:49:23 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Wang",
"An Min",
""
]
]
|
quant-ph/0612069 | Wang Zhi Yong | Zhi-Yong Wang, Cai-Dong Xiong, Bing He | Alternative perspective on photonic tunneling | 24 pages, Revised version based on PRA75,013813(2007) | Physical Review A 75, 013813 (2007) | 10.1103/PhysRevA.75.013813 | null | quant-ph | null | A relativistic quantum-mechanical description of guided waves is given, based
on which we present an alternative way to describe and interpret the
propagation of electromagnetic wave packets through an undersized waveguide. In
particular, we show that the superluminal phenomenon of evanescent modes is
actually a known conclusion in quantum field theory, and it preserves a
quantum-mechanical causality.
| [
{
"version": "v1",
"created": "Sun, 10 Dec 2006 14:14:29 GMT"
},
{
"version": "v2",
"created": "Tue, 9 Jan 2007 09:55:02 GMT"
},
{
"version": "v3",
"created": "Thu, 11 Jan 2007 03:44:49 GMT"
},
{
"version": "v4",
"created": "Sun, 28 Jan 2007 13:55:51 GMT"
},
{
"version": "v5",
"created": "Thu, 1 Mar 2007 12:16:55 GMT"
},
{
"version": "v6",
"created": "Mon, 23 Apr 2007 12:34:37 GMT"
},
{
"version": "v7",
"created": "Sat, 9 Jun 2007 11:14:42 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Wang",
"Zhi-Yong",
""
],
[
"Xiong",
"Cai-Dong",
""
],
[
"He",
"Bing",
""
]
]
|
quant-ph/0612070 | Jeffrey H. Shapiro | Baris I. Erkmen and Jeffrey H. Shapiro | Ghost Imaging: What is quantum, what is not | 4 pages, 2 figures | null | null | null | quant-ph | null | We provide a unified treatment of classical and quantum Gaussian-state
sources that unambiguously identifies which features of ghost imaging are
strictly quantum mechanical. We show that ghost-image formation is
fundamentally classical, with the image being expressible in terms of the
phase-insensitive and phase-sensitive cross correlations between the detected
fields. We then consider ghost-imaging scenarios with either phase-insensitive
or phase-sensitive sources, where the former are always classical but the
latter may be classical or quantum mechanical. We show that if their
auto-correlations are identical, then a quantum source provides resolution
improvement in its near-field and field-of-view improvement in its far field
when compared to a classical source.
| [
{
"version": "v1",
"created": "Sun, 10 Dec 2006 14:55:22 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Erkmen",
"Baris I.",
""
],
[
"Shapiro",
"Jeffrey H.",
""
]
]
|
quant-ph/0612071 | Guang Ping He | Guang Ping He | Comment on "Quantum string seal is insecure" | 2 pages | Phys. Rev. A 76, 056301 (2007) | 10.1103/PhysRevA.76.056301 | null | quant-ph | null | Recently an attack strategy was proposed by Chau [H. F. Chau,
quant-ph/0602099 v3], which was claimed to be able to break all quantum string
seal protocols, including the one proposed by He [G. P. He, Int. J. Quant.
Inform. 4, 677 (2006)]. Here it will be shown that the information obtained in
He's protocol by the attack is trivial. Thus Chau's conclusion that all quantum
string seals are insecure is wrong. It will also be shown that some other
claims in Chau's paper are inaccurate either.
| [
{
"version": "v1",
"created": "Sun, 10 Dec 2006 19:10:11 GMT"
}
]
| 2007-11-19T00:00:00 | [
[
"He",
"Guang Ping",
""
]
]
|
quant-ph/0612072 | Lieven Clarisse | Lieven Clarisse | Entanglement Distillation; A Discourse on Bound Entanglement in Quantum
Information Theory | 192 pages | null | null | null | quant-ph | null | PhD thesis (University of York). The thesis covers in a unified way the
material presented in quant-ph/0403073, quant-ph/0502040, quant-ph/0504160,
quant-ph/0510035, quant-ph/0512012 and quant-ph/0603283. It includes two large
review chapters on entanglement and distillation.
| [
{
"version": "v1",
"created": "Sun, 10 Dec 2006 20:52:42 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Clarisse",
"Lieven",
""
]
]
|
quant-ph/0612073 | Jaeyoon Cho | Jaeyoon Cho | Fault-tolerant linear optics quantum computation by error-detecting
quantum state transfer | 9 pages, 7 figures | Phys. Rev. A 76, 042311 (2007) | 10.1103/PhysRevA.76.042311 | null | quant-ph | null | A scheme for linear optical implementation of fault-tolerant quantum
computation is proposed, which is based on an error-detecting code. Each
computational step is mediated by transfer of quantum information into an
ancilla system embedding error-detection capability. Photons are assumed to be
subjected to both photon loss and depolarization, and the threshold region of
their strengths for scalable quantum computation is obtained, together with the
amount of physical resources consumed. Compared to currently known results, the
present scheme reduces the resource requirement, while yielding a comparable
threshold region.
| [
{
"version": "v1",
"created": "Mon, 11 Dec 2006 06:03:38 GMT"
},
{
"version": "v2",
"created": "Mon, 23 Jul 2007 08:35:38 GMT"
},
{
"version": "v3",
"created": "Sun, 7 Oct 2007 14:19:36 GMT"
}
]
| 2007-10-07T00:00:00 | [
[
"Cho",
"Jaeyoon",
""
]
]
|
quant-ph/0612074 | Tom Boness | T. Boness, M.M.A. Stocklin and T.S. Monteiro | Quantum chaos with spin-chains in pulsed magnetic fields | 10 pages, 4 figures. Submitted to PTP special issue for QMC2006 | null | 10.1143/PTPS.166.85 | null | quant-ph | null | Recently it was found that the dynamics in a Heisenberg spin-chain subjected
to a sequence of periodic pulses from an external, parabolic, magnetic field
can have a close correspondence with the quantum kicked rotor (QKR). The QKR is
a key paradigm of quantum chaos; it has as its classical limit the well-known
Standard Map. It was found that a single spin excitation could be converted
into a pair of non-dispersive, counter-propagating spin coherent states
equivalent to the accelerator modes of the Standard Map. Here we consider how
other types of quantum chaotic systems such as a double-kicked quantum rotor or
a quantum rotor with a double-well potential might be realized with spin
chains; we discuss the possibilities regarding manipulation of the one-magnon
spin waves.
| [
{
"version": "v1",
"created": "Mon, 11 Dec 2006 13:43:57 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Boness",
"T.",
""
],
[
"Stocklin",
"M. M. A.",
""
],
[
"Monteiro",
"T. S.",
""
]
]
|
quant-ph/0612075 | Marco Genovese | Giorgio Brida, Marco Genovese, Marco Gramegna, Fabrizio Piacentini,
Enrico Predazzi, Ivano Ruo-Berchera | Experimental tests of hidden variable theories from dBB to Stochastic
Electrodynamics | null | Journal of Physics: Conference Series 67 (2007) 012047 | 10.1088/1742-6596/67/1/012047 | null | quant-ph | null | In this paper we present some of our experimental results on testing hidden
variable theories, which range from Bell inequalities measurements to a
conclusive test of stochastic electrodynamics.
| [
{
"version": "v1",
"created": "Mon, 11 Dec 2006 13:40:57 GMT"
}
]
| 2007-06-13T00:00:00 | [
[
"Brida",
"Giorgio",
""
],
[
"Genovese",
"Marco",
""
],
[
"Gramegna",
"Marco",
""
],
[
"Piacentini",
"Fabrizio",
""
],
[
"Predazzi",
"Enrico",
""
],
[
"Ruo-Berchera",
"Ivano",
""
]
]
|
quant-ph/0612076 | Miodrag Krmar | Vladan Pankovi\'c, Milan Predojevi\'c | A Variant and Explanation of the Delayed Choice Experiment | 9 pages, no figures | null | null | NS-PH-28/06 | quant-ph | null | In this work we suggest a variant of the remarkable Wheeler's delayed choice
gedanken experiment. In our experiment, single photon described by a
superposition state with two terms dynamically interacts with an atom.
Preparation of the atom in any of two excited states can be realized
practically in the last moment before interaction. For atom in the first
excited state there is practically none dynamical interaction between atom and
photon so that the interference effects on the photon can be detected later by
a photo plate. For atom in the second excited state dynamical interaction
between photon and atom causes certainly the stimulated emission of a new
photon that moves coherently with the first photon. Both photons do a
super-system described by an entangled quantum state. But in this case photo
plate, that realizes simultaneously sub-systemic measurement at any photon,
does not detect interference effects. We suggest a simple explanation of given
as well as original variant of the delayed choice experiment in full agreement
with standard quantum mechanical formalism.
| [
{
"version": "v1",
"created": "Mon, 11 Dec 2006 14:04:06 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Panković",
"Vladan",
""
],
[
"Predojević",
"Milan",
""
]
]
|
quant-ph/0612077 | John Cooper w | John W. Cooper | A Re-evaluation of Shor's Algorithm | 15 pages | null | null | null | quant-ph | null | Shor's algorithm is examined critically from the standpoint of it's eventual
use to obtain the factors of large integers.
| [
{
"version": "v1",
"created": "Mon, 11 Dec 2006 16:07:40 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Cooper",
"John W.",
""
]
]
|
quant-ph/0612078 | Klaus Hornberger | Klaus Hornberger | Monitoring approach to open quantum dynamics using scattering theory | 5 pages; published version | EPL 77, 50007 (2007) | 10.1209/0295-5075/77/50007 | null | quant-ph | null | It is shown how S-matrix theory and the concept of continuous quantum
measurements can be combined to yield Markovian master equations which describe
the environmental interaction non-perturbatively. The method is then applied to
obtain the master equation for the effects of a gas on the internal dynamics of
an immobile complex quantum system, such as a trapped molecule, in terms of the
exact multi-channel scattering amplitudes.
| [
{
"version": "v1",
"created": "Mon, 11 Dec 2006 20:00:13 GMT"
},
{
"version": "v2",
"created": "Thu, 22 Feb 2007 18:01:01 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Hornberger",
"Klaus",
""
]
]
|
quant-ph/0612079 | Luis Roa Oppliger | L. Roa, R. Pozo-Gonzalez, M. Schaefer, P. Utreras-SM | Narrow entanglement beats | six pages and two figure included | null | null | null | quant-ph | null | We study how the entanglement between two atoms can be created or modified
even when they do not interact but when each of them interacts dispersively,
i.e., weak and far from the resonance with a single mode of the field.
Considering that regime we apply a method which makes use of a small nonlinear
deformation of the usual SU(2) algebra in order to obtain the effective
Hamiltonian describing correctly the dynamics for any initial states. In
particular we study two cases: In the first one we consider each atom initially
in a pure state and in the second case we assume that they start in a Werner
state. We find that both atoms can reach, periodically, maximum entanglement if
each of them starts in any eigenstate of the x-componet of the Pauli oprator,
independent of the initial Fock state of the mode. Thus we find that a
dispersive vacuum can generate entanglement between two two-level atoms. In the
second case and when the field mode is initially in a coherent or thermal
state, we find that in the high energy limit, in general, there is no
entanglement between the two atoms however at well defined moments the initial
entanglement is as suddenly recovered as removed. This time behavior looks like
narrow beats separated by the so called entanglement dead valleys.
| [
{
"version": "v1",
"created": "Mon, 11 Dec 2006 20:20:16 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Roa",
"L.",
""
],
[
"Pozo-Gonzalez",
"R.",
""
],
[
"Schaefer",
"M.",
""
],
[
"Utreras-SM",
"P.",
""
]
]
|
quant-ph/0612080 | Mark A. Rubin | Mark A. Rubin and Sumanth Kaushik | Loss-Induced Limits to Phase Measurement Precision with Maximally
Entangled States | Additional references included | Phys. Rev. A 75 (2007) 053805 | 10.1103/PhysRevA.75.053805 | WW-12938 | quant-ph | null | The presence of loss limits the precision of an approach to phase measurement
using maximally entangled states, also referred to as NOON states. A
calculation using a simple beam-splitter model of loss shows that, for all
nonzero values L of the loss, phase measurement precision degrades with
increasing number N of entangled photons for N sufficiently large. For L above
a critical value of approximately 0.785, phase measurement precision degrades
with increasing N for all values of N. For L near zero, phase measurement
precision improves with increasing N down to a limiting precision of
approximately 1.018 L radians, attained at N approximately equal to 2.218/L,
and degrades as N increases beyond this value. Phase measurement precision with
multiple measurements and a fixed total number of photons N_T is also examined.
For L above a critical value of approximately 0.586, the ratio of phase
measurement precision attainable with NOON states to that attainable by
conventional methods using unentangled coherent states degrades with increasing
N, the number of entangled photons employed in a single measurement, for all
values of N. For L near zero this ratio is optimized by using approximately
N=1.279/L entangled photons in each measurement, yielding a precision of
approximately 1.340 sqrt(L/N_T) radians.
| [
{
"version": "v1",
"created": "Mon, 11 Dec 2006 21:16:42 GMT"
},
{
"version": "v2",
"created": "Fri, 26 Jan 2007 20:50:19 GMT"
},
{
"version": "v3",
"created": "Fri, 26 Jan 2007 21:33:46 GMT"
},
{
"version": "v4",
"created": "Thu, 8 Mar 2007 15:02:56 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Rubin",
"Mark A.",
""
],
[
"Kaushik",
"Sumanth",
""
]
]
|
quant-ph/0612081 | Robert Adamson | R. B. A. Adamson, P. S. Turner, M. W. Mitchell and A. M. Steinberg | Detecting Hidden Differences via Permutation Symmetries | 8 pages, 1 figure | null | 10.1103/PhysRevA.78.033832 | null | quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present a method for describing and characterizing the state of N
particles that may be distinguishable in principle but not in practice due to
experimental limitations. The technique relies upon a careful treatment of the
exchange symmetry of the state among experimentally accessible and
experimentally inaccessible degrees of freedom. The approach we present allows
a new formalisation of the notion of indistinguishability and can be
implemented easily using currently available experimental techniques. Our work
is of direct relevance to current experiments in quantum optics, for which we
provide a specific implementation.
| [
{
"version": "v1",
"created": "Mon, 11 Dec 2006 21:20:12 GMT"
},
{
"version": "v2",
"created": "Thu, 14 Dec 2006 19:00:02 GMT"
},
{
"version": "v3",
"created": "Fri, 15 Dec 2006 22:11:17 GMT"
},
{
"version": "v4",
"created": "Sun, 23 Dec 2007 00:07:08 GMT"
},
{
"version": "v5",
"created": "Mon, 4 Aug 2008 22:10:01 GMT"
}
]
| 2013-05-29T00:00:00 | [
[
"Adamson",
"R. B. A.",
""
],
[
"Turner",
"P. S.",
""
],
[
"Mitchell",
"M. W.",
""
],
[
"Steinberg",
"A. M.",
""
]
]
|
quant-ph/0612082 | Alexey Gorshkov | Alexey V. Gorshkov, Axel Andre, Mikhail D. Lukin, Anders S. Sorensen | Photon storage in Lambda-type optically dense atomic media. I. Cavity
model | 16 pages, 2 figures. V2: significant changes in presentation, new
references, higher resolution of figures | Phys. Rev. A 76, 033804 (2007) | 10.1103/PhysRevA.76.033804 | null | quant-ph | null | In a recent paper [Gorshkov et al., Phys. Rev. Lett. 98, 123601 (2007)], we
used a universal physical picture to optimize and demonstrate equivalence
between a wide range of techniques for storage and retrieval of photon wave
packets in Lambda-type atomic media in free space, including the adiabatic
reduction of the photon group velocity, pulse-propagation control via
off-resonant Raman techniques, and photon-echo-based techniques. In the present
paper, we perform the same analysis for the cavity model. In particular, we
show that the retrieval efficiency is equal to C/(1+C) independent of the
retrieval technique, where C is the cooperativity parameter. We also derive the
optimal strategy for storage and, in particular, demonstrate that at any
detuning one can store, with the optimal efficiency of C/(1+C), any smooth
input mode satisfying T C gamma >> 1 and a certain class of resonant input
modes satisfying T C gamma ~ 1, where T is the duration of the input mode and 2
gamma is the transition linewidth. In the two subsequent papers of the series,
we present the full analysis of the free-space model and discuss the effects of
inhomogeneous broadening on photon storage.
| [
{
"version": "v1",
"created": "Mon, 11 Dec 2006 23:22:18 GMT"
},
{
"version": "v2",
"created": "Sat, 8 Sep 2007 21:13:12 GMT"
}
]
| 2007-09-09T00:00:00 | [
[
"Gorshkov",
"Alexey V.",
""
],
[
"Andre",
"Axel",
""
],
[
"Lukin",
"Mikhail D.",
""
],
[
"Sorensen",
"Anders S.",
""
]
]
|
quant-ph/0612083 | Alexey Gorshkov | Alexey V. Gorshkov, Axel Andre, Mikhail D. Lukin, Anders S. Sorensen | Photon storage in Lambda-type optically dense atomic media. II.
Free-space model | 26 pages, 8 figures. V2: significant changes in presentation, new
references, higher resolution of figures | Phys. Rev. A 76, 033805 (2007) | 10.1103/PhysRevA.76.033805 | null | quant-ph | null | In a recent paper [Gorshkov et al., Phys. Rev. Lett. 98, 123601 (2007)], we
presented a universal physical picture for describing a wide range of
techniques for storage and retrieval of photon wave packets in Lambda-type
atomic media in free space, including the adiabatic reduction of the photon
group velocity, pulse-propagation control via off-resonant Raman techniques,
and photon-echo based techniques. This universal picture produced an optimal
control strategy for photon storage and retrieval applicable to all approaches
and yielded identical maximum efficiencies for all of them. In the present
paper, we present the full details of this analysis as well some of its
extensions, including the discussion of the effects of non-degeneracy of the
two lower levels of the Lambda system. The analysis in the present paper is
based on the intuition obtained from the study of photon storage in the cavity
model in the preceding paper [Gorshkov et al., Phys. Rev. A 76, 033804 (2007)].
| [
{
"version": "v1",
"created": "Mon, 11 Dec 2006 23:30:38 GMT"
},
{
"version": "v2",
"created": "Sat, 8 Sep 2007 21:57:00 GMT"
}
]
| 2007-09-09T00:00:00 | [
[
"Gorshkov",
"Alexey V.",
""
],
[
"Andre",
"Axel",
""
],
[
"Lukin",
"Mikhail D.",
""
],
[
"Sorensen",
"Anders S.",
""
]
]
|
quant-ph/0612084 | Alexey Gorshkov | Alexey V. Gorshkov, Axel Andre, Mikhail D. Lukin, Anders S. Sorensen | Photon storage in Lambda-type optically dense atomic media. III. Effects
of inhomogeneous broadening | 15 pages, 8 figures. V2: minor changes in presentation, new
references, higher resolution of figures | Phys. Rev. A 76, 033806 (2007) | 10.1103/PhysRevA.76.033806 | null | quant-ph | null | In a recent paper [Gorshkov et al., Phys. Rev. Lett. 98, 123601 (2007)] and
in the two preceding papers [Gorshkov et al., Phys. Rev. A 76, 033804 (2007);
76, 033805 (2007)], we used a universal physical picture to optimize and
demonstrate equivalence between a wide range of techniques for storage and
retrieval of photon wave packets in homogeneously broadened Lambda-type atomic
media, including the adiabatic reduction of the photon group velocity,
pulse-propagation control via off-resonant Raman techniques, and
photon-echo-based techniques. In the present paper, we generalize this
treatment to include inhomogeneous broadening. In particular, we consider the
case of Doppler-broadened atoms and assume that there is a negligible
difference between the Doppler shifts of the two optical transitions. In this
situation, we show that, at high enough optical depth, all atoms contribute
coherently to the storage process as if the medium were homogeneously
broadened. We also discuss the effects of inhomogeneous broadening in solid
state samples. In this context, we discuss the advantages and limitations of
reversing the inhomogeneous broadening during the storage time, as well as
suggest a way for achieving high efficiencies with a nonreversible
inhomogeneous profile.
| [
{
"version": "v1",
"created": "Mon, 11 Dec 2006 23:39:10 GMT"
},
{
"version": "v2",
"created": "Sat, 8 Sep 2007 23:18:11 GMT"
}
]
| 2007-09-09T00:00:00 | [
[
"Gorshkov",
"Alexey V.",
""
],
[
"Andre",
"Axel",
""
],
[
"Lukin",
"Mikhail D.",
""
],
[
"Sorensen",
"Anders S.",
""
]
]
|
quant-ph/0612085 | Marek Szcz\c{e}sny | Marek Szczesny | Randomized and Quantum Solution of Initial-Value Problems for Ordinary
Differential Equations of Order k | null | null | null | null | quant-ph | null | We study possible advantages of randomized and quantum computing over
deterministic computing for scalar initial-value problems for ordinary
differential equations of order k. For systems of equations of the first order
this question has been settled modulo some details in \cite{Kacewicz05}. A
speed-up over deterministic computing shown in \cite{Kacewicz05} is related to
the increased regularity of the solution with respect to that of the right-hand
side function. For a scalar equation of order k (which can be transformed into
a special system of the first order), the regularity of the solution is
increased by k orders of magnitude. This leads to improved complexity bounds
depending on k for linear information in the deterministic setting, see
\cite{Szczesny05}. This may suggest that in the randomized and quantum settings
a speed-up can also be achieved depending on k.
We show in this paper that a speed-up dependent on k is not possible in the
randomized and quantum settings. We establish lower complexity bounds, showing
that the randomized and quantum complexities remain at the some level as for
systems of the first order, no matter how large k is. Thus, the algorithms from
\cite{Kacewicz05} remain (almost) optimal, even if we restrict ourselves to a
subclass of systems arising from scalar equations of order k.
| [
{
"version": "v1",
"created": "Wed, 13 Dec 2006 00:09:04 GMT"
},
{
"version": "v2",
"created": "Tue, 19 Dec 2006 23:12:31 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Szczesny",
"Marek",
""
]
]
|
quant-ph/0612086 | Jeffrey H. Shapiro | Jeffrey H. Shapiro and Mohsen Razavi | Continuous-time cross-phase modulation and quantum computation | 17 pages, 5 figures; values of C and D corrected in equation (45);
new figures 3, 4, and 5 | null | 10.1088/1367-2630/9/1/016 | null | quant-ph | null | The weak nonlinear Kerr interaction between single photons and intense laser
fields has been recently proposed as a basis for distributed optics-based
solutions to few-qubit applications in quantum communication and computation.
Here, we analyze the above Kerr interaction by employing a continuous-time
multi-mode model for the input/output fields to/from the nonlinear medium. In
contrast to previous single-mode treatments of this problem, our analysis takes
into account the full temporal content of the free-field input beams as well as
the non-instantaneous response of the medium. The main implication of this
model, in which the cross-Kerr phase shift on one input is proportional to the
photon flux of the other input, is the existence of phase noise terms at the
output. We show that these phase noise terms will preclude satisfactory
performance of the parity gate proposed by Munro, Nemoto, and Spiller [New J.
Phys. 7, 137 (2005)].
| [
{
"version": "v1",
"created": "Tue, 12 Dec 2006 01:31:56 GMT"
},
{
"version": "v2",
"created": "Thu, 28 Dec 2006 15:00:17 GMT"
},
{
"version": "v3",
"created": "Tue, 23 Jan 2007 18:34:42 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Shapiro",
"Jeffrey H.",
""
],
[
"Razavi",
"Mohsen",
""
]
]
|
quant-ph/0612087 | Xiaolong Su | Xiaolong Su, Jietai Jing, Qing Pan, and Changde Xie | Dense-coding quantum key distribution based on continuous-variable
entanglement | null | Phys. Rev. A 74,062305 (2006) | 10.1103/PhysRevA.74.062305 | null | quant-ph | null | We proposed a scheme of continuous-variable quantum key distribution, in
which the bright Einstein-Podolsky-Rosen entangled optical beams are utilized.
The source of the entangled beams is placed inside the receiving station, where
half of the entangled beams are transmitted with round trip and the other half
are retained by the receiver. The amplitude and phase signals modulated on the
signal beam by the sender are simultaneously extracted by the authorized
receiver with the scheme of the dense-coding correlation measurement for
continuous quantum variables, thus the channel capacity is significantly
improved. Two kinds of possible eavesdropping are discussed. The mutual
information and the secret key rates are calculated and compared with those of
unidirectional transmission schemes.
| [
{
"version": "v1",
"created": "Tue, 12 Dec 2006 02:39:24 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Su",
"Xiaolong",
""
],
[
"Jing",
"Jietai",
""
],
[
"Pan",
"Qing",
""
],
[
"Xie",
"Changde",
""
]
]
|
quant-ph/0612088 | Libin Fu | Jie Liu, Li-Bin Fu | Singularity of Berry Connections Inhibits the Accuracy of Adiabatic
Approximation | 5 pages, 5 figures | Physics Letters A 370, 17(2007) | 10.1016/j.physleta.2007.05.021 | null | quant-ph | null | Adiabatic approximation for quantum evolution is investigated quantitatively
with addressing its dependence on the Berry connections. We find that, in the
adiabatic limit, the adiabatic fidelity may uniformly converge to unit or
diverge manifesting the breakdown of adiabatic approximation, depending on the
type of the singularity of the Berry connections as the functions of
slowly-varying parameter $R$. When the Berry connections have a singularity of
$1/R^\sigma$ type with $\sigma < 1$, the adiabatic fidelity converges to unit
in a power-law; whereas when the singularity index $\sigma$ is larger than one,
adiabatic approximation breaks down. Two-level models are used to substantiate
our theory.
| [
{
"version": "v1",
"created": "Tue, 12 Dec 2006 02:59:14 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Liu",
"Jie",
""
],
[
"Fu",
"Li-Bin",
""
]
]
|
quant-ph/0612089 | Piotr Sniady | Cristopher Moore, Alexander Russell, Piotr Sniady | On the impossibility of a quantum sieve algorithm for graph isomorphism:
unconditional results | An earlier preprint, quant-ph/0609138, gave versions of these results
which were conditional on a group-theoretic conjecture. This version provides
unconditional results | In: STOC '07: Proceedings of the thirty-ninth annual ACM symposium
on Theory of computing, pages 536-545, New York, NY, USA, 2007. ACM Press | 10.1145/1250790.1250868 | null | quant-ph math.RT | null | It is known that any quantum algorithm for Graph Isomorphism that works
within the framework of the hidden subgroup problem (HSP) must perform highly
entangled measurements across \Omega(n \log n) coset states. One of the only
known models for how such a measurement could be carried out efficiently is
Kuperberg's algorithm for the HSP in the dihedral group, in which quantum
states are adaptively combined and measured according to the decomposition of
tensor products into irreducible representations. This ``quantum sieve'' starts
with coset states, and works its way down towards representations whose
probabilities differ depending on, for example, whether the hidden subgroup is
trivial or nontrivial.
In this paper we show that no such approach can produce a polynomial-time
quantum algorithm for Graph Isomorphism. Specifically, we consider the natural
reduction of Graph Isomorphism to the HSP over the the wreath product S_n\wr
Z_2. Using a recently proved bound on the irreducible characters of S_n, we
show that no algorithm in this family can solve Graph Isomorphism in less than
e^{\Omega(\sqrt{n})} time, no matter what adaptive rule it uses to select and
combine quantum states. In particular, algorithms of this type can offer
essentially no improvement over the best known classical algorithms, which run
in time e^{O(\sqrt{n \log n})}.
| [
{
"version": "v1",
"created": "Tue, 12 Dec 2006 08:12:34 GMT"
},
{
"version": "v2",
"created": "Mon, 18 Dec 2006 07:33:06 GMT"
},
{
"version": "v3",
"created": "Sat, 7 Apr 2007 06:15:04 GMT"
}
]
| 2007-10-18T00:00:00 | [
[
"Moore",
"Cristopher",
""
],
[
"Russell",
"Alexander",
""
],
[
"Sniady",
"Piotr",
""
]
]
|
quant-ph/0612090 | Wang Zhi Yong | Zhi-Yong Wang, Cai-Dong Xiong | Zitterbewegung at the level of quantum field theory | 10 pages, no figure, to be published in Chinese Physics | Chin. Phys. B 17 (11), 4170 (2008) | null | null | quant-ph | null | Traditionally, the zitterbewegung (ZB) of the Dirac electron has just been
studied at the level of quantum mechanics. Seeing that the fact that an old
interest in ZB has recently been rekindled by the investigations on spintronic,
graphene, and superconducting systems, etc., in this paper we present a
quantum-field-theory investigation on ZB and obtain the conclusion that, the ZB
of an electron arises from the influence of virtual electron-positron pairs (or
vacuum fluctuations) on the electron.
| [
{
"version": "v1",
"created": "Tue, 12 Dec 2006 13:07:01 GMT"
},
{
"version": "v2",
"created": "Tue, 9 Jan 2007 10:42:12 GMT"
},
{
"version": "v3",
"created": "Sun, 14 Jan 2007 14:49:55 GMT"
},
{
"version": "v4",
"created": "Thu, 22 Mar 2007 09:52:05 GMT"
},
{
"version": "v5",
"created": "Mon, 6 Aug 2007 12:42:13 GMT"
},
{
"version": "v6",
"created": "Mon, 12 May 2008 00:45:47 GMT"
}
]
| 2008-11-14T00:00:00 | [
[
"Wang",
"Zhi-Yong",
""
],
[
"Xiong",
"Cai-Dong",
""
]
]
|
quant-ph/0612091 | Pawel Maslanka | Katarzyna Bolonek, Piotr Kosinski | On the unitarity of higher-dervative and nonlocal theories | 8 pages, no figures | J.Phys.A40:11561-11568,2007 | 10.1088/1751-8113/40/38/008 | null | quant-ph hep-th | null | We consider two simple models of higher-derivative and nonlocal quantu
systems.It is shown that, contrary to some claims found in literature, they can
be made unitary.
| [
{
"version": "v1",
"created": "Tue, 12 Dec 2006 13:15:58 GMT"
}
]
| 2008-11-26T00:00:00 | [
[
"Bolonek",
"Katarzyna",
""
],
[
"Kosinski",
"Piotr",
""
]
]
|
quant-ph/0612092 | Marco Giovanni Genoni | Marco G. Genoni, Matteo G. A. Paris | Information/disturbance trade-off in single and sequential measurements
on a qudit signal | 7 pages, 4 figure. Proceedings of DICE06 (Piombino) | J. Phys. CP 67, 012029 (2007) | null | null | quant-ph | null | We address the trade-off between information gain and state disturbance in
measurement performed on qudit systems and devise a class of optimal
measurement schemes that saturate the ultimate bound imposed by quantum
mechanics to estimation and transmission fidelities. The schemes are minimal,
i.e. they involve a single additional probe qudit, and optimal, i.e. they
provide the maximum amount of information compatible with a given level of
disturbance. The performances of optimal single-user schemes in extracting
information by sequential measurements in a N -user transmission line are also
investigated, and the optimality is analyzed by explicit evaluation of
fidelities. We found that the estimation fidelity does not depend on the number
of users, neither for single-measure inference nor for collective one, whereas
the transmission fidelity decreases with N . The resulting trade-off is no
longer optimal and degrades with increasing N . We found that optimality can be
restored by an effective preparation of the probe states and present explicitly
calculations for the 2-user case.
| [
{
"version": "v1",
"created": "Tue, 12 Dec 2006 14:03:36 GMT"
}
]
| 2007-08-08T00:00:00 | [
[
"Genoni",
"Marco G.",
""
],
[
"Paris",
"Matteo G. A.",
""
]
]
|
quant-ph/0612093 | Quesne Christiane | C. Quesne, V.M. Tkachuk | Lorentz-covariant deformed algebra with minimal length | 8 pages, no figure, presented at XV International Colloquium on
Integrable Systems and Quantum Symmetries (ISQS-15), Prague, June 15-17, 2006 | Czech.J.Phys.56:1269-1274,2006 | 10.1007/s10582-006-0436-4 | ULB/229/CQ/06/5 | quant-ph hep-th math-ph math.MP | null | The $D$-dimensional two-parameter deformed algebra with minimal length
introduced by Kempf is generalized to a Lorentz-covariant algebra describing a
($D+1$)-dimensional quantized space-time. For D=3, it includes Snyder algebra
as a special case. The deformed Poincar\'e transformations leaving the algebra
invariant are identified. Uncertainty relations are studied. In the case of D=1
and one nonvanishing parameter, the bound-state energy spectrum and
wavefunctions of the Dirac oscillator are exactly obtained.
| [
{
"version": "v1",
"created": "Tue, 12 Dec 2006 15:01:53 GMT"
}
]
| 2008-11-26T00:00:00 | [
[
"Quesne",
"C.",
""
],
[
"Tkachuk",
"V. M.",
""
]
]
|
quant-ph/0612094 | Quesne Christiane | C. Quesne | More on an exactly solvable position-dependent mass Schroedinger
equation in two dimensions: Algebraic approach and extensions to three
dimensions | 23 pages, no figure | null | null | ULB/229/CQ/06/6 | quant-ph math-ph math.MP | null | An exactly solvable position-dependent mass Schr\"odinger equation in two
dimensions, depicting a particle moving in a semi-infinite layer, is
re-examined in the light of recent theories describing superintegrable
two-dimensional systems with integrals of motion that are quadratic functions
of the momenta. To get the energy spectrum a quadratic algebra approach is used
together with a realization in terms of deformed parafermionic oscillator
operators. In this process, the importance of supplementing algebraic
considerations with a proper treatment of boundary conditions for selecting
physical wavefunctions is stressed. Some new results for matrix elements are
derived. Finally, the two-dimensional model is extended to two integrable and
exactly solvable (but not superintegrable) models in three dimensions,
depicting a particle in a semi-infinite parallelepipedal or cylindrical
channel, respectively.
| [
{
"version": "v1",
"created": "Tue, 12 Dec 2006 15:08:08 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Quesne",
"C.",
""
]
]
|
quant-ph/0612095 | Jonas Larson | Jonas Larson | Dynamics of the Jayne-Cummings and Rabi models: old wine in new bottles | 16 pages, 17 figures; Replaced by published version; Accepted in
Physica Scripta | null | null | null | quant-ph cond-mat.other | null | By using a wave packet approach, this paper reviews the Jaynes-Cummings model
with and without the rotating wave approximation in a non-standard way. This
gives new insight, not only of the two models themselves, but of the rotating
wave approximation as well. Expressing the models by field quadrature
operators, instead of the typically used boson ladder operators, wave packet
simulations are presented. Several known phenomena of these systems, such as
collapse-revivals, Rabi oscillation, squeezing and entanglement, are reviewed
and explained in this new picture, either in an adiabatic or diabatic frame.
The harmonic shape of the potential curves that the wave packets evolve on and
the existence of a level crossing make these results interesting in a broader
sense than only for models in quantum optics, especially in atomic and
molecular physics.
| [
{
"version": "v1",
"created": "Tue, 12 Dec 2006 16:35:50 GMT"
},
{
"version": "v2",
"created": "Sat, 23 Jun 2007 18:42:36 GMT"
}
]
| 2007-06-23T00:00:00 | [
[
"Larson",
"Jonas",
""
]
]
|
quant-ph/0612096 | Robert A. Van Wesep | Robert A. Van Wesep | Compatibility of representations of quantum systems | The main theorem of this article is very basic, but I have been
unable to find any discussion of it or the issue it addresses in the existing
literature. As I do not wish to present this as new if it is not, I would
greatly appreciate any pertinent reference--even if only a published
statement that it is "well known" or "folklore" | null | null | null | quant-ph | null | There is a natural equivalence relation on representations of the states of a
given quantum system in a Hilbert space, two representations being equivalent
iff they are related by a unitary transformation. There are two equivalence
classes, with members of opposite classes being related by a conjugate-unitary
(anti-unitary) transformation. These two conjugacy classes are related in much
the same way as are the two imaginary units of a complex field, and there is a
priori no basis on which to prefer one over the other in any individual case.
This is potentially problematic in that the choice of conjugacy class of a
representation determines the sign of energy and other quantities defined as
generators of continuous symmetries of the system in question, so that it would
appear that principles like conservation of energy for a compound system may
hold or fail depending on relative choices of conjugacy class of
representations of its subsystems. We show that for any finite set of quantum
systems there are exactly two ways of choosing conjugacy classes of
representations consistent with the usual tensor-product construction for
representing the compound system composed of these. Each is obtained from the
other by reversing the conjugacy of all the representations at once. The
relation of unitary equivalence for representations of a single system is
therefore uniquely extendible to representations of all systems that can
interact with it.
| [
{
"version": "v1",
"created": "Tue, 12 Dec 2006 17:30:40 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Van Wesep",
"Robert A.",
""
]
]
|
quant-ph/0612097 | Casey Myers | Casey R. Myers, Marcus Silva, Kae Nemoto and William J. Munro | Stabilizer Quantum Error Correction with Qubus Computation | 4 pages, 5 figures | Phys. Rev. A 76, 012303 (2007) | 10.1103/PhysRevA.76.012303 | null | quant-ph | null | In this paper we investigate stabilizer quantum error correction codes using
controlled phase rotations of strong coherent probe states. We explicitly
describe two methods to measure the Pauli operators which generate the
stabilizer group of a quantum code. First, we show how to measure a Pauli
operator acting on physical qubits using a single coherent state with large
average photon number, displacement operations, and photon detection. Second,
we show how to measure the stabilizer operators fault-tolerantly by the
deterministic preparation of coherent cat states along with one-bit
teleportations between a qubit-like encoding of coherent states and physical
qubits.
| [
{
"version": "v1",
"created": "Tue, 12 Dec 2006 17:40:55 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Myers",
"Casey R.",
""
],
[
"Silva",
"Marcus",
""
],
[
"Nemoto",
"Kae",
""
],
[
"Munro",
"William J.",
""
]
]
|
quant-ph/0612098 | Giuseppe Florio | G. Costantini, P. Facchi, G. Florio, S. Pascazio | Multipartite entanglement characterization of a quantum phase transition | 10 pages, 6 figures, final version | J. Phys. A: Math. Theor. 40 (2007) 8009-8018 | 10.1088/1751-8113/40/28/S10 | null | quant-ph | null | A probability density characterization of multipartite entanglement is tested
on the one-dimensional quantum Ising model in a transverse field. The average
and second moment of the probability distribution are numerically shown to be
good indicators of the quantum phase transition. We comment on multipartite
entanglement generation at a quantum phase transition.
| [
{
"version": "v1",
"created": "Tue, 12 Dec 2006 19:07:43 GMT"
},
{
"version": "v2",
"created": "Thu, 28 Jun 2007 08:24:33 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Costantini",
"G.",
""
],
[
"Facchi",
"P.",
""
],
[
"Florio",
"G.",
""
],
[
"Pascazio",
"S.",
""
]
]
|
quant-ph/0612099 | Akira Kitagawa | Akira kitagawa, Masahiro Takeoka, Masahide Sasaki, and Anthony Chefles | Entanglement quantification with Fisher information | 4 pages, 4 figures | null | null | null | quant-ph | null | We show that the Fisher information associated with entanglement-assisted
coding has a monotonic relationship with the logarithmic negativity, an
important entanglement measure, for certain classes of continuous variable (CV)
quantum states of practical significance. These are the two-mode squeezed
states and the non-Gaussian states obtained from them by photon subtraction.
This monotonic correspondence can be expressed analytically in the case of pure
states. Numerical analysis shows that this relationship holds to a very good
approximation even in the mixed state case of the photon-subtracted squeezed
states. The Fisher information is evaluated by the CV Bell measurement in the
limit of weak signal modulation. Our results suggest that the logarithmic
negativity of certain sets of non-Gaussian mixed states can be experimentally
accessed without homodyne tomography, leading to significant simplification of
the experimental procedure.
| [
{
"version": "v1",
"created": "Wed, 13 Dec 2006 02:32:01 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"kitagawa",
"Akira",
""
],
[
"Takeoka",
"Masahiro",
""
],
[
"Sasaki",
"Masahide",
""
],
[
"Chefles",
"Anthony",
""
]
]
|
quant-ph/0612100 | John Jeffers | John Jeffers | Preamplified photodetectors for high-fidelity postselecting optical
devices | 5 pages, 7 figures, typos corrected and Journal Ref Added | Phys. Rev. A 75, 012335 (2007) | 10.1103/PhysRevA.75.012335 | null | quant-ph | null | The fidelity of postselecting devices based on direct photon number detection
can be significantly improved by insertion of a phase-insensitive optical
amplifier in front of the detector. The scheme is simple, and the cost to the
probability of obtaining the appropriate detector outcome is low.
| [
{
"version": "v1",
"created": "Wed, 13 Dec 2006 09:22:30 GMT"
},
{
"version": "v2",
"created": "Thu, 1 Feb 2007 11:20:54 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Jeffers",
"John",
""
]
]
|
quant-ph/0612101 | Klemens Hammerer | C. Schoen, K. Hammerer, M.M. Wolf, J.I. Cirac, E. Solano | Sequential Generation of Matrix-Product States in Cavity QED | 11 pages | Phys. Rev. A 75, 032311 (2007) | 10.1103/PhysRevA.75.032311 | null | quant-ph cond-mat.str-el | null | We study the sequential generation of entangled photonic and atomic
multi-qubit states in the realm of cavity QED. We extend the work of C. Schoen
et al. [Phys. Rev. Lett. 95, 110503 (2005)], where it was shown that all states
generated in a sequential manner can be classified efficiently in terms of
matrix-product states. In particular, we consider two scenarios: photonic
multi-qubit states sequentially generated at the cavity output of a
single-photon source and atomic multi-qubit states generated by their
sequential interaction with the same cavity mode.
| [
{
"version": "v1",
"created": "Wed, 13 Dec 2006 10:05:17 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Schoen",
"C.",
""
],
[
"Hammerer",
"K.",
""
],
[
"Wolf",
"M. M.",
""
],
[
"Cirac",
"J. I.",
""
],
[
"Solano",
"E.",
""
]
]
|
quant-ph/0612102 | Wang Zhi Yong | Zhi-Yong Wang, Cai-Dong Xiong | Theoretical evidence for the superluminality of evanescent modes | null | Physical Review A 75, 042105 (2007) | 10.1103/PhysRevA.75.042105 | null | quant-ph | null | Though both theoretical and experimental investigations have revealed the
superluminal behavior of evanescent electromagnetic waves, there are many
disputes about the physical meaning and validity of such superluminal
phenomenon, which is due to the fact that the traditional investigations are
based on the theory of tunneling time, and concerned with the problem of what
the group velocity of evanescent waves means. In this paper, by studying the
quantum probability amplitude for photons to propagate over a spacelike
interval along an undersized waveguide, we present theoretical evidence for
such superluminality.
| [
{
"version": "v1",
"created": "Wed, 13 Dec 2006 10:50:05 GMT"
},
{
"version": "v2",
"created": "Tue, 6 Mar 2007 15:29:56 GMT"
},
{
"version": "v3",
"created": "Sat, 24 Mar 2007 13:29:42 GMT"
},
{
"version": "v4",
"created": "Thu, 12 Apr 2007 01:59:14 GMT"
},
{
"version": "v5",
"created": "Sat, 18 Aug 2007 00:31:54 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Wang",
"Zhi-Yong",
""
],
[
"Xiong",
"Cai-Dong",
""
]
]
|
quant-ph/0612103 | Helena Granstrom | Helena Granstrom | Some remarks on the theorems of Gleason and Kochen-Specker | null | null | null | null | quant-ph | null | A Gleason-type theorem is proved for two restricted classes of
informationally complete POVMs in the qubit case. A particular (incomplete)
Kochen-Specker colouring, suggested by Appleby in dimension three, is
generalized to arbitrary dimension. We investigate its effectivity as a
function of dimension, using two different measures of this. In particular, we
will derive a limit for the fraction of the sphere that can be satisfactorily
coloured using the generalized Appleby construction as the number of dimensions
approaches infinity. The second, and physically more relevant measure of
effectivity, is to look at the fraction of possible ON-bases properly coloured.
Using this measure, we will derive a 'lower bound for the upper bound' in three
and four real dimensions.
| [
{
"version": "v1",
"created": "Wed, 13 Dec 2006 11:45:21 GMT"
},
{
"version": "v2",
"created": "Mon, 3 Sep 2007 08:12:20 GMT"
}
]
| 2007-09-03T00:00:00 | [
[
"Granstrom",
"Helena",
""
]
]
|
quant-ph/0612104 | Mikhail Fedorov V. | M.V. Fedorov, M.A. Efremov, P.A. Volkov, E.V. Moreva, S.S. Straupe,
and S.P. Kulik | Anisotropically high entanglement of biphotons generated in spontaneous
parametric down conversion | null | null | 10.1103/PhysRevLett.99.063901 | null | quant-ph | null | We show that the wave packet of a biphoton generated via spontaneous
parametric down conversion is strongly anisotropic. Its anisotropic features
manifest themselves very clearly in comparison of measurements performed in two
different schemes: when the detector scanning plane is perpendicular or
parallel to the plane containing the crystal optical axis and the laser axis.
The first of these two schemes is traditional whereas the second one gives rise
to such unexpected new results as anomalously strong narrowing of the biphoton
wave packet measured in the coincidence scheme and very high degree of
entanglement. The results are predicted theoretically and confirmed
experimentally.
| [
{
"version": "v1",
"created": "Wed, 13 Dec 2006 16:03:25 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Fedorov",
"M. V.",
""
],
[
"Efremov",
"M. A.",
""
],
[
"Volkov",
"P. A.",
""
],
[
"Moreva",
"E. V.",
""
],
[
"Straupe",
"S. S.",
""
],
[
"Kulik",
"S. P.",
""
]
]
|
quant-ph/0612105 | P. G. L. Porta Mana | A. M{\aa}nsson, P. G. L. Porta Mana, G. Bj\"ork | Numerical Bayesian state assignment for a three-level quantum system. I.
Absolute-frequency data; constant and Gaussian-like priors | 23 pages, 14 figures. V2: Added an important note concerning
cylindrical algebraic decomposition and thanks to P B Slater, corrected some
typos, added references | null | null | null | quant-ph | null | This paper offers examples of concrete numerical applications of Bayesian
quantum-state-assignment methods to a three-level quantum system. The
statistical operator assigned on the evidence of various measurement data and
kinds of prior knowledge is computed partly analytically, partly through
numerical integration (in eight dimensions) on a computer. The measurement data
consist in absolute frequencies of the outcomes of N identical von Neumann
projective measurements performed on N identically prepared three-level
systems. Various small values of N as well as the large-N limit are considered.
Two kinds of prior knowledge are used: one represented by a plausibility
distribution constant in respect of the convex structure of the set of
statistical operators; the other represented by a Gaussian-like distribution
centred on a pure statistical operator, and thus reflecting a situation in
which one has useful prior knowledge about the likely preparation of the
system.
In a companion paper the case of measurement data consisting in average
values, and an additional prior studied by Slater, are considered.
| [
{
"version": "v1",
"created": "Wed, 13 Dec 2006 17:05:27 GMT"
},
{
"version": "v2",
"created": "Sun, 29 Apr 2007 16:22:50 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Månsson",
"A.",
""
],
[
"Mana",
"P. G. L. Porta",
""
],
[
"Björk",
"G.",
""
]
]
|
quant-ph/0612106 | Christof Wunderlich | N. Timoney, V. Elman, W. Neuhauser, Chr. Wunderlich | Error-resistant Single Qubit Gates with Trapped Ions | 5 pages 5 figures | Physical Review A 77, 052334 (2008) | 10.1103/PhysRevA.77.052334 | null | quant-ph | null | Coherent operations constitutive for the implementation of single and
multi-qubit quantum gates with trapped ions are demonstrated that are robust
against variations in experimental parameters and intrinsically indeterministic
system parameters. In particular, pulses developed using optimal control theory
are demonstrated for the first time with trapped ions. Their performance as a
function of error parameters is systematically investigated and compared to
composite pulses.
| [
{
"version": "v1",
"created": "Wed, 13 Dec 2006 17:56:21 GMT"
}
]
| 2011-12-23T00:00:00 | [
[
"Timoney",
"N.",
""
],
[
"Elman",
"V.",
""
],
[
"Neuhauser",
"W.",
""
],
[
"Wunderlich",
"Chr.",
""
]
]
|
quant-ph/0612107 | Dave Bacon | Dave Bacon | How a Clebsch-Gordan Transform Helps to Solve the Heisenberg Hidden
Subgroup Problem | 30 pages, uses qic.sty | null | null | null | quant-ph cs.CC | null | It has recently been shown that quantum computers can efficiently solve the
Heisenberg hidden subgroup problem, a problem whose classical query complexity
is exponential. This quantum algorithm was discovered within the framework of
using pretty-good measurements for obtaining optimal measurements in the hidden
subgroup problem. Here we show how to solve the Heisenberg hidden subgroup
problem using arguments based instead on the symmetry of certain hidden
subgroup states. The symmetry we consider leads naturally to a unitary
transform known as the Clebsch-Gordan transform over the Heisenberg group. This
gives a new representation theoretic explanation for the pretty-good
measurement derived algorithm for efficiently solving the Heisenberg hidden
subgroup problem and provides evidence that Clebsch-Gordan transforms over
finite groups are a new primitive in quantum algorithm design.
| [
{
"version": "v1",
"created": "Wed, 13 Dec 2006 18:37:08 GMT"
},
{
"version": "v2",
"created": "Thu, 20 Sep 2007 17:08:30 GMT"
}
]
| 2007-09-20T00:00:00 | [
[
"Bacon",
"Dave",
""
]
]
|
quant-ph/0612108 | Otfried Guehne | Otfried G\"uhne, Norbert L\"utkenhaus | Nonlinear entanglement witnesses, covariance matrices and the geometry
of separable states | 12 pages, 2 figures, for the proceedings of DICE2006 in Piombino
(Italy) | J. Phys.: Conf. Ser. 67, 012004 (2007) | 10.1088/1742-6596/67/1/012004 | null | quant-ph | null | Entanglement witnesses provide a standard tool for the analysis of
entanglement in experiments. We investigate possible nonlinear entanglement
witnesses from several perspectives. First, we demonstrate that they can be
used to show that the set of separable states has no facets. Second, we give a
new derivation of nonlinear witnesses based on covariance matrices. Finally, we
investigate extensions to the multipartite case.
| [
{
"version": "v1",
"created": "Wed, 13 Dec 2006 19:17:01 GMT"
}
]
| 2007-06-13T00:00:00 | [
[
"Gühne",
"Otfried",
""
],
[
"Lütkenhaus",
"Norbert",
""
]
]
|
quant-ph/0612109 | Johan Wulleman | Johan Wulleman | About the Exact Role of Disturbance in Heisenberg's Uncertainty Relation | 26 pages, 3 figures; available from http://www.physicsessays.com .
This paper goes together with another paper: J.Wulleman, Concepts of Physics
3, 211 (2006), available from
http://merlin.fic.uni.lodz.pl/concepts/index.htm | Physics Essays 16 (2003) 413-427 | null | null | quant-ph | null | It is generally accepted that the disturbance interpretation cannot explain
Heisenberg's uncertainty relation DxDp=h. In this paper a clear distinction
will be made between the notions of state preparation and measurement, noting
that the disturbance that is referred to in Heisenberg's disturbance
interpretation is usually caused by the measurement. The main goal of this
paper is to examine and discuss to what extent disturbance during the state
preparation plays a role in the interpretation of Heisenberg's uncertainty
relation. This examination will be done in the context of a single-slit
experiment. To conclude this paper a novel single-slit experiment will be
proposed and discussed with which a clearer insight could be gained into the
exact role of disturbance when a quantum system passes a single-slit.
| [
{
"version": "v1",
"created": "Wed, 13 Dec 2006 20:55:38 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Wulleman",
"Johan",
""
]
]
|
quant-ph/0612110 | Kirill A. Kazakov | Kirill A. Kazakov | Quantum fluctuations of Coulomb Potential as a Source of Flicker Noise.
The Influence of Heat Bath | 15 pages, 3 figures. The published version | J. Phys. A: Math. Theor. 40 (2007) 5277-5296 | 10.1088/1751-8113/40/20/004 | null | quant-ph | null | The power spectrum of finite-temperature quantum electromagnetic fluctuations
produced by elementary charge carriers under the influence of external electric
field is investigated. It is found that under the combined action of the photon
heat bath and the external field, the low-frequency asymptotic of the power
spectrum is modified both qualitatively and quantitatively. The new term in the
power spectrum is inversely proportional to, but is odd in frequency. It comes
from the connected part of the correlation function, and is related to the
temperature and external field corrections to the photon and charge carrier
propagators. In application to the case of a biased conducting sample, this
term gives rise to a contribution to the voltage power spectrum which is
proportional to the absolute system temperature, the charge carrier mobility,
the bias voltage squared, and a factor describing dependence of the noise
intensity on the sample geometry. It is verified that the derived expression is
in agreement with the experimental data on 1/f-noise measurements in metal
films.
| [
{
"version": "v1",
"created": "Wed, 13 Dec 2006 22:41:42 GMT"
},
{
"version": "v2",
"created": "Tue, 15 May 2007 18:17:26 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Kazakov",
"Kirill A.",
""
]
]
|
quant-ph/0612111 | Ling Zhou | Gao Wen Bin, Yang Guo Hui and Zhou Ling | Multi-impurity effects on the entanglement of anisotropic Heisenberg
ring XXZ under a homogeneous magnetic field | 4 pages, 6 figures | null | null | null | quant-ph | null | The effects of multi-impurity on the entanglement of anisotropic Heisenberg
ring XXZ under a homogeneous magnetic field have been studied. The impurities
make the equal pairwise entanglement in a ring compete with each other so that
the pairwise entanglement exhibits oscillation. If the impurities are of larger
couplings, both the critical temperature and pairwise entanglement can be
improved
| [
{
"version": "v1",
"created": "Thu, 14 Dec 2006 02:11:49 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Bin",
"Gao Wen",
""
],
[
"Hui",
"Yang Guo",
""
],
[
"Ling",
"Zhou",
""
]
]
|
quant-ph/0612112 | Marco Fiorentino | M. Fiorentino, C. M. Santori, S. M. Spillane, W. J. Munro, R. G.
Beausoleil | Secure self-calibrating quantum random bit generator | 5 pages, 2 figures | Phys. Rev. A 75, 032334 (2007) | 10.1103/PhysRevA.75.032334 | null | quant-ph | null | Random bit generators (RBGs) are key components of a variety of information
processing applications ranging from simulations to cryptography. In
particular, cryptographic systems require "strong" RBGs that produce
high-entropy bit sequences, but traditional software pseudo-RBGs have very low
entropy content and therefore are relatively weak for cryptography. Hardware
RBGs yield entropy from chaotic or quantum physical systems and therefore are
expected to exhibit high entropy, but in current implementations their exact
entropy content is unknown. Here we report a quantum random bit generator
(QRBG) that harvests entropy by measuring single-photon and entangled
two-photon polarization states. We introduce and implement a quantum
tomographic method to measure a lower bound on the "min-entropy" of the system,
and we employ this value to distill a truly random bit sequence. This approach
is secure: even if an attacker takes control of the source of optical states, a
secure random sequence can be distilled.
| [
{
"version": "v1",
"created": "Thu, 14 Dec 2006 01:39:30 GMT"
},
{
"version": "v2",
"created": "Fri, 30 Mar 2007 17:41:46 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Fiorentino",
"M.",
""
],
[
"Santori",
"C. M.",
""
],
[
"Spillane",
"S. M.",
""
],
[
"Munro",
"W. J.",
""
],
[
"Beausoleil",
"R. G.",
""
]
]
|
quant-ph/0612113 | Daniel Nagaj | Daniel Nagaj, Shay Mozes | A new construction for a QMA complete 3-local Hamiltonian | 11 pages, 4 figures | J. Math. Phys. 48, 072104 (2007) | 10.1063/1.2748377 | null | quant-ph | null | We present a new way of encoding a quantum computation into a 3-local
Hamiltonian. Our construction is novel in that it does not include any terms
that induce legal-illegal clock transitions. Therefore, the weights of the
terms in the Hamiltonian do not scale with the size of the problem as in
previous constructions. This improves the construction by Kempe and Regev, who
were the first to prove that 3-local Hamiltonian is complete for the complexity
class QMA, the quantum analogue of NP.
Quantum k-SAT, a restricted version of the local Hamiltonian problem using
only projector terms, was introduced by Bravyi as an analogue of the classical
k-SAT problem. Bravyi proved that quantum 4-SAT is complete for the class QMA
with one-sided error (QMA_1) and that quantum 2-SAT is in P. We give an
encoding of a quantum circuit into a quantum 4-SAT Hamiltonian using only
3-local terms. As an intermediate step to this 3-local construction, we show
that quantum 3-SAT for particles with dimensions 3x2x2 (a qutrit and two
qubits) is QMA_1 complete. The complexity of quantum 3-SAT with qubits remains
an open question.
| [
{
"version": "v1",
"created": "Thu, 14 Dec 2006 18:47:10 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Nagaj",
"Daniel",
""
],
[
"Mozes",
"Shay",
""
]
]
|
quant-ph/0612114 | Fei Gao | Fei Gao, Su-Juan Qin, Qiao-Yan Wen, Fu-Chen Zhu | Fake one-time pad cannot be used to improve the efficiency of quantum
communication | 6 pages, no figures | null | 10.1016/j.physleta.2007.01.047 | null | quant-ph | null | Two misuses of one-time pad in improving the efficiency of quantum
communication are pointed out. One happens when using some message bits to
encrypt others, the other exists because the key bits are not truly random.
Both of them result in the decrease of security. Therefore, one-time pad should
be used carefully in designing quantum communication protocols.
| [
{
"version": "v1",
"created": "Thu, 14 Dec 2006 06:38:28 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Gao",
"Fei",
""
],
[
"Qin",
"Su-Juan",
""
],
[
"Wen",
"Qiao-Yan",
""
],
[
"Zhu",
"Fu-Chen",
""
]
]
|
quant-ph/0612115 | Jun Jing | Jun Jing and Zhi-Guo L\"u | Quantum dynamics of double-qubits in a spin star lattice with an XY
interaction | 16 pages, 8 figures, submitted to JPA | null | null | null | quant-ph | null | The dynamics of two coupled spins-1/2 interacting with a spin-bath via the
quantum Heisenberg XY coupling is studied. The pair of central spins served as
a quantum open subsystem are initially prepared in two types of states: the
product states and the Bell states. The bath, which consists of $N$ (in the
thermodynamic limit $N\to\infty$) mutually coupled spins-1/2, is in a thermal
state at the beginning. By the Holstein-Primakoff transformation, the model can
be treated effectively as two spin qubits embedded in a single mode cavity. The
time-evolution of the purity, z-component summation and the concurrence of the
central spins can be determined by a Laguerre polynomial scheme. It is found
that (i) at a low temperature, the uncoupled subsystem in a product state can
be entangled due to the interaction with bath, which is tested by the
Peres-Horodecki separability; however, at a high temperature, the bath produces
a stronger destroy effect on the purity and entanglement of the subsystem; (ii)
when the coupling strength between the two central spins is large, they are
protected strongly against the bath; (iii) when the interaction between the
subsystem and the bath is strong, the collapse of the two spin qubits from
their initial entangled state is fast.
| [
{
"version": "v1",
"created": "Thu, 14 Dec 2006 07:24:12 GMT"
},
{
"version": "v2",
"created": "Tue, 9 Oct 2007 13:56:01 GMT"
}
]
| 2007-10-09T00:00:00 | [
[
"Jing",
"Jun",
""
],
[
"Lü",
"Zhi-Guo",
""
]
]
|
quant-ph/0612116 | Curceanu Catalina | S. Bartalucci, S. Bertolucci, M. Bragadireanu, M. Cargnelli, M.
Catitti, C. Curceanu (Petrascu), S. Di Matteo, J.-P. Egger, C. Guaraldo, M.
Iliescu, T. Ishiwatari, M. Laubenstein, J. Marton, E. Milotti, D. Pietreanu,
T. Ponta, D.L. Sirghi, F. Sirghi, L. Sperandio, O. Vazquez Doce, E. Widmann,
J. Zmeskal | New experimental limit on Pauli Exclusion Principle violation by
electrons (the VIP experiment) | submitted to Journal of Physics: Conference Series, by the Institute
of Physics | null | 10.1088/1742-6596/67/1/012033 | null | quant-ph | null | The Pauli exclusion principle (PEP) represents one of the basic principles of
modern physics and, even if there are no compelling reasons to doubt its
validity, it still spurs a lively debate, because an intuitive, elementary
explanation is still missing, and because of its unique stand among the basic
symmetries of physics. A new limit on the probability that PEP is violated by
electrons was estabilished by the VIP (VIolation of the Pauli exclusion
principle) Collaboration, using the method of searching for PEP forbidden
atomic transitions in copper. The preliminary value, ${1/2}\beta^{2} \textless
4.5\times 10^{-28}$, represents an improvement of about two orders of magnitude
of the previous limit. The goal of VIP is to push this limit at the level of
$10^{-30}$.
| [
{
"version": "v1",
"created": "Thu, 14 Dec 2006 11:21:53 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Bartalucci",
"S.",
"",
"Petrascu"
],
[
"Bertolucci",
"S.",
"",
"Petrascu"
],
[
"Bragadireanu",
"M.",
"",
"Petrascu"
],
[
"Cargnelli",
"M.",
"",
"Petrascu"
],
[
"Catitti",
"M.",
"",
"Petrascu"
],
[
"Curceanu",
"C.",
"",
"Petrascu"
],
[
"Di Matteo",
"S.",
""
],
[
"Egger",
"J. -P.",
""
],
[
"Guaraldo",
"C.",
""
],
[
"Iliescu",
"M.",
""
],
[
"Ishiwatari",
"T.",
""
],
[
"Laubenstein",
"M.",
""
],
[
"Marton",
"J.",
""
],
[
"Milotti",
"E.",
""
],
[
"Pietreanu",
"D.",
""
],
[
"Ponta",
"T.",
""
],
[
"Sirghi",
"D. L.",
""
],
[
"Sirghi",
"F.",
""
],
[
"Sperandio",
"L.",
""
],
[
"Doce",
"O. Vazquez",
""
],
[
"Widmann",
"E.",
""
],
[
"Zmeskal",
"J.",
""
]
]
|
quant-ph/0612117 | Dorje C. Brody | Dorje C. Brody, Anna C. T. Gustavsson, Lane P. Hughston | Entanglement of three-qubit geometry | 6 pages, 4 figures. Based on the talk presented at DICE 2006 | Journal of Physics: Conf. Ser. 67 (2007) 012044 | 10.1088/1742-6596/67/1/012044 | null | quant-ph | null | Geometric quantum mechanics aims to express the physical properties of
quantum systems in terms of geometrical features preferentially selected in the
space of pure states. Geometric characterisations are given here for systems of
one, two, and three spin-1/2 particles, drawing attention to the classification
of quantum states into entanglement types.
| [
{
"version": "v1",
"created": "Thu, 14 Dec 2006 11:45:24 GMT"
}
]
| 2007-06-13T00:00:00 | [
[
"Brody",
"Dorje C.",
""
],
[
"Gustavsson",
"Anna C. T.",
""
],
[
"Hughston",
"Lane P.",
""
]
]
|
quant-ph/0612118 | Klaus Hornberger | Klaus Hornberger | Introduction to decoherence theory | 57 pages, 2 figures; some new material added and typos corrected.
This corresponds to the published version | K. Hornberger, Lect. Notes Phys. 768, 221-276 (2009) | 10.1007/978-3-540-88169-8_5 | null | quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is an introduction to the theory of decoherence with an emphasis on its
microscopic origins and on a dynamic description. The text corresponds to a
chapter soon to be published in: A. Buchleitner, C. Viviescas, and M. Tiersch
(Eds.), Entanglement and Decoherence. Foundations and Modern Trends, Lecture
Notes in Physics, Vol 768, Springer, Berlin (2009)
| [
{
"version": "v1",
"created": "Thu, 14 Dec 2006 14:16:39 GMT"
},
{
"version": "v2",
"created": "Thu, 22 Feb 2007 18:04:07 GMT"
},
{
"version": "v3",
"created": "Wed, 5 Nov 2008 22:41:13 GMT"
}
]
| 2008-11-13T00:00:00 | [
[
"Hornberger",
"Klaus",
""
]
]
|
quant-ph/0612119 | Jaromir Fiurasek | Lucie Bartuskova, Miloslav Dusek, Antonin Cernoch, Jan Soubusta,
Jaromir Fiurasek | Fibre-optics implementation of asymmetric phase-covariant quantum cloner | 4 pages, 3 figures, RevTeX4 | Phys. Rev. Lett. 99, 120505 (2007). | 10.1103/PhysRevLett.99.120505 | null | quant-ph | null | We present the experimental realization of optimal symmetric and asymmetric
phase-covariant 1->2 cloning of qubit states using fiber optics. State of each
qubit is encoded into a single photon which can propagate through two optical
fibers. The operation of our device is based on one- and two-photon
interference. We have demonstrated creation of two copies of any state of a
qubit from the equator of the Bloch sphere. The measured fidelities of both
copies are close to the theoretical values and they surpass the theoretical
maximum obtainable with the universal cloner.
| [
{
"version": "v1",
"created": "Thu, 14 Dec 2006 14:33:06 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Bartuskova",
"Lucie",
""
],
[
"Dusek",
"Miloslav",
""
],
[
"Cernoch",
"Antonin",
""
],
[
"Soubusta",
"Jan",
""
],
[
"Fiurasek",
"Jaromir",
""
]
]
|
quant-ph/0612120 | Dorje C. Brody | Dorje C. Brody, Daniel W. Hook, Lane P. Hughston | On quantum microcanonical equilibrium | 6 pages, 3 figures. To appear in DICE 2006 conference proceedings | Journal of Physics: Conf. Ser. 67 (2007) 012025 | 10.1088/1742-6596/67/1/012025 | null | quant-ph | null | A quantum microcanonical postulate is proposed as a basis for the equilibrium
properties of small quantum systems. Expressions for the corresponding density
of states are derived, and are used to establish the existence of phase
transitions for finite quantum systems. A grand microcanonical ensemble is
introduced, which can be used to obtain new rigorous results in quantum
statistical mechanics.
| [
{
"version": "v1",
"created": "Thu, 14 Dec 2006 15:19:40 GMT"
}
]
| 2007-06-13T00:00:00 | [
[
"Brody",
"Dorje C.",
""
],
[
"Hook",
"Daniel W.",
""
],
[
"Hughston",
"Lane P.",
""
]
]
|
quant-ph/0612121 | ChengZhi Peng | Xiang-Bin Wang, Cheng-Zhi Peng, Jun Zhang, Jian-Wei Pan | Security of decoy-state quantum key distribution with inexactly
controlled source | null | null | 10.1103/PhysRevA.77.042311 | null | quant-ph | null | We show the unconditional security of decoy-state method quantum cryptography
with whatever intensity error pattern provided that the error is not too large.
Our result immediately applies to the existing experimental data. Our result is
not limitted to coherent states.
| [
{
"version": "v1",
"created": "Thu, 14 Dec 2006 16:24:19 GMT"
},
{
"version": "v2",
"created": "Mon, 12 Mar 2007 16:29:45 GMT"
},
{
"version": "v3",
"created": "Fri, 8 Feb 2008 08:41:15 GMT"
}
]
| 2013-05-29T00:00:00 | [
[
"Wang",
"Xiang-Bin",
""
],
[
"Peng",
"Cheng-Zhi",
""
],
[
"Zhang",
"Jun",
""
],
[
"Pan",
"Jian-Wei",
""
]
]
|
quant-ph/0612122 | Alexandre Gavrilik | A.M. Gavrilik, A.P. Rebesh | A q-Oscillator with 'Accidental' Degeneracy of Energy Levels | 12 pages, 7 figures; v.2 misprints corrected, two references added,
to appear in Mod.Phys.Lett.A | Mod.Phys.Lett.A22:949-960,2007 | 10.1142/S0217732307022827 | null | quant-ph cond-mat.stat-mech hep-th math-ph math.MP nucl-th | null | We study main features of the exotic case of q-deformed oscillators
(so-called Tamm-Dancoff cutoff oscillator) and find some special properties:
(i) degeneracy of the energy levels E_{n_1} = E_{n_1+1}, n_1\ge 1, at the {\em
real value} q=\sqrt{\frac{n_1}{n_1+2}} of deformation parameter, as well as the
occurrence of other degeneracies E_{n_1} = E_{n_1+k}, for k \ge 2, at the
corresponding values of q which depend on both n_1 and k; (ii) the position and
momentum operators X and P {\em commute on the state} |m> if q is fixed as
q=\frac{m}{m+1}, that implies unusual uncertainty relation; (iii) two commuting
copies of the creation, annihilation, and number operators of this q-oscillator
generate the corresponding q-deformation of the {\em non-simple} Lie algebra
su(2)\oplus u(1) whose nontrivial q-deformed commutation relation is: [ J_+,
J_- ] = 2 J_0 q^{2J_3-1} where J_0\equiv \frac12 (N_1-N_2) and J_3\equiv
\frac12 (N_1+N_2).
| [
{
"version": "v1",
"created": "Thu, 14 Dec 2006 19:36:14 GMT"
},
{
"version": "v2",
"created": "Thu, 8 Feb 2007 20:19:23 GMT"
}
]
| 2008-11-26T00:00:00 | [
[
"Gavrilik",
"A. M.",
""
],
[
"Rebesh",
"A. P.",
""
]
]
|
quant-ph/0612123 | Indranil Chakrabarty ic | Indranil Chakrabarty | Impossibility of partial swapping of Quantum Information | Accepted for publication in IJQI | IJQI,Volume: 5 No: 4 Year: 2007 pp. 605-609 | null | null | quant-ph | null | It is a well known fact that a quantum state $|\psi(\theta,\phi)>$ are
represented by a point on the Bloch sphere, characterized by two parameters
$\theta$ and $\phi$. Here in this work, we find out another impossible
operation in quantum information theory . We name this impossibility as
'Impossibility of partial swapping of quantum information '. By this we mean
that if two unknown quantum states are given at the input port, there exists no
physical process, consistent with the principles of quantum mechanics, by which
we can partially swap either of the two parameters $\theta$ and $\phi$ between
these two quantum states. In this work we provided the impossibility proofs for
the qubits(i.e the quantum states taken from two dimensional Hilbert space) and
this impossible operation can be shown to hold in higher dimension also.
| [
{
"version": "v1",
"created": "Thu, 14 Dec 2006 18:53:13 GMT"
},
{
"version": "v2",
"created": "Wed, 6 Jun 2007 15:59:33 GMT"
}
]
| 2011-11-09T00:00:00 | [
[
"Chakrabarty",
"Indranil",
""
]
]
|
quant-ph/0612124 | Alex Hayat | Alex Hayat, Pavel Ginzburg, and Meir Orenstein | High-Rate Entanglement Source via Two-Photon Emission from Semiconductor
Quantum Wells | null | null | 10.1103/PhysRevB.76.035339 | null | quant-ph | null | We propose a compact high-intensity room-temperature source of entangled
photons based on the efficient second-order process of two-photon spontaneous
emission from electrically-pumped semiconductor quantum wells in a photonic
microcavity. Two-photon emission rate in room-temperature semiconductor devices
is determined solely by the carrier density, regardless of the residual
one-photon emission. The microcavity selects two-photon emission for a specific
signal and idler wavelengths and at a preferred direction without modifying the
overall rate. Pair-generation rate in GaAs/AlGaAs quantum well structure is
estimated using a 14-band model to be 3 orders of magnitude higher than for
traditional broadband parametric down-conversion sources.
| [
{
"version": "v1",
"created": "Thu, 14 Dec 2006 20:32:50 GMT"
},
{
"version": "v2",
"created": "Thu, 17 May 2007 14:30:09 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Hayat",
"Alex",
""
],
[
"Ginzburg",
"Pavel",
""
],
[
"Orenstein",
"Meir",
""
]
]
|
quant-ph/0612125 | Carmen Tornow | Carmen Tornow | Intrinsic Regularization in a Lorentz invariant non-orthogonal Euclidean
Space | 11 pages, 3 figures | null | null | null | quant-ph | null | It is shown that the Lorentz transformations can be derived for a
non-orthogonal Euclidean space. In this geometry one finds the same relations
of special relativity as the ones known from the orthogonal Minkowski space. In
order to illustrate the advantage of a non-orthogonal Euclidean metric the
two-point Green's function at x = 0 for a self-interacting scalar field is
calculated. In contrast to the Minkowski space the one loop mass correction
derived from this function gives a convergent result due to an intrinsic
regularization parameter called effective dimension. This parameter is an
entropy related measure for the information loss caused by quantum fluctuations
of the metric at energies higher than the Planckian limit.
| [
{
"version": "v1",
"created": "Fri, 15 Dec 2006 20:58:32 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Tornow",
"Carmen",
""
]
]
|
quant-ph/0612126 | David Poulin | David Poulin and Jon Yard | Dynamics of a Quantum Reference Frame | null | New J. Phys 9, 156 (2007) | 10.1088/1367-2630/9/5/156 | null | quant-ph | null | We analyze a quantum mechanical gyroscope which is modeled as a large spin
and used as a reference against which to measure the angular momenta of
spin-1/2 particles. These measurements induce a back-action on the reference
which is the central focus of our study. We begin by deriving explicit
expressions for the quantum channel representing the back-action. Then, we
analyze the dynamics incurred by the reference when it is used to sequentially
measure particles drawn from a fixed ensemble. We prove that the reference
thermalizes with the measured particles and find that generically, the thermal
state is reached in time which scales linearly with the size of the reference.
This contrasts a recent conclusion of Bartlett et al. that this takes a
quadratic amount of time when the particles are completely unpolarized. We now
understand their result in terms of a simple physical principle based on
symmetries and conservation laws. Finally, we initiate the study of the
non-equilibrium dynamics of the reference. Here we find that a reference in a
coherent state will essentially remain in one when measuring polarized
particles, while rotating itself to ultimately align with the polarization of
the particles.
| [
{
"version": "v1",
"created": "Fri, 15 Dec 2006 01:33:27 GMT"
},
{
"version": "v2",
"created": "Wed, 30 May 2007 18:48:09 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Poulin",
"David",
""
],
[
"Yard",
"Jon",
""
]
]
|
quant-ph/0612127 | Ou Yong-Cheng | Yong-Cheng Ou | Violation of monogamy inequality for higher-dimensional objects | 2.5 pages,minor modifications are made | 75, 034305(2007) Physical Review A | 10.1103/PhysRevA.75.034305 | null | quant-ph | null | Bipartite quantum entanglement for qutrits and higher-dimensional objects is
considered. We analyze the possibility of violation of monogamy inequality,
introduced by Coffman, Kundu, and Wootters, for some systems composed of such
objects. An explicit counterexample with a three-qutrit totally antisymmetric
state is presented. Since three-tangle has been confirmed to be a natural
measure of entanglement for qubit systems, our result shows that the
three-tangle is no longer a legitimate measure of entanglement for states with
three qutrits or higher dimensional objects.
| [
{
"version": "v1",
"created": "Fri, 15 Dec 2006 04:19:23 GMT"
},
{
"version": "v2",
"created": "Thu, 1 Mar 2007 07:18:07 GMT"
},
{
"version": "v3",
"created": "Tue, 27 Mar 2007 05:20:46 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Ou",
"Yong-Cheng",
""
]
]
|
quant-ph/0612128 | Zhangqi Yin | Peng Peng, Fu-li Li | Entangling two atoms in spatially separated cavities through both photon
emission and absorption processes | 12 pages, 4 figures | Phys. Rev. A 75, 062320 (2007) | 10.1103/PhysRevA.75.062320 | null | quant-ph | null | We consider a system consisting of a $\Lambda$-type atom and a V-type atom,
which are individually trapped in two spatially separated cavities that are
connected by an optical fibre. We show that an extremely entangled state of the
two atoms can be deterministically generated through both photon emission of
the $\Lambda$-type atom and photon absorption of the V-type atom in an ideal
situation. The influence of various decoherence processes such as spontaneous
emission and photon loss on the fidelity of the entangled state is also
investigated. We find that the effect of photon leakage out of the fibre on the
fidelity can be greatly diminished in some special cases. As regards the effect
of spontaneous emission and photon loss from the cavities, we find that the
present scheme with a fidelity higher than 0.98 may be realized under current
experiment conditions.
| [
{
"version": "v1",
"created": "Fri, 15 Dec 2006 09:54:06 GMT"
},
{
"version": "v2",
"created": "Fri, 29 Dec 2006 13:54:45 GMT"
}
]
| 2007-06-20T00:00:00 | [
[
"Peng",
"Peng",
""
],
[
"Li",
"Fu-li",
""
]
]
|
quant-ph/0612129 | Anne Ersbak Bang Nielsen | Anne E. B. Nielsen and Klaus Molmer | Photon number states generated from a continuous-wave light source | 8 pages, 7 figures, v2: shortened version | Phys. Rev. A 75, 043801 (2007) | 10.1103/PhysRevA.75.043801 | null | quant-ph | null | Conditional preparation of photon number states from a continuous-wave
nondegenerate optical parametric oscillator is investigated. We derive the
phase space Wigner function for the output state conditioned on photo detection
events that are not necessarily simultaneous, and we maximize its overlap with
the desired photon number state by choosing the optimal temporal output state
mode function. We present a detailed numerical analysis for the case of
two-photon state generation from a parametric oscillator driven with an
arbitrary intensity below threshold, and in the low intensity limit, we present
a formalism that yields the optimal output state mode function and fidelity for
higher photon number states.
| [
{
"version": "v1",
"created": "Fri, 15 Dec 2006 11:09:36 GMT"
},
{
"version": "v2",
"created": "Fri, 20 Apr 2007 16:51:44 GMT"
}
]
| 2007-06-07T00:00:00 | [
[
"Nielsen",
"Anne E. B.",
""
],
[
"Molmer",
"Klaus",
""
]
]
|
quant-ph/0612130 | Robert Collins | Veronica Fernandez, Robert J. Collins, Karen J. Gordon, Paul D.
Townsend, and Gerald S. Buller | Passive Optical Network Approach to GigaHertz-Clocked Multiuser Quantum
Key Distribution | 9 pages, PDF only | IEEE Journal of Quantum Electronics, Volume 43 (2), (2007) | 10.1109/JQE.2006.887175 | null | quant-ph | null | We present the application of quantum key distribution technologies to
fiber-based broadband passive optical access networks. This application is
based on our 850 nm wavelength gigahertz clock-rate single-receiver system, is
compatible with existing telecommunications fiber and exploits a wavelength
band not currently utilized in access networks. The developed quantum key
distribution networks are capable of transmitting over distances consistent
with the span of access links for metropolitan networks (10 km), at clock
frequencies ranging up to 3 GHz.
| [
{
"version": "v1",
"created": "Fri, 15 Dec 2006 12:15:31 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Fernandez",
"Veronica",
""
],
[
"Collins",
"Robert J.",
""
],
[
"Gordon",
"Karen J.",
""
],
[
"Townsend",
"Paul D.",
""
],
[
"Buller",
"Gerald S.",
""
]
]
|
quant-ph/0612131 | Pawel Caban | Pawel Caban, Jakub Rembielinski | Einstein-Podolsky-Rosen correlations of Dirac particles - quantum field
theory approach | 9 pages, 2 figures. Published version | Phys.Rev.A74:042103,2006 | 10.1103/PHYSREVA.74.042103 | null | quant-ph | null | We calculate correlation function in the Einstein--Podolsky--Rosen type of
experiment with massive relativistic Dirac particles in the framework of the
quantum field theory formalism. We perform our calculations for states which
are physically interesting and transforms covariantly under the full Lorentz
group action, i.e. for pseudoscalar and vector state.
| [
{
"version": "v1",
"created": "Fri, 15 Dec 2006 12:50:47 GMT"
}
]
| 2008-11-26T00:00:00 | [
[
"Caban",
"Pawel",
""
],
[
"Rembielinski",
"Jakub",
""
]
]
|
quant-ph/0612132 | Jiangfeng Du | Hongwei Chen, Xianyi Zhou, Dieter Suter and Jiangfeng Du | Experimental Realization of $1 \to 2$ Asymmetric Phase-Covariant Quantum
Cloning | 6 pages, 5 figures | null | 10.1103/PhysRevA.75.012317 | null | quant-ph | null | While exact cloning of an unknown quantum state is prohibited by the
linearity of quantum mechanics, approximate cloning is possible and has been
used, e.g., to derive limits on the security of quantum communication
protocols. In the case of asymmetric cloning, the information from the input
state is distributed asymmetrically between the different output states. Here,
we consider asymmetric phase-covariant cloning, where the goal is to optimally
transfer the phase information from a single input qubit to different output
qubits. We construct an optimal quantum cloning machine for two qubits that
does not require ancilla qubits and implement it on an NMR quantum information
processor.
| [
{
"version": "v1",
"created": "Fri, 15 Dec 2006 13:26:54 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Chen",
"Hongwei",
""
],
[
"Zhou",
"Xianyi",
""
],
[
"Suter",
"Dieter",
""
],
[
"Du",
"Jiangfeng",
""
]
]
|
quant-ph/0612133 | Stein Olav Skr{\o}vseth | Stein Olav Skr{\o}vseth | Entanglement and its applications in systems with many degrees of
freedom | PhD thesis, 85 pages | null | null | null | quant-ph | null | Entanglement are the non-local correlations permitted by quantum theory,
believed to play a fundamental role in a quantum computer. We have investigated
these correlations in a number of theoretical models for condensed matter
systems. Such systems are likely candidates for quantum computing, and
experimentally feasible for instance as superconducting qubits. At quantum
critical points the ground state of these systems is very complicated, and the
entanglement is usually larger than at non-critical points. This entanglement
can be used to identify the critical points through what we denote the
entanglement signature, even for very small systems. From another perspective,
it seems that the entanglement is an essential tool to find an unknown ground
state, since this gives rise to a simple decomposition of the state.
| [
{
"version": "v1",
"created": "Fri, 15 Dec 2006 15:32:44 GMT"
},
{
"version": "v2",
"created": "Sun, 17 Dec 2006 10:47:22 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Skrøvseth",
"Stein Olav",
""
]
]
|
quant-ph/0612134 | Vadeiko Ilya Dr. | A.V. Rybin, I.P. Vadeiko, A. R. Bishop | Slow-light solitons: influence of relaxation | 2 figures | null | null | null | quant-ph | null | We have applied the transformation of the slow light equations to Liouville
theory that we developed in our previous work, to study the influence of
relaxation on the soliton dynamics. We solved the problem of the soliton
dynamics in the presence of relaxation and found that the spontaneous emission
from the upper atomic level is strongly suppressed. Our solution proves that
the spatial shape of the soliton is well preserved even if the relaxation time
is much shorter than the soliton time length. This fact is of great importance
for applications of the slow-light soliton concept in optical information
processing. We also demonstrate that the relaxation plays a role of resistance
to the soliton motion and slows the soliton down even if the controlling field
is constant.
| [
{
"version": "v1",
"created": "Fri, 15 Dec 2006 15:22:38 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Rybin",
"A. V.",
""
],
[
"Vadeiko",
"I. P.",
""
],
[
"Bishop",
"A. R.",
""
]
]
|
quant-ph/0612135 | Martin Hendrych | M. Hendrych, M. Micuda, and J. P. Torres | Tunable control of the bandwidth and frequency correlations of entangled
photons | 4 pages, 4 figures, submitted to Phys. Rev. Lett | null | 10.1364/OL.32.002339 | null | quant-ph | null | We demonstrate experimentally a new technique to control the bandwidth and
the type of frequency correlations (correlation, anticorrelation, and even
uncorrelation) of entangled photons generated by spontaneous parametric
downconversion. The method is based on the control of the group velocities of
the interacting waves. This technique can be applied in any nonlinear medium
and frequency band of interest. It is also demonstrated that this technique
helps enhance the quality of polarization entanglement even when femtosecond
pulses are used as a pump.
| [
{
"version": "v1",
"created": "Fri, 15 Dec 2006 16:44:27 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Hendrych",
"M.",
""
],
[
"Micuda",
"M.",
""
],
[
"Torres",
"J. P.",
""
]
]
|
quant-ph/0612136 | Christian Raabe | Christian Raabe, Stefan Scheel, and Dirk-Gunnar Welsch | Unified approach to QED in arbitrary linear media | 22 pages, no figures | null | 10.1103/PhysRevA.75.053813 | null | quant-ph | null | We give a unified approach to macroscopic QED in arbitrary linearly
responding media, based on the quite general, nonlocal form of the conductivity
tensor as it can be introduced within the framework of linear response theory,
and appropriately chosen sets of bosonic variables. The formalism generalizes
the quantization schemes that have been developed previously for diverse
classes of linear media. In particular, it turns out that the scheme developed
for locally responding linear magnetodielectric media can be recovered from the
general scheme as a limiting case for weakly spatially dispersive media. With
regard to practical applications, we furthermore address the dielectric
approximation for the conductivity tensor and the surface impedance method for
the calculation of the Green tensor of the macroscopic Maxwell equations, the
two central quantities of the theory.
| [
{
"version": "v1",
"created": "Mon, 18 Dec 2006 18:53:53 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Raabe",
"Christian",
""
],
[
"Scheel",
"Stefan",
""
],
[
"Welsch",
"Dirk-Gunnar",
""
]
]
|
quant-ph/0612137 | Fernando C. Lombardo | Fernando C. Lombardo, Diana Monteoliva and Paula I. Villar | Macroscopic tunneling, decoherence and noise-induced activation | Contribution to the Proceedings of DICE'06 | J.Phys.Conf.Ser.67:012027,2007 | 10.1088/1742-6596/67/1/012027 | null | quant-ph cond-mat.other hep-ph hep-th | null | We study the effects of the environment at zero temperature on tunneling in
an open system described by a static double-well potential. We show that the
evolution of the system in an initial Schrodinger cat state, can be summarized
in terms of three main physical phenomena, namely decoherence, quantum
tunneling and noise-induced activation. Using large-scale numerical
simulations, we obtain a detailed picture of the main stages of the evolution
and of the relevant dynamical processes
| [
{
"version": "v1",
"created": "Fri, 15 Dec 2006 21:27:34 GMT"
}
]
| 2008-11-26T00:00:00 | [
[
"Lombardo",
"Fernando C.",
""
],
[
"Monteoliva",
"Diana",
""
],
[
"Villar",
"Paula I.",
""
]
]
|
quant-ph/0612138 | Michel Brune | Stefan Kuhr, S\'ebastien Gleyzes (LKB - Lhomond), Christine Guerlin
(LKB - Lhomond), Julien Bernu (LKB - Lhomond), Ulrich Busk Hoff (LKB -
Lhomond), Samuel Del\'eglise (LKB - Lhomond), Stefano Osnaghi (LKB -
Lhomond), Michel Brune (LKB - Lhomond), Jean-Michel Raimond (LKB - Lhomond),
Serge Haroche (LKB - Lhomond), E. Jacques (DAPNIA), P. Bosland (DAPNIA), B.
Visentin (DAPNIA) | Ultrahigh finesse Fabry-Perot superconducting resonator | null | Applied Physics Letters 90 (16/04/2007) 164101 | 10.1063/1.2724816 | null | quant-ph | null | We have built a microwave Fabry-Perot resonator made of diamond-machined
copper mirrors coated with superconducting niobium. Its damping time (Tc = 130
ms at 51 GHz and 0.8 K) corresponds to a finesse of 4.6 x 109, the
highest ever reached for a Fabry-Perot in any frequency range. This result
opens novel perspectives for quantum information, decoherence and non-locality
studies.
| [
{
"version": "v1",
"created": "Sat, 16 Dec 2006 03:38:17 GMT"
},
{
"version": "v2",
"created": "Tue, 17 Jul 2007 08:54:32 GMT"
}
]
| 2007-07-17T00:00:00 | [
[
"Kuhr",
"Stefan",
"",
"LKB - Lhomond"
],
[
"Gleyzes",
"Sébastien",
"",
"LKB - Lhomond"
],
[
"Guerlin",
"Christine",
"",
"LKB - Lhomond"
],
[
"Bernu",
"Julien",
"",
"LKB - Lhomond"
],
[
"Hoff",
"Ulrich Busk",
"",
"LKB -\n Lhomond"
],
[
"Deléglise",
"Samuel",
"",
"LKB - Lhomond"
],
[
"Osnaghi",
"Stefano",
"",
"LKB -\n Lhomond"
],
[
"Brune",
"Michel",
"",
"LKB - Lhomond"
],
[
"Raimond",
"Jean-Michel",
"",
"LKB - Lhomond"
],
[
"Haroche",
"Serge",
"",
"LKB - Lhomond"
],
[
"Jacques",
"E.",
"",
"DAPNIA"
],
[
"Bosland",
"P.",
"",
"DAPNIA"
],
[
"Visentin",
"B.",
"",
"DAPNIA"
]
]
|
quant-ph/0612139 | Suresh Tiwari dr | S C Tiwari | Topological Photon | 4 pages, no figures | J.Math.Phys.49:032303,2008 | 10.1063/1.2883828 | null | quant-ph | null | We associate intrinsic energy equal to $h\nu/2$ with the spin angular
momentum of photon and propose a topological model based on orbifold in space
and tifold in time as topological obstructions. The model is substantiated
using vector wavefield disclinations. The physical photon is suggested to be a
particle like topological photon and a propagating wave such that the energy
$h\nu$ of photon is equally divided between spin energy and translational
energy corresponding to linear momentum of $h\nu/c$. The enigma of
wave-particle duality finds natural resolution and the proposed model gives new
insights into the phenomena of interference and emission of radiation.
| [
{
"version": "v1",
"created": "Sat, 16 Dec 2006 08:57:13 GMT"
}
]
| 2008-11-26T00:00:00 | [
[
"Tiwari",
"S C",
""
]
]
|
quant-ph/0612140 | Majid Mohammadi | M.Mohammadi, M.H.Naderi, M.Soltanolkotabi | Quantum statistical properties of the Jaynes-Cummings model in the
presence of a classical homogeneous gravitational field | 21 pages | null | 10.1088/1751-8113/40/6/014 | null | quant-ph | null | The temporal evolution of quantum statistical properties of an interacting
atom-radiation field system in the presence of a classical homogeneous
gravitational field is investigated within the framework of the Jaynes-Cummings
model. To analyse the dynamical evolution of the atom-radiation system a
quantum treatment of the internal and external dynamics of the atom is
presented based on an alternative su(2) dynamical algebraic structure. By
solving the Schr\"{o}dinger equation in the interaction picture, the evolving
state of the system is found by which the influence of the gravitational field
on the dynamical behavior of the atom-radiation system is explored. Assuming
that initially the radiation field is prepared in a coherent state and the
two-level atom is in a coherent superposition of the excited and ground states,
the influence of gravity on the collapses and revivals of the atomic population
inversion, atomic dipole squeezing, atomic momentum diffusion, photon counting
statistics and quadrature squeezing of the radiation field is studied.
| [
{
"version": "v1",
"created": "Sat, 16 Dec 2006 09:12:05 GMT"
},
{
"version": "v2",
"created": "Wed, 7 Mar 2007 03:03:55 GMT"
},
{
"version": "v3",
"created": "Mon, 12 Mar 2007 11:32:05 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Mohammadi",
"M.",
""
],
[
"Naderi",
"M. H.",
""
],
[
"Soltanolkotabi",
"M.",
""
]
]
|
quant-ph/0612141 | Stephen Walborn | S. P. Walborn, D. S. Tasca, M. P. Almeida, P. Pellat-Finet, C. H.
Monken and P. H. Souto Ribeiro | Violation of Bell's Inequality with Continuous Variables and Fractional
Fourier Transforms | This paper has been withdrawn | null | null | null | quant-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper has been withdrawn due to a crucial theoretical error.
| [
{
"version": "v1",
"created": "Mon, 18 Dec 2006 16:38:24 GMT"
},
{
"version": "v2",
"created": "Thu, 17 Sep 2009 14:27:08 GMT"
}
]
| 2009-09-17T00:00:00 | [
[
"Walborn",
"S. P.",
""
],
[
"Tasca",
"D. S.",
""
],
[
"Almeida",
"M. P.",
""
],
[
"Pellat-Finet",
"P.",
""
],
[
"Monken",
"C. H.",
""
],
[
"Ribeiro",
"P. H. Souto",
""
]
]
|
quant-ph/0612142 | Robert Lompay | Denys Bondar | The information theory and the collapse of a wavefunction at the
measurement of a spin 1/2 projection | latex-2e, 6 pages, 1 figure | null | null | null | quant-ph | null | From the point of view of the information theory, a model of the collapse
phenomena at the measurement of a spin 1/2 projection is developed. This model
phenomenologically includes an observer. The model allows not only to determine
the state of a system after the measurement but also to compute the state of
the observer. The state of the observer is equivalent to the operator of a spin
projection which the observer will measure at the next measurement.
| [
{
"version": "v1",
"created": "Sat, 16 Dec 2006 21:04:06 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Bondar",
"Denys",
""
]
]
|
quant-ph/0612143 | Majid Mohammadi | M.Mohammadi, M.H.Naderi, M.Soltanolkotabi | Influence of a classical homogeneous gravitational field on dissipative
dynamics of the Jaynes-Cummings model with phase damping | 25 pages, 15 figures | null | 10.1007/s10773-007-9526-8 | null | quant-ph | null | In this paper, we study the dissipative dynamics of the Jaynes-Cummings model
with phase damping in the presence of a classical homogeneous gravitational
field. The model consists of a moving two-level atom simultaneously exposed to
the gravitational field and a single-mode traveling radiation field in the
presence of the phase damping. We present a quantum treatment of the internal
and external dynamics of the atom based on an alternative su(2) dynamical
algebraic structure. By making use of the super-operator technique, we obtain
the solution of the master equation for the density operator of the quantum
system, under the Markovian approximation. Assuming that initially the
radiation field is prepared in a Glauber coherent state and the two-level atom
is in the excited state, we investigate the influence of gravity on the
temporal evolution of collapses and revivals of the atomic population
inversion, atomic dipole squeezing, atomic momentum diffusion, photon counting
statistics and quadrature squeezing of the radiation field in the presence of
phase damping.
| [
{
"version": "v1",
"created": "Sun, 17 Dec 2006 03:42:42 GMT"
},
{
"version": "v2",
"created": "Wed, 7 Mar 2007 03:15:00 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Mohammadi",
"M.",
""
],
[
"Naderi",
"M. H.",
""
],
[
"Soltanolkotabi",
"M.",
""
]
]
|
quant-ph/0612144 | Abolfazl Bayat | Abolfazl Bayat, Vahid Karimipour | Transfer of d-Level quantum states through spin chains by random
swapping | More discussion about the ground state has been added. Accepted in
Physical Review A | Phys. Rev. A 75, 022321 (2007). | 10.1103/PhysRevA.75.022321 | null | quant-ph | null | We generalize an already proposed protocol for quantum state transfer to spin
chains of arbitrary spin. An arbitrary unknown $d-$ level state is transferred
through a chain with rather good fidelity by the natural dynamics of the chain.
We compare the performance of this protocol for various values of $d$. A
by-product of our study is a much simpler method for picking up the state at
the destination as compared with the one proposed previously. We also discuss
entanglement distribution through such chains and show that the quality of
entanglement transition increases with the number of levels $d$.
| [
{
"version": "v1",
"created": "Sun, 17 Dec 2006 11:42:59 GMT"
},
{
"version": "v2",
"created": "Thu, 18 Jan 2007 14:38:11 GMT"
},
{
"version": "v3",
"created": "Wed, 24 Jan 2007 08:07:43 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Bayat",
"Abolfazl",
""
],
[
"Karimipour",
"Vahid",
""
]
]
|
quant-ph/0612145 | H. T Cui | H. T. Cui, K. Li, X. X. Yi | A Study on the Sudden Death of Entanglement | Comments and criticism are welcome. Accepted by Phys. Lett. A | Physics Letters A 365 (2007) 44?C48 | 10.1016/j.physleta.2006.12.049 | null | quant-ph | null | The dynamics of entanglement and the phenomenon of entanglement sudden death
(ESD) \cite{yu} are discussed in bipartite systems, measured by Wootters
Concurrence. Our calculation shows that ESD appears whenever the system is open
or closed and is dependent on the initial condition. The relation of the
evolution of entanglement and energy transfer between the system and its
surroundings is also studied.
| [
{
"version": "v1",
"created": "Sun, 17 Dec 2006 12:25:36 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Cui",
"H. T.",
""
],
[
"Li",
"K.",
""
],
[
"Yi",
"X. X.",
""
]
]
|
quant-ph/0612146 | Johan Aberg | Johan Aberg | Quantifying Superposition | null | null | null | null | quant-ph | null | Measures are introduced to quantify the degree of superposition in mixed
states with respect to orthogonal decompositions of the Hilbert space of a
quantum system.
These superposition measures can be regarded as analogues to entanglement
measures, but can also be put in a more direct relation to the latter. By a
second quantization of the system it is possible to induce superposition
measures from entanglement measures. We consider the measures induced from
relative entropy of entanglement and entanglement of formation. We furthermore
introduce a class of measures with an operational interpretation in terms of
interferometry. We consider the superposition measures under the action of
subspace preserving and local subspace preserving channels. The theory is
illustrated with models of an atom undergoing a relaxation process in a
Mach-Zehnder interferometer.
| [
{
"version": "v1",
"created": "Sun, 17 Dec 2006 15:06:44 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Aberg",
"Johan",
""
]
]
|
quant-ph/0612147 | Steven Jones Mr | H. M. Wiseman, S. J. Jones, and A. C. Doherty | Steering, Entanglement, Nonlocality, and the EPR Paradox | 4 pages, 1 figure. v3 updated version published in Phys. Rev. Lett | Phys. Rev. Lett. 98, 140402 (2007) | 10.1103/PhysRevLett.98.140402 | null | quant-ph | null | The concept of steering was introduced by Schrodinger in 1935 as a
generalization of the EPR paradox for arbitrary pure bipartite entangled states
and arbitrary measurements by one party. Until now, it has never been
rigorously defined, so it has not been known (for example) what mixed states
are steerable (that is, can be used to exhibit steering). We provide an
operational definition, from which we prove (by considering Werner states and
Isotropic states) that steerable states are a strict subset of the entangled
states, and a strict superset of the states that can exhibit Bell-nonlocality.
For arbitrary bipartite Gaussian states we derive a linear matrix inequality
that decides the question of steerability via Gaussian measurements, and we
relate this to the original EPR paradox.
| [
{
"version": "v1",
"created": "Mon, 18 Dec 2006 01:54:31 GMT"
},
{
"version": "v2",
"created": "Tue, 23 Jan 2007 07:23:05 GMT"
},
{
"version": "v3",
"created": "Fri, 20 Apr 2007 01:33:39 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Wiseman",
"H. M.",
""
],
[
"Jones",
"S. J.",
""
],
[
"Doherty",
"A. C.",
""
]
]
|
quant-ph/0612148 | Gary Ruben | Gary Ruben & David M. Paganin (School of Physics, Monash University) | Phase vortices from a Young's three-pinhole interferometer | 10 pages, 8 figures, REVTeX4, Submitted to Phys. Rev. E | null | 10.1103/PhysRevE.75.066613 | null | quant-ph | null | An analysis is presented of the phase vortices generated in the far field, by
an arbitrary arrangement of three monochromatic point sources of complex
spherical waves. In contrast with the case of three interfering plane waves, in
which an infinitely-extended vortex lattice is generated, the spherical sources
generate a finite number of phase vortices. Analytical expressions for the
vortex core locations are developed and shown to have a convenient
representation in a discrete parameter space. Our analysis may be mapped onto
the case of a coherently-illuminated Young's interferometer, in which the
screen is punctured by three rather than two pinholes.
| [
{
"version": "v1",
"created": "Mon, 18 Dec 2006 05:50:55 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Ruben",
"Gary",
"",
"School of Physics, Monash University"
],
[
"Paganin",
"David M.",
"",
"School of Physics, Monash University"
]
]
|
quant-ph/0612149 | Daowen Qiu | Daowen Qiu | A sufficient and necessary condition for superdense coding of quantum
states | 14 pages | International Journal of Quantum Information, 2008, 6: 1115-1125. | null | null | quant-ph | null | Recently, Harrow et al. [Phys. Rev. Lett. 92, 187901 (2004)] gave a method
for preparing an arbitrary quantum state with high success probability by
physically transmitting some qubits, and by consuming a maximally entangled
state, together with exhausting some shared random bits. In this paper, we
discover that some states are impossible to be perfectly prepared by Alice and
Bob initially sharing those entangled states that are superposed by the ground
states, as the states to be prepared. In particular, we present a sufficient
and necessary condition for the states being enabled to be exactly prepared
with probability one, in terms of the initial entangled states (maybe
nonmaximally) superposed by the ground states. In contrast, if the initially
shared entanglement is maximal, then the probabilities for preparing these
quantum states are smaller than one. Furthermore, the lower bound on the
probability for preparing some states are derived.
| [
{
"version": "v1",
"created": "Mon, 18 Dec 2006 05:07:03 GMT"
}
]
| 2010-03-10T00:00:00 | [
[
"Qiu",
"Daowen",
""
]
]
|
quant-ph/0612150 | Haijun Zhao | H. J. Zhao and M. L. Du | Oscillation structures in the spontaneous emission rate of an atom in a
medium with refractive index n between mirrors: a solvable model | 16 pages, 5 figures | null | null | null | quant-ph | null | We study the multi-periodic oscillations in the spontaneous emission rate of
an atom in a medium with refractive index n sandwiched between two parallel
mirrors. The oscillations are not obvious in the analytical formula for the
rate derived based on Fermi's golden rule but can be extracted using Fourier
transforms by varying the system scale while holding the configuration. The
oscillations are interpreted as interferences and correspond to various
closed-orbits of the emitted photon going away from and returning to the atom.
This system provides a rare example that the oscillations can be explicitly
derived by following the emitted wave until it returns to the emitting atom. We
demonstrate the summation over a large number of closed-orbits converges to the
rate formula of golden rule.
| [
{
"version": "v1",
"created": "Mon, 18 Dec 2006 08:16:30 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Zhao",
"H. J.",
""
],
[
"Du",
"M. L.",
""
]
]
|
quant-ph/0612151 | Piotr Garbaczewski | Piotr Garbaczewski | Information dynamics in quantum theory | 11 pages | Appl. Math. & Information Sciences 1, (2007), 1-12 | null | null | quant-ph | null | Shannon entropy and Fisher information functionals are known to quantify
certain information-theoretic properties of continuous probability
distributions of various origins. We carry out a systematic study of these
functionals, while assuming that the pertinent probability density has a
quantum mechanical appearance $\rho \doteq |\psi |^2$, with $\psi \in L^2(R)$.
Their behavior in time, due to the quantum Schr\"{o}dinger picture
evolution-induced dynamics of $\rho (x,t)$ is investigated as well, with an
emphasis on thermodynamical features of quantum motion.
| [
{
"version": "v1",
"created": "Mon, 18 Dec 2006 10:06:49 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Garbaczewski",
"Piotr",
""
]
]
|
quant-ph/0612152 | Stefano Longhi | Stefano Longhi | Bound states in the continuum in a single-level Fano-Anderson model | 5 figures (submitted for publication) | Eur. Phys. J. B 57, 45-51 (2007) | 10.1140/epjb/e2007-00143-2 | null | quant-ph | null | Bound states in the continuum (BIC) are shown to exist in a single-level
Fano-Anderson model with a colored interaction between the discrete state and a
tight-binding continuum, which may describe mesoscopic electron or photon
transport in a semi-infinite one-dimensional lattice. The existence of BIC is
explained in the lattice realization as a boundary effect induced by lattice
truncation.
| [
{
"version": "v1",
"created": "Mon, 18 Dec 2006 13:55:07 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Longhi",
"Stefano",
""
]
]
|
quant-ph/0612153 | Andrei Khrennikov | Andrei Khrennikov | A Mathematician's Viewpoint to Bell's theorem: In Memory of Walter
Philipp | null | Foundations of probability and physics-- 4, G. Adenier, C. Fuchs
and A. Khrennikov (eds), AIP Conference Proceedings, 889, Amer. Inst. Phys.,
Melville, NY, 2007, 7--20 | 10.1063/1.2713442 | null | quant-ph | null | In this paper dedicated to the memory of Walter Philipp, we formalize the
rules of classical$\to$ quantum correspondence and perform a rigorous
mathematical analysis of the assumptions in Bell's NO-GO arguments.
| [
{
"version": "v1",
"created": "Mon, 18 Dec 2006 14:33:06 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Khrennikov",
"Andrei",
""
]
]
|
quant-ph/0612154 | Nickolas VanMeter | N. M. VanMeter, P. Lougovski, D. B. Uskov, K. Kieling, J. Eisert, and
Jonathan P. Dowling | General linear-optical quantum state generation scheme: Applications to
maximally path-entangled states | 5 pages, 2 figures | Phys. Rev. A 76, 063808 (2007) | 10.1103/PhysRevA.76.063808 | null | quant-ph | null | We introduce schemes for linear-optical quantum state generation. A quantum
state generator is a device that prepares a desired quantum state using product
inputs from photon sources, linear-optical networks, and postselection using
photon counters. We show that this device can be concisely described in terms
of polynomial equations and unitary constraints. We illustrate the power of
this language by applying the Grobner-basis technique along with the notion of
vacuum extensions to solve the problem of how to construct a quantum state
generator analytically for any desired state, and use methods of convex
optimization to identify bounds to success probabilities. In particular, we
disprove a conjecture concerning the preparation of the maximally
path-entangled |n,0)+|0,n) (NOON) state by providing a counterexample using
these methods, and we derive a new upper bound on the resources required for
NOON-state generation.
| [
{
"version": "v1",
"created": "Mon, 18 Dec 2006 19:09:36 GMT"
},
{
"version": "v2",
"created": "Wed, 2 Jan 2008 22:55:02 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"VanMeter",
"N. M.",
""
],
[
"Lougovski",
"P.",
""
],
[
"Uskov",
"D. B.",
""
],
[
"Kieling",
"K.",
""
],
[
"Eisert",
"J.",
""
],
[
"Dowling",
"Jonathan P.",
""
]
]
|
quant-ph/0612155 | Fr\'ed\'eric Dupuis | Fr\'ed\'eric Dupuis, Patrick Hayden, Ke Li | A father protocol for quantum broadcast channels | Typo in statement of Theorem 4 fixed | IEEE Transactions on Information Theory 56(6)2946-2956, 2010 | 10.1109/TIT.2010.2046217 | null | quant-ph cs.IT math.IT | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A new protocol for quantum broadcast channels based on the fully quantum
Slepian-Wolf protocol is presented. The protocol yields an achievable rate
region for entanglement-assisted transmission of quantum information through a
quantum broadcast channel that can be considered the quantum analogue of
Marton's region for classical broadcast channels. The protocol can be adapted
to yield achievable rate regions for unassisted quantum communication and for
entanglement-assisted classical communication; in the case of unassisted
transmission, the region we obtain has no independent constraint on the sum
rate, only on the individual transmission rates. Regularized versions of all
three rate regions are provably optimal.
| [
{
"version": "v1",
"created": "Tue, 19 Dec 2006 20:29:06 GMT"
},
{
"version": "v2",
"created": "Wed, 18 Apr 2007 17:46:39 GMT"
},
{
"version": "v3",
"created": "Mon, 31 Jan 2011 09:51:18 GMT"
},
{
"version": "v4",
"created": "Wed, 10 Oct 2012 10:27:02 GMT"
}
]
| 2012-10-11T00:00:00 | [
[
"Dupuis",
"Frédéric",
""
],
[
"Hayden",
"Patrick",
""
],
[
"Li",
"Ke",
""
]
]
|
quant-ph/0612156 | Gerald Gilbert | G. Gilbert, M. Hamrick and Y.S. Weinstein | On the use of photonic N00N states for practical quantum interferometry | 14 pages, 7 figures | JOSA B, Vol. 25, Issue 8, pp. 1336-1340, 2008 | null | null | quant-ph | null | The performance of photonic $N00N$ states, propagating in an attenuating
medium, is analyzed with respect to phase estimation. It is shown that, for
$N00N$ states propagating through a lossy medium, the Heisenberg limit is never
achieved. It is also shown that, for a given value of $N$, a signal comprised
of an attenuated separable state of $N$ photons will actually produce a better
phase estimate than will a signal comprised of an equally attenuated $N00N$
state, unless the transmittance of the medium is very high. This is a
consequence of the need to utilize measurement operators appropriate to the
different signal states. The result is that, for most practical applications in
realistic scenarios with attenuation, the resolution of $N00N$ state-based
phase estimation not only does not achieve the Heisenberg Limit, but is
actually worse than the Standard Quantum Limit. It is demonstrated that this
performance deficit becomes more pronounced as the number, $N$, of photons in
the signal increases.
| [
{
"version": "v1",
"created": "Tue, 19 Dec 2006 19:22:07 GMT"
}
]
| 2008-07-30T00:00:00 | [
[
"Gilbert",
"G.",
""
],
[
"Hamrick",
"M.",
""
],
[
"Weinstein",
"Y. S.",
""
]
]
|
quant-ph/0612157 | Jing Zhang | Haixia Chen, Jing Zhang | Continuous-Variable Quantum Cloning of Coherent states with
Phase-Conjugate Input Modes Using Linear Optics | 6 pages, 3 figures. appear in Phys. Rev. A | Phys. Rev. A 75, 022306 (2007) | 10.1103/PhysRevA.75.022306 | null | quant-ph | null | We propose a scheme for continuous-variable quantum cloning of coherent
states with phase-conjugate input modes using linear optics. The quantum
cloning machine yields $M$ identical optimal clones from $N$ replicas of a
coherent state and $N$ its replicas of phase conjugate. This scheme can be
straightforwardly implemented with the setup accessible at present since its
optical implementation only employs simple linear optical elements and homodyne
detection. Compared with the original scheme for continuous variables quantum
cloning with phase-conjugate input modes proposed by Cerf and Iblisdir [Phys.
Rev. Lett. 87, 247903 (2001)], which utilized a nondegenerate optical
parametric amplifier, our scheme loses the output of phase-conjugate clones and
is regarded as irreversible quantum cloning.
| [
{
"version": "v1",
"created": "Tue, 19 Dec 2006 00:43:05 GMT"
}
]
| 2009-11-13T00:00:00 | [
[
"Chen",
"Haixia",
""
],
[
"Zhang",
"Jing",
""
]
]
|
quant-ph/0612158 | Yukihiro Ota | Yukihiro Ota, Shuji Mikami, Motoyuki Yoshida, Ichiro Ohba | Attainable entanglement of unitary transformed thermal states in
liquid-state nuclear magnetic resonance with the chemical shift | 9 pages, 1 figures. There were mistakes in the previous version. The
main results don't change, but our motivation has to be reconsidered | J. Phys. A: Math. Theor. 40, (2007) 14263-14277. | 10.1088/1751-8113/40/47/016 | null | quant-ph | null | Recently, Yu, Brown, and Chuang [Phys. Rev. A {\bf 71}, 032341 (2005)]
investigated the entanglement attainable from unitary transformed thermal
states in liquid-state nuclear magnetic resonance (NMR). Their research gave an
insight into the role of the entanglement in a liquid-state NMR quantum
computer. Moreover, they attempted to reveal the role of mixed-state
entanglement in quantum computing. However, they assumed that the Zeeman energy
of each nuclear spin which corresponds to a qubit takes a common value for all;
there is no chemical shift. In this paper, we research a model with the
chemical shifts and analytically derive the physical parameter region where
unitary transformed thermal states are entangled, by the positive partial
transposition (PPT) criterion with respect to any bipartition. We examine the
effect of the chemical shifts on the boundary between the separability and the
nonseparability, and find it is negligible.
| [
{
"version": "v1",
"created": "Tue, 19 Dec 2006 07:06:35 GMT"
},
{
"version": "v2",
"created": "Wed, 20 Dec 2006 05:01:32 GMT"
},
{
"version": "v3",
"created": "Thu, 5 Apr 2007 12:25:17 GMT"
}
]
| 2007-11-10T00:00:00 | [
[
"Ota",
"Yukihiro",
""
],
[
"Mikami",
"Shuji",
""
],
[
"Yoshida",
"Motoyuki",
""
],
[
"Ohba",
"Ichiro",
""
]
]
|
quant-ph/0612159 | Onur Hosten | Onur Hosten and Paul G. Kwiat | Weak Measurements and Counterfactual Computation | 2 pages | null | null | null | quant-ph | null | Vaidman, in a recent article adopts the method of 'quantum weak measurements
in pre- and postselected ensembles' to ascertain whether or not the
chained-Zeno counterfactual computation scheme proposed by Hosten et al. is
counterfactual; which has been the topic of a debate on the definition of
counterfactuality. We disagree with his conclusion, which brings up some
interesting aspects of quantum weak measurements and some concerns about the
way they are interpreted.
| [
{
"version": "v1",
"created": "Tue, 19 Dec 2006 08:02:20 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"Hosten",
"Onur",
""
],
[
"Kwiat",
"Paul G.",
""
]
]
|
quant-ph/0612160 | Zhijiao Deng | Z. J. Deng, K. L. Gao, F. Mang | Alternative scheme for two-qubit conditional phase gate by adiabatic
passage under dissipation | to appear in J. Phys. B | null | 10.1088/0953-4075/40/2/008 | null | quant-ph | null | We check a recent proposal [H. Goto and K. Ichimura Phys. Rev. A 70, 012305
(2004)] for controlled phase gate through adiabatic passage under the influence
of spontaneous emission and the cavity decay. We show a modification of above
proposal could be used to generate the necessary conditional phase gates in the
two-qubit Grover search. Conditioned on no photon leakage either from the
atomic excited state or from the cavity mode during the gating period, we
numerically analyze the success probability and the fidelity of the two-qubit
conditional phase gate by adiabatic passage. The comparison made between our
proposed gating scheme and a previous one shows that Goto and Ichimura's scheme
is an alternative and feasible way in the optical cavity regime for two-qubit
gates and could be generalised in principle to multi-qubit gates.
| [
{
"version": "v1",
"created": "Tue, 19 Dec 2006 08:38:44 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Deng",
"Z. J.",
""
],
[
"Gao",
"K. L.",
""
],
[
"Mang",
"F.",
""
]
]
|
quant-ph/0612161 | Zhijiao Deng | Z.J. Deng, K.L. Gao, M. Feng | Generation of N-qubit W state with rf-SQUID qubits by adiabatic passage | to appear in Phys. Rev. A | null | 10.1103/PhysRevA.74.064303 | null | quant-ph | null | A simple scheme is presented to generate n-qubit W state with
rf-superconducting quantum interference devices (rf-SQUIDs) in cavity QED
through adiabatic passage. Because of the achievable strong coupling for
rf-SQUID qubits embedded in cavity QED, we can get the desired state with high
success probability. Furthermore, the scheme is insensitive to position
inaccuracy of the rf-SQUIDs. The numerical simulation shows that, by using
present experimental techniques, we can achieve our scheme with very high
success probability, and the fidelity could be eventually unity with the help
of dissipation.
| [
{
"version": "v1",
"created": "Tue, 19 Dec 2006 09:03:56 GMT"
}
]
| 2015-06-26T00:00:00 | [
[
"Deng",
"Z. J.",
""
],
[
"Gao",
"K. L.",
""
],
[
"Feng",
"M.",
""
]
]
|
quant-ph/0612162 | Giacomo Mauro D'Ariano | Giacomo Mauro D'Ariano | Where the mathematical structure of Quantum Mechanics coms from | Work presented at the conference "Beyond the Quantum" held at the
Lorentz Center in Leiden from May 29th through June 2nd 2006. Synthesis of
quant-ph/0611094 | null | null | null | quant-ph | null | The mathematical formulation of Quantum Mechanics is derived from purely
operational axioms based on a general definition of "experiment" as a set of
transformations. The main ingredient of the mathematical construction 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 "adjoint" of a transformation.
| [
{
"version": "v1",
"created": "Tue, 19 Dec 2006 18:43:15 GMT"
}
]
| 2007-05-23T00:00:00 | [
[
"D'Ariano",
"Giacomo Mauro",
""
]
]
|
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