Perfect Distinguishability of Quantum Operations
Runyao Duan, Yuan Feng, and Mingsheng Ying
We provide a feasible necessary and sufficient condition for when an unknown quantum operation (quantum device) secretly selected from a set of known quantum operations can be identified perfectly within a finite number of queries, and thus complete the characterization of the perfect distinguishabi ... [Phys. Rev. Lett. 103, 210501 (2009)] published Fri Nov 20, 2009.
Communication in quantum networks of logical bus topology
T. Brougham, G. M. Nikolopoulos, and I. Jex
Perfect state transfer (PST) is discussed in the context of passive quantum networks with logical bus topology, where many logical nodes communicate using the same shared media without any external control. The conditions under which a number of point-to-point PST links may serve as building blocks ... [Phys. Rev. A 80, 052325 (2009)] published Thu Nov 19, 2009.
Discrimination with error margin between two states: Case of general occurrence probabilities
H. Sugimoto, T. Hashimoto, M. Horibe, and A. Hayashi
We investigate a state discrimination problem which interpolates minimum error and unambiguous discrimination by introducing a margin for the probability of error. We closely analyze discrimination of two pure states with general occurrence probabilities. The optimal measurements are classified into ... [Phys. Rev. A 80, 052322 (2009)] published Tue Nov 17, 2009.
NMR multiple quantum coherences in quasi-one-dimensional spin systems: Comparison with ideal spin-chain dynamics
Wenxian Zhang, Paola Cappellaro, Natania Antler, Brian Pepper, David G. Cory et al.
The F spins in a crystal of fluorapatite have often been used to experimentally approximate a one-dimensional spin system. Under suitable multipulse control, the nuclear-spin dynamics may be modeled to first approximation by a double-quantum one-dimensional Hamiltonian, which is analytically solvabl ... [Phys. Rev. A 80, 052323 (2009)] published Tue Nov 17, 2009.
Generation of polarization-entangled photons using type-II doubly periodically poled lithium niobate waveguides
K. Thyagarajan, J. Lugani, S. Ghosh, K. Sinha, A. Martin et al.
In this paper, we address the issue of the generation of nondegenerate cross-polarization-entangled photon pairs using type-II periodically poled lithium niobate. We show that, by an appropriate engineering of the quasi-phase-matching grating, it is possible to simultaneously satisfy the conditions ... [Phys. Rev. A 80, 052321 (2009)] published Fri Nov 13, 2009.
Students' Understanding of Stern Gerlach Experiment
Guangtian Zhu and Chandralekha Singh
The Stern Gerlach experiment has played a central role in the discovery of spin angular momentum and it has also played a pivotal role in elucidating foundational issues in quantum mechanics. Here, we discuss investigation of students' difficulties related to the Stern Gerlach experiment by giving w ... [AIP Conf. Proc. 1179, 309 (2009)] published Thu Nov 12, 2009.
Natural Mode Entanglement as a Resource for Quantum Communication
Libby Heaney and Vlatko Vedral
Natural particle-number entanglement resides between spatial modes in coherent ultracold atomic gases. However, operations on the modes are restricted by a superselection rule that forbids coherent superpositions of different particle numbers. This seemingly prevents mode entanglement being used as ... [Phys. Rev. Lett. 103, 200502 (2009)] published Wed Nov 11, 2009.
Gaussian-state quantum-illumination receivers for target detection
Saikat Guha and Baris I. Erkmen
The signal half of an entangled twin beam, generated using spontaneous parametric downconversion, interrogates a region of space that is suspected of containing a target and has high loss and high (entanglement-breaking) background noise. A joint measurement is performed on the returned light and th ... [Phys. Rev. A 80, 052310 (2009)] published Tue Nov 10, 2009.
High-performance diamond-based single-photon sources for quantum communication
Chun-Hsu Su, Andrew D. Greentree, and Lloyd C. L. Hollenberg
Quantum communication places stringent requirements on single-photon sources. Here we report a theoretical study of the cavity Purcell enhancement of two diamond point defects, the nickel-nitrogen (NE8) and silicon-vacancy (SiV) centers, for high-performance, near on-demand single-photon generation. ... [Phys. Rev. A 80, 052308 (2009)] published Mon Nov 9, 2009.
Long-distance entanglement and quantum teleportation in coupled-cavity arrays
Salvatore M. Giampaolo and Fabrizio Illuminati
We introduce quantum spin models whose ground states allow for sizable entanglement between distant spins. We discuss how spin models with global end-to-end entanglement realize quantum teleportation channels with optimal compromise between scalability and resilience to thermal decoherence and can b ... [Phys. Rev. A 80, 050301 (2009)] published Fri Nov 6, 2009.
Chirped Biphotons and their Compression in Optical Fibers
G. Brida, M. V. Chekhova, I. P. Degiovanni, M. Genovese, G. Kh. Kitaeva et al.
We show that broadband biphoton wave packets produced via sponateous parametric down-conversion in crystals with linearly aperiodic poling can be easily compressed in time using the effect of group-velocity dispersion in optical fibers. This result could foster important developments in quantum metr ... [Phys. Rev. Lett. 103, 193602 (2009)] published Thu Nov 5, 2009.
Forgetfulness of continuous Markovian quantum channels
Cosmo Lupo, Laleh Memarzadeh, and Stefano Mancini
The notion of forgetfulness, used in discrete quantum memory channels, is slightly weakened in order to be applied to the case of continuous channels. This is done in the context of quantum memory channels with Markovian noise. As a case study, we apply the notion of weak forgetfulness to a bosonic ... [Phys. Rev. A 80, 042328 (2009)] published Tue Oct 27, 2009.
Geometry of generalized depolarizing channels
Christian K. Burrell
A generalized depolarizing channel acts on an N-dimensional quantum system to compress the Bloch ball in N1 directions; it has a corresponding compression vector. We investigate the geometry of these compression vectors and prove a conjecture of Dixit and Sudarshan [Phys. Rev. A 78, 032308 (2008)], ... [Phys. Rev. A 80, 042330 (2009)] published Tue Oct 27, 2009.
Hybrid photonic entanglement: Realization, characterization, and applications
Leonardo Neves, Gustavo Lima, Aldo Delgado, and Carlos Saavedra
We show that the quantum disentanglement eraser implemented on a two-photon system from parametric downconversion is a general method to create hybrid photonic entanglement, namely the entanglement between different degrees of freedom of the photon pair. To demonstrate this, we generate and characte ... [Phys. Rev. A 80, 042322 (2009)] published Thu Oct 22, 2009.
Quantum communication network utilizing quadripartite entangled states of optical field
Heng Shen, Xiaolong Su, Xiaojun Jia, and Changde Xie
We propose two types of quantum dense coding communication networks with optical continuous variables, in which a quadripartite entangled state of the optical field with totally three-party correlations of quadrature amplitudes is utilized. In the networks, the exchange of information between any tw ... [Phys. Rev. A 80, 042320 (2009)] published Thu Oct 22, 2009.
Unconditional Security of Single-Photon Differential Phase Shift Quantum Key Distribution
Kai Wen, Kiyoshi Tamaki, and Yoshihisa Yamamoto
In this Letter, we prove the unconditional security of the single-photon differential phase shift quantum key distribution (DPS-QKD) protocol, based on the conversion to an equivalent entanglement-based protocol. We estimate the upper bound of the phase error rate from the bit error rate, and show t ... [Phys. Rev. Lett. 103, 170503 (2009)] published Thu Oct 22, 2009.
Can Closed Timelike Curves or Nonlinear Quantum Mechanics Improve Quantum State Discrimination or Help Solve Hard Problems?
Charles H. Bennett, Debbie Leung, Graeme Smith, and John A. Smolin
We study the power of closed timelike curves (CTCs) and other nonlinear extensions of quantum mechanics for distinguishing nonorthogonal states and speeding up hard computations. If a CTC-assisted computer is presented with a labeled mixture of states to be distinguishedthe most natural formulationw ... [Phys. Rev. Lett. 103, 170502 (2009)] published Wed Oct 21, 2009.
Universal existence of exact quantum state transmissions in interacting media
Lian-Ao Wu, Yu-xi Liu, and Franco Nori
We consider an exact state transmission, where a density matrix in one information processor A at time t=0 is exactly equal to that in another processor B at a later time. We demonstrate that there always exists a complete set of orthogonal states, which can be employed to perform the exact state tr ... [Phys. Rev. A 80, 042315 (2009)] published Mon Oct 19, 2009.
Erratum: Linear optical protocol for preparation of N-photon GreenbergerHorneZeilinger state with conventional photon detectors [Appl. Phys. Lett. 92, 021127 (2008)]
Yan Xia, Jie Song, and He-Shan Song
Abstract not available. [Appl. Phys. Lett. 95, 169901 (2009)] published Mon Oct 19, 2009.
Rising time of entanglement between scattering spins
Francesco Ciccarello, Mauro Paternostro, G. Massimo Palma, and Michelangelo Zarcone
We investigate the time evolution of entanglement in a process where a mobile particle is scattered by static spins. We show that entanglement increases monotonically during a transient and then saturates to a steady-state value. For a quasimonochromatic mobile particle, the transient time depends o ... [Phys. Rev. B 80, 165313 (2009)] published Fri Oct 9, 2009.
Entanglement purification with double selection
Keisuke Fujii and Katsuji Yamamoto
We investigate an entanglement purification protocol with double-selection process, which works under imperfect local operations. Compared with the usual protocol with single selection, this double-selection method has higher noise thresholds for the local operations and quantum communication channe ... [Phys. Rev. A 80, 042308 (2009)] published Fri Oct 9, 2009.