Recent from PRA
Recently published articles in Phys. Rev. A in the Table of Content section "Quantum information"
URL: http://pra.aps.org/
Updated: 6 hours 22 min ago
Local noise can enhance two-qubit teleportation
Author(s): Ye Yeo
For single-qubit teleportation, it has been shown that there is a family of two-qubit mixed states whose teleportation fidelity can be enhanced by subjecting one of the qubits to an amplitude damping channel. This is an interesting result, since noise in general degrades quantum entanglement. It is ...
[Phys. Rev. A 78, 022334] Published Mon Aug 25, 2008
For single-qubit teleportation, it has been shown that there is a family of two-qubit mixed states whose teleportation fidelity can be enhanced by subjecting one of the qubits to an amplitude damping channel. This is an interesting result, since noise in general degrades quantum entanglement. It is ...
[Phys. Rev. A 78, 022334] Published Mon Aug 25, 2008
Operator quantum error correction for continuous dynamics
Author(s): Ognyan Oreshkov, Daniel A. Lidar, and Todd A. Brun
We study the conditions under which a subsystem code is correctable in the presence of noise that results from continuous dynamics. We consider the case of Markovian dynamics as well as the general case of Hamiltonian dynamics of the system and the environment, and derive necessary and sufficient co...
[Phys. Rev. A 78, 022333] Published Fri Aug 22, 2008
We study the conditions under which a subsystem code is correctable in the presence of noise that results from continuous dynamics. We consider the case of Markovian dynamics as well as the general case of Hamiltonian dynamics of the system and the environment, and derive necessary and sufficient co...
[Phys. Rev. A 78, 022333] Published Fri Aug 22, 2008
Quantum computers can search rapidly by using almost any selective transformation
Author(s): Avatar Tulsi
The search problem is to find a state satisfying certain properties out of a given set. Grover’s algorithm drives a quantum computer from a prepared initial state to the target state and solves the problem quadratically faster than a classical computer. The algorithm uses selective transformations...
[Phys. Rev. A 78, 022332] Published Fri Aug 22, 2008
The search problem is to find a state satisfying certain properties out of a given set. Grover’s algorithm drives a quantum computer from a prepared initial state to the target state and solves the problem quadratically faster than a classical computer. The algorithm uses selective transformations...
[Phys. Rev. A 78, 022332] Published Fri Aug 22, 2008
Dispersive coupling between the superconducting transmission line resonator and the double quantum dots
Author(s): Guo-Ping Guo, Hui Zhang, Yong Hu, Tao Tu, and Guang-Can Guo
Realization of controllable interaction between distant qubits is one of the major problems in scalable solid-state quantum computing. We study a superconducting transmission line resonator (TLR) as a tunable dispersive coupler for the double-dot molecules. A general interaction Hamiltonian of n two...
[Phys. Rev. A 78, 020302] Published Fri Aug 22, 2008
Realization of controllable interaction between distant qubits is one of the major problems in scalable solid-state quantum computing. We study a superconducting transmission line resonator (TLR) as a tunable dispersive coupler for the double-dot molecules. A general interaction Hamiltonian of n two...
[Phys. Rev. A 78, 020302] Published Fri Aug 22, 2008
Geometric phases and Bloch-sphere constructions for SU(N) groups with a complete description of the SU(4) group
Author(s): D. Uskov and A. R. Rau
A two-sphere (“Bloch” or ‘‘Poincare’’) is familiar for describing the dynamics of a spin- 1∕2 particle or light polarization. Analogous objects are derived for unitary groups larger than SU(2) through an iterative procedure that constructs evolution operators for higher-dimensional SU(...
[Phys. Rev. A 78, 022331] Published Thu Aug 21, 2008
A two-sphere (“Bloch” or ‘‘Poincare’’) is familiar for describing the dynamics of a spin- 1∕2 particle or light polarization. Analogous objects are derived for unitary groups larger than SU(2) through an iterative procedure that constructs evolution operators for higher-dimensional SU(...
[Phys. Rev. A 78, 022331] Published Thu Aug 21, 2008
Analog Grover search by adiabatic passage in a cavity-laser-atom system
Author(s): D. Daems and S. Guérin
A physical implementation of the adiabatic Grover search is theoretically investigated in a system of N identical three-level atoms trapped in a single-mode cavity. Some of the atoms are marked through the presence of an energy gap between their two ground states. The search is controlled by two par...
[Phys. Rev. A 78, 022330] Published Wed Aug 20, 2008
A physical implementation of the adiabatic Grover search is theoretically investigated in a system of N identical three-level atoms trapped in a single-mode cavity. Some of the atoms are marked through the presence of an energy gap between their two ground states. The search is controlled by two par...
[Phys. Rev. A 78, 022330] Published Wed Aug 20, 2008
Three fermions with six single-particle states can be entangled in two inequivalent ways
Author(s): Péter Lévay and Péter Vrana
Using a generalization of Cayley’s hyperdeterminant as a new measure of tripartite fermionic entanglement we obtain the SLOCC classification of three-fermion systems with six “single-particle” states. A special subclass of such three-fermion systems is shown to have the same properties as the ...
[Phys. Rev. A 78, 022329] Published Wed Aug 20, 2008
Using a generalization of Cayley’s hyperdeterminant as a new measure of tripartite fermionic entanglement we obtain the SLOCC classification of three-fermion systems with six “single-particle” states. A special subclass of such three-fermion systems is shown to have the same properties as the ...
[Phys. Rev. A 78, 022329] Published Wed Aug 20, 2008
Experimental quantum key distribution based on a Bell test
Author(s): Alexander Ling, Matthew P. Peloso, Ivan Marcikic, Valerio Scarani, Antía Lamas-Linares, and Christian Kurtsiefer
We report on a complete free-space field implementation of a modified Ekert protocol for quantum key distribution using entangled photon pairs. For each photon pair we perform a random choice between key generation and a Bell inequality. The amount of violation is used to determine the possible know...
[Phys. Rev. A 78, 020301] Published Wed Aug 20, 2008
We report on a complete free-space field implementation of a modified Ekert protocol for quantum key distribution using entangled photon pairs. For each photon pair we perform a random choice between key generation and a Bell inequality. The amount of violation is used to determine the possible know...
[Phys. Rev. A 78, 020301] Published Wed Aug 20, 2008
Efficient generation of random multipartite entangled states using time-optimal unitary operations
Author(s): A. Borras, A. P. Majtey, and M. Casas
We review the generation of random pure states using a protocol of repeated two-qubit gates. We study the dependence of the convergence to states with Haar multipartite entanglement distribution. We investigate the optimal generation of such states in terms of the physical (real) time needed to appl...
[Phys. Rev. A 78, 022328] Published Tue Aug 19, 2008
We review the generation of random pure states using a protocol of repeated two-qubit gates. We study the dependence of the convergence to states with Haar multipartite entanglement distribution. We investigate the optimal generation of such states in terms of the physical (real) time needed to appl...
[Phys. Rev. A 78, 022328] Published Tue Aug 19, 2008
Induced entanglement enhanced by quantum criticality
Author(s): Qing Ai, Tao Shi, Guilu Long, and C. P. Sun
Two-qubit entanglement can be induced by a quantum data bus interacting with them. In this paper, with the quantum spin chain in the transverse field as an illustration of the quantum data bus, we show that such induced entanglement can be enhanced by the quantum phase transition (QPT) of the quantu...
[Phys. Rev. A 78, 022327] Published Tue Aug 19, 2008
Two-qubit entanglement can be induced by a quantum data bus interacting with them. In this paper, with the quantum spin chain in the transverse field as an illustration of the quantum data bus, we show that such induced entanglement can be enhanced by the quantum phase transition (QPT) of the quantu...
[Phys. Rev. A 78, 022327] Published Tue Aug 19, 2008
Loss in hybrid qubit-bus couplings and gates
Author(s): Sebastien G. Louis, W. J. Munro, T. P. Spiller, and Kae Nemoto
We provide a characterization and analysis of the effects of dissipation on oscillator assisted (qubus) quantum gates. The effects can be understood and minimized by looking at the dynamics of the signal coherence and its entanglement with the continuous variable probe. Adding loss in between succes...
[Phys. Rev. A 78, 022326] Published Tue Aug 19, 2008
We provide a characterization and analysis of the effects of dissipation on oscillator assisted (qubus) quantum gates. The effects can be understood and minimized by looking at the dynamics of the signal coherence and its entanglement with the continuous variable probe. Adding loss in between succes...
[Phys. Rev. A 78, 022326] Published Tue Aug 19, 2008
Perfect state transfer in long-range interacting spin chains
Author(s): Giulia Gualdi, Vojtech Kostak, Irene Marzoli, and Paolo Tombesi
We investigate the most general conditions under which a finite ferromagnetic long-range interacting spin chain achieves unitary fidelity and the shortest transfer time in transmitting an unknown input qubit. A deeper insight into system dynamics, allows us to identify an ideal system involving send...
[Phys. Rev. A 78, 022325] Published Mon Aug 18, 2008
We investigate the most general conditions under which a finite ferromagnetic long-range interacting spin chain achieves unitary fidelity and the shortest transfer time in transmitting an unknown input qubit. A deeper insight into system dynamics, allows us to identify an ideal system involving send...
[Phys. Rev. A 78, 022325] Published Mon Aug 18, 2008
Schmidt measure is not fully additive for pure states
Author(s): W. Huang and Zhaohui Wei
The Schmidt measure was introduced as a tool to quantify the degree of multipartite entanglement, which is a natural generalization of the Schmidt rank for a bipartite system and is particularly suitable for characterizing the multiparticle entanglement of graph states and other quantum states with ...
[Phys. Rev. A 78, 024304] Published Fri Aug 15, 2008
The Schmidt measure was introduced as a tool to quantify the degree of multipartite entanglement, which is a natural generalization of the Schmidt rank for a bipartite system and is particularly suitable for characterizing the multiparticle entanglement of graph states and other quantum states with ...
[Phys. Rev. A 78, 024304] Published Fri Aug 15, 2008
Hitting time for the continuous quantum walk
Author(s): Martin Varbanov, Hari Krovi, and Todd A. Brun
We define the hitting (or absorbing) time for the case of continuous quantum walks by measuring the walk at random times, according to a Poisson process with measurement rate λ . From this definition we derive an explicit formula for the hitting time, and explore its dependence on the measurement r...
[Phys. Rev. A 78, 022324] Published Fri Aug 15, 2008
We define the hitting (or absorbing) time for the case of continuous quantum walks by measuring the walk at random times, according to a Poisson process with measurement rate λ . From this definition we derive an explicit formula for the hitting time, and explore its dependence on the measurement r...
[Phys. Rev. A 78, 022324] Published Fri Aug 15, 2008
Classical states versus separable states
Author(s): Nan Li and Shunlong Luo
A bipartite state is called classical (with regard to correlations) if it is left undisturbed by a certain local von Neumann measurement, and is called separable if it can be represented as a convex combination of product states. Due to the perfect distinguishability of orthogonal vectors, a classic...
[Phys. Rev. A 78, 024303] Published Thu Aug 14, 2008
A bipartite state is called classical (with regard to correlations) if it is left undisturbed by a certain local von Neumann measurement, and is called separable if it can be represented as a convex combination of product states. Due to the perfect distinguishability of orthogonal vectors, a classic...
[Phys. Rev. A 78, 024303] Published Thu Aug 14, 2008
Quantum nodes for W-state generation in noisy channels
Author(s): Jie Song, Yan Xia, and He-Shan Song
A scheme for generating W state by using single-photon interference and time-bin encoding in polarization noise channels is proposed. We show that polarization noise cannot affect the fidelity of the intended entangled state generation, and that the successful probability does not change as the numb...
[Phys. Rev. A 78, 024302] Published Thu Aug 14, 2008
A scheme for generating W state by using single-photon interference and time-bin encoding in polarization noise channels is proposed. We show that polarization noise cannot affect the fidelity of the intended entangled state generation, and that the successful probability does not change as the numb...
[Phys. Rev. A 78, 024302] Published Thu Aug 14, 2008
Heralded generation of entanglement with coupled cavities
Author(s): Jaeyoon Cho, Dimitris G. Angelakis, and Sougato Bose
We propose a scheme to generate two-photon, two-atom, or atom-photon entangled states with a coupled system of two cavities. In our scheme, two cavity photons are exchanged by the direct intercavity coupling, while atoms in the cavities simply generate and probe them. By virtue of the high efficienc...
[Phys. Rev. A 78, 022323] Published Thu Aug 14, 2008
We propose a scheme to generate two-photon, two-atom, or atom-photon entangled states with a coupled system of two cavities. In our scheme, two cavity photons are exchanged by the direct intercavity coupling, while atoms in the cavities simply generate and probe them. By virtue of the high efficienc...
[Phys. Rev. A 78, 022323] Published Thu Aug 14, 2008
Experimental investigation of the dynamics of entanglement: Sudden death, complementarity, and continuous monitoring of the environment
Author(s): A. Salles, F. de Melo, M. P. Almeida, M. Hor-Meyll, S. P. Walborn, P. H. Souto Ribeiro, and L. Davidovich
We report on an experimental investigation of the dynamics of entanglement between a single qubit and its environment, as well as for pairs of qubits interacting independently with individual environments, using photons obtained from parametric down-conversion. The qubits are encoded in the polariza...
[Phys. Rev. A 78, 022322] Published Wed Aug 13, 2008
We report on an experimental investigation of the dynamics of entanglement between a single qubit and its environment, as well as for pairs of qubits interacting independently with individual environments, using photons obtained from parametric down-conversion. The qubits are encoded in the polariza...
[Phys. Rev. A 78, 022322] Published Wed Aug 13, 2008
Efficient quantum key distribution over a collective noise channel
Author(s): Xi-Han Li, Fu-Guo Deng, and Hong-Yu Zhou
We present two efficient quantum key distribution schemes over two different collective-noise channels. The accepted hypothesis of collective noise is that photons travel inside a time window small compared to the variation of noise. Noiseless subspaces are made up of two Bell states and the spatial...
[Phys. Rev. A 78, 022321] Published Wed Aug 13, 2008
We present two efficient quantum key distribution schemes over two different collective-noise channels. The accepted hypothesis of collective noise is that photons travel inside a time window small compared to the variation of noise. Noiseless subspaces are made up of two Bell states and the spatial...
[Phys. Rev. A 78, 022321] Published Wed Aug 13, 2008
Discrimination of the binary coherent signal: Gaussian-operation limit and simple non-Gaussian near-optimal receivers
Author(s): Masahiro Takeoka and Masahide Sasaki
We address the limit of the Gaussian operations and classical communication in the problem of quantum state discrimination. We show that the optimal Gaussian strategy for the discrimination of the binary phase shift keyed (BPSK) coherent signal is a simple homodyne detection. We also propose practic...
[Phys. Rev. A 78, 022320] Published Wed Aug 13, 2008
We address the limit of the Gaussian operations and classical communication in the problem of quantum state discrimination. We show that the optimal Gaussian strategy for the discrimination of the binary phase shift keyed (BPSK) coherent signal is a simple homodyne detection. We also propose practic...
[Phys. Rev. A 78, 022320] Published Wed Aug 13, 2008