Electronic entanglement via quantum Hall interferometry in analogy to an optical method
Diego Frustaglia and Adan Cabello
We present an interferometric scheme producing orbital entanglement in a quantum Hall system upon electron-hole pair emission via tunneling. The proposed setup is an electronic version of the optical interferometer proposed by Cabello et al. [Phys. Rev. Lett. 102, 040401 (2009)] and is feasible with ... [Phys. Rev. B 80, 201312 (2009)] published Fri Nov 20, 2009.
Correlated two-photon emission by transitions of Dirac-Volkov states in intense laser fields: QED predictions
Erik Lotstedt and Ulrich D. Jentschura
In an intense laser field, an electron may decay by emitting a pair of photons. The two photons emitted during the process, which can be interpreted as a laser-dressed double Compton scattering, remain entangled in a quantifiable way: namely, the so-called concurrence of the photon polarizations giv ... [Phys. Rev. A 80, 053419 (2009)] published Fri Nov 20, 2009.
Nonequilibrium thermal entanglement in a three-qubit XX model
X. L. Huang (黄晓理), J. L. Guo (郭金良), and X. X. Yi (衣学喜)
Making use of the master equation and effective Hamiltonian approach, we investigate the steady-state entanglement in a three-qubit XX model. Both symmetric and nonsymmetric qubit-qubit couplings are considered. The system (the three qubits) is coupled to two bosonic baths at different temperatures. ... [Phys. Rev. A 80, 054301 (2009)] published Mon Nov 16, 2009.
Some applications of the fractional Poisson probability distribution
Nick Laskin
Physical and mathematical applications of the recently invented fractional Poisson probability distribution have been presented. As a physical application, a new family of quantum coherent states has been introduced and studied. As mathematical applications, we have developed the fractional generali ... [J. Math. Phys. 50, 113513 (2009)] published Mon Nov 16, 2009.
Characterization of partial positive transposition states and measures of entanglement
Wladyslaw A. Majewski, Takashi Matsuoka, and Masanori Ohya
A detailed characterization of partial positive transposition (PPT) states, both in the Heisenberg and in the Schrodinger picture, is given. Measures of entanglement are defined and discussed in details. Illustrative examples are provided. ... [J. Math. Phys. 50, 113509 (2009)] published Thu Nov 12, 2009.
Maximally entangled three-qubit states via geometric measure of entanglement
Sayatnova Tamaryan, Tzu-Chieh Wei, and DaeKil Park
Bipartite maximally entangled states have the property that the largest Schmidt coefficient reaches its lower bound. However, for multipartite states, the standard Schmidt decomposition generally does not exist. We use a generalized Schmidt decomposition and the geometric measure of entanglement to ... [Phys. Rev. A 80, 052315 (2009)] published Wed Nov 11, 2009.
Topological order in paired states of fermions in two dimensions with breaking of parity and time-reversal symmetries
Noah Bray-Ali, Letian Ding, and Stephan Haas
We numerically evaluate the entanglement spectrum (singular value decomposition of the wave function) of paired states of fermions in two dimensions that break parity and time-reversal symmetries, focusing on the spin-polarized p+ip case. The entanglement spectrum of the weak-pairing (BCS) phase con ... [Phys. Rev. B 80, 180504 (2009)] published Wed Nov 11, 2009.
Non-Gaussian State Generation from Linear Elements via Feedback
Masahiro Yanagisawa
We present a feedback scheme to produce quantum non-Gaussian states from linear optical elements. Instead of traditional additive control methods, we introduce a mutiplicative feedback control and apply it to the deterministic generation of quantum superposition states. The protocol of feedback cont ... [Phys. Rev. Lett. 103, 203601 (2009)] published Wed Nov 11, 2009.
Effects of squeezing on quantum nonlocality of superpositions of coherent states
Chang-Woo Lee and Hyunseok Jeong
We analyze effects of squeezing upon superpositions of coherent states (SCSs) and entangled coherent states for Bell-inequality tests. We find that external squeezing can always increase the degrees of Bell violations, if the squeezing direction is properly chosen, for the case of photon parity meas ... [Phys. Rev. A 80, 052105 (2009)] published Tue Nov 10, 2009.
General algorithm for manipulating nonlinear and linear entanglement witnesses by using exact convex optimization
M. A. Jafarizadeh, K. Aghayar, and A. Heshmati
We consider the problem of obtaining the entanglement witnesses for a given quantum system. We present a method to convert this problem to a standard convex optimization problem by defining a feasible region. Then we develop a generic two-step algorithm for this problem which can be applied to the e ... [Phys. Rev. A 80, 052307 (2009)] published Mon Nov 9, 2009.
Inseparability criteria based on matrices of moments
Adam Miranowicz, Marco Piani, Pawel Horodecki, and Ryszard Horodecki
Inseparability criteria for continuous and discrete bipartite quantum states based on moments of annihilation and creation operators are studied by developing the idea of Shchukin-Vogel criterion [Phys. Rev. Lett. 95, 230502 (2005)]. If a state is separable, then the corresponding matrix of moments ... [Phys. Rev. A 80, 052303 (2009)] published Tue Nov 3, 2009.
Concavity of the set of quantum probabilities for any given dimension
Karoly F. Pal and Tamas Vertesi
Let us consider the set of all probabilities generated by local binary measurements on two separated quantum systems of a given local dimension d. We address the question of whether the shape of this quantum body is convex or not. We construct a point in the space of probabilities, which is on the c ... [Phys. Rev. A 80, 042114 (2009)] published Fri Oct 30, 2009.
Testing for Multipartite Quantum Nonlocality Using Functional Bell Inequalities
Q. Y. He, E. G. Cavalcanti, M. D. Reid, and P. D. Drummond
We show that arbitrary functions of continuous variables, e.g., position and momentum, can be used to generate tests that distinguish quantum theory from local hidden variable theories. By optimizing these functions, we obtain more robust violations of local causality than obtained previously. We an ... [Phys. Rev. Lett. 103, 180402 (2009)] published Thu Oct 29, 2009.
Steady-state two-atom entanglement in a pumped cavity
Hideomi Nihira and C. R. Stroud, Jr.
In this paper we explore the possibility of a steady-state entanglement of two two-level atoms inside a pumped cavity by taking into account cavity leakage and the spontaneous emission of photons by the atoms. We describe the system in the dressed state picture in which the coherence is built into t ... [Phys. Rev. A 80, 042329 (2009)] published Tue Oct 27, 2009.
Cavity-assisted fast generation of entangled photon pairs through the biexciton-exciton cascade
P. K. Pathak and S. Hughes
We present a scheme for the fast cavity-assisted generation of entangled photon pairs from a single quantum dot coupled to a planar photonic crystal that support two orthogonally polarized cavity modes. We discuss within generation and across generation of entangled photons when both the biexciton t ... [Phys. Rev. B 80, 155325 (2009)] published Mon Oct 26, 2009.
Quantum hypothesis testing with group symmetry
Fumio Hiai, Milan Mosonyi, and Masahito Hayashi
The asymptotic discrimination problem of two quantum states is studied in the setting where measurements are required to be invariant under some symmetry group of the system. We consider various asymptotic error exponents in connection with the problems of the Chernoff bound, the Hoeffding bound, an ... [J. Math. Phys. 50, 103304 (2009)] published Thu Oct 22, 2009.
Ground-state entanglement in a coupled-cavity model
E. K. Irish
Bipartite entanglement entropies are calculated for the ground state of the two-excitation subspace in a two-site coupled cavity model. Each region in the phase diagram (atomic insulator, polaritonic insulator, photonic superfluid, and polaritonic superfluid) is found to be characterized by unique e ... [Phys. Rev. A 80, 043825 (2009)] published Wed Oct 21, 2009.
Cluster-type entangled coherent states: Generation and application
Nguyen Ba An and Jaewan Kim
We consider a type of (M+N)-mode entangled coherent states and propose a simple deterministic scheme to generate these states that can fly freely in space. We then exploit such free-flying states to teleport certain kinds of superpositions of multimode coherent states. We also address the issue of m ... [Phys. Rev. A 80, 042316 (2009)] published Tue Oct 20, 2009.
Spectral conditions for entanglement witnesses versus bound entanglement
Dariusz Chruścinski, Andrzej Kossakowski, and Gniewomir Sarbicki
It is shown that entanglement witnesses constructed via the family of spectral conditions are decomposable, i.e., cannot be used to detect bound entanglement. It supports several observations that bound entanglement reveals highly nonspectral features. ... [Phys. Rev. A 80, 042314 (2009)] published Mon Oct 19, 2009.
Time-reversal frameness and superselection
Gilad Gour, Barry C. Sanders, and Peter S. Turner
We show that appropriate superpositions of motional states are a reference frame resource that enables breaking of time-reversal superselection so that two parties lacking knowledge about the other's direction of time can still communicate. We identify the time-reversal reference frame resource stat ... [J. Math. Phys. 50, 102105 (2009)] published Mon Oct 19, 2009.
State-Independent Quantum Contextuality with Single Photons
Elias Amselem, Magnus Radmark, Mohamed Bourennane, and Adan Cabello
We present an experimental state-independent violation of an inequality for noncontextual theories on single particles. We show that 20 different single-photon states violate an inequality which involves correlations between results of sequential compatible measurements by at least 419 standard devi ... [Phys. Rev. Lett. 103, 160405 (2009)] published Fri Oct 16, 2009.