PRA: Quantum information

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Recently published articles in Phys. Rev. A in the Table of Content section "Quantum information"
Updated: 36 min 35 sec ago

Symmetrizing cost of quantum states

Mon, 2017-03-27 16:00

Author(s): Eyuri Wakakuwa

We introduce and analyze a task that we call symmetrization, in which a state of a quantum system, associated with a symmetry group, is transformed by a random unitary operation to a symmetric state. Each element of the unitary ensemble is required to be symmetry preserving, in the sense that it kee…


[Phys. Rev. A 95, 032328] Published Mon Mar 27, 2017

Categories: Journals, Physics

Loss-tolerant parity measurement for distant quantum bits

Mon, 2017-03-27 16:00

Author(s): Alain Sarlette and Mazyar Mirrahimi

We propose a scheme to measure the parity of two distant qubits, while ensuring that losses on the quantum channel between them does not destroy coherences within the parity subspaces. This capability enables deterministic preparation of highly entangled qubit states whose fidelity is not limited by…


[Phys. Rev. A 95, 032329] Published Mon Mar 27, 2017

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Equivalence between spin Hamiltonians and boson sampling

Fri, 2017-03-24 16:00

Author(s): Borja Peropadre, Alán Aspuru-Guzik, and Juan José García-Ripoll

A map between the problems of boson sampling and simulating the evolution of interacting spins is established. By enabling the use of physical systems other than traditional optical circuits as quantum simulators, this work increases the odds of proving quantum supremacy.


[Phys. Rev. A 95, 032327] Published Fri Mar 24, 2017

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Quantum speedup of the traveling-salesman problem for bounded-degree graphs

Wed, 2017-03-22 16:00

Author(s): Dominic J. Moylett, Noah Linden, and Ashley Montanaro

The traveling-salesman problem is an iconic route-finding task, with applications from chip design to planning and logistics. Here the authors show that if the graph of cities to be visited is of low degree, a traveling salesman armed with a quantum satnav can find the best route quadratically faster than using any known classical method.


[Phys. Rev. A 95, 032323] Published Wed Mar 22, 2017

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Topological order and memory time in marginally-self-correcting quantum memory

Wed, 2017-03-22 16:00

Author(s): Karthik Siva and Beni Yoshida

We examine two proposals for marginally-self-correcting quantum memory: the cubic code by Haah and the welded code by Michnicki. In particular, we prove explicitly that they are absent of topological order above zero temperature, as their Gibbs ensembles can be prepared via a short-depth quantum cir…


[Phys. Rev. A 95, 032324] Published Wed Mar 22, 2017

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Measurement-device-independent quantum key distribution with source state errors and statistical fluctuation

Wed, 2017-03-22 16:00

Author(s): Cong Jiang, Zong-Wen Yu, and Xiang-Bin Wang

We show how to calculate the secure final key rate in the four-intensity decoy-state measurement-device-independent quantum key distribution protocol with both source errors and statistical fluctuations with a certain failure probability. Our results rely only on the range of only a few parameters i…


[Phys. Rev. A 95, 032325] Published Wed Mar 22, 2017

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Resolution-enhanced entanglement detection

Wed, 2017-03-22 16:00

Author(s): Manuel Gessner, Luca Pezzè, and Augusto Smerzi

We formulate a general family of entanglement criteria for multipartite states on arbitrary Hilbert spaces. Fisher information criteria compare the sensitivity to unitary rotations with the variances of suitable local observables. Generalized squeezing-type criteria provide lower bounds that are les…


[Phys. Rev. A 95, 032326] Published Wed Mar 22, 2017

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Quantum multiparameter estimation with generalized balanced multimode NOON-like states

Mon, 2017-03-20 16:00

Author(s): Lu Zhang and Kam Wai Clifford Chan

The simultaneous multiparameter estimation problem using a class of multimode entangled states is investigated in this paper. Specifically, the problem of optical phase imaging is considered, and the quantum probe is taken to be a balanced coherent superposition of components with an arbitrary quant…


[Phys. Rev. A 95, 032321] Published Mon Mar 20, 2017

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Generation and characterization of discrete spatial entanglement in multimode nonlinear waveguides

Mon, 2017-03-20 16:00

Author(s): Michał Jachura, Michał Karpiński, Konrad Banaszek, Divya Bharadwaj, Jasleen Lugani, and K. Thyagarajan

We analyze theoretically spontaneous parametric down-conversion in a multimode nonlinear waveguide as a source of entangled pairs of spatial qubits, realized as superpositions of a photon in two orthogonal transverse modes of the waveguide. It is shown that, by exploiting intermodal dispersion, down…


[Phys. Rev. A 95, 032322] Published Mon Mar 20, 2017

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Pareto-front shape in multiobservable quantum control

Fri, 2017-03-17 16:00

Author(s): Qiuyang Sun, Re-Bing Wu, and Herschel Rabitz

Many scenarios in the sciences and engineering require simultaneous optimization of multiple objective functions, which are usually conflicting or competing. In such problems the Pareto front, where none of the individual objectives can be further improved without degrading some others, shows the tr…


[Phys. Rev. A 95, 032319] Published Fri Mar 17, 2017

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Error correction with orbital angular momentum of multiple photons propagating in a turbulent atmosphere

Fri, 2017-03-17 16:00

Author(s): José Raúl González Alonso and Todd A. Brun

Orbital angular momentum of photons is an intriguing system for the storage and transmission of quantum information, but it is rapidly degraded by atmospheric turbulence. Understanding the noise processes that affect photons is essential if we desire to protect them. In this paper we use the infinit…


[Phys. Rev. A 95, 032320] Published Fri Mar 17, 2017

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Reexamination of strong subadditivity: A quantum-correlation approach

Mon, 2017-03-13 16:00

Author(s): Razieh Taghiabadi, Seyed Javad Akhtarshenas, and Mohsen Sarbishaei

The strong subadditivity inequality of von Neumann entropy relates the entropy of subsystems of a tripartite state ρABC to that of the composite system. Here, we define T(a)(ρABC) as the extent to which ρABC fails to satisfy the strong subadditivity inequality S(ρB)+S(ρC)≤S(ρAB)+S(ρAC) with equality…


[Phys. Rev. A 95, 032315] Published Mon Mar 13, 2017

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Fast phase manipulation of the single nuclear spin in solids by rotating fields

Mon, 2017-03-13 16:00

Author(s): T. Shimo-Oka, Y. Tokura, Y. Suzuki, and N. Mizuochi

We propose fast phase gates of single nuclear spins interacting with single electron spins. The gate operation utilizes geometric phase shifts of the electron spin induced by fast and slow rotating fields; the path difference depending on nuclear-spin states enables nuclear phase shifts. The gate ti…


[Phys. Rev. A 95, 032316] Published Mon Mar 13, 2017

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Bacon-Shor code with continuous measurement of noncommuting operators

Mon, 2017-03-13 16:00

Author(s): Juan Atalaya, Mohammad Bahrami, Leonid P. Pryadko, and Alexander N. Korotkov

We analyze the operation of a four-qubit Bacon-Shor code with simultaneous continuous measurement of noncommuting gauge operators. The error syndrome in this case is monitored via time-averaged cross-correlators of the output signals. We find the logical error rate for several models of decoherence,…


[Phys. Rev. A 95, 032317] Published Mon Mar 13, 2017

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Centrality measure based on continuous-time quantum walks and experimental realization

Mon, 2017-03-13 16:00

Author(s): Josh A. Izaac, Xiang Zhan, Zhihao Bian, Kunkun Wang, Jian Li, Jingbo B. Wang, and Peng Xue

Network centrality has important implications well beyond its role in physical and information transport analysis; as such, various quantum-walk-based algorithms have been proposed for measuring network vertex centrality. In this work, we propose a continuous-time quantum walk algorithm for determin…


[Phys. Rev. A 95, 032318] Published Mon Mar 13, 2017

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Quantum annealing with ultracold atoms in a multimode optical resonator

Thu, 2017-03-09 17:00

Author(s): Valentin Torggler, Sebastian Krämer, and Helmut Ritsch

A dilutely filled N-site optical lattice near zero temperature within a high-Q multimode cavity can be mapped to a spin ensemble with tailorable interactions at all length scales. The effective full site to site interaction matrix can be dynamically controlled by the application of up to N(N+1)/2 la…


[Phys. Rev. A 95, 032310] Published Thu Mar 09, 2017

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Qudit quantum computation on matrix product states with global symmetry

Thu, 2017-03-09 17:00

Author(s): Dong-Sheng Wang, David T. Stephen, and Robert Raussendorf

Resource states that contain nontrivial symmetry-protected topological order are identified for universal single-qudit measurement-based quantum computation. Our resource states fall into two classes: one as the qudit generalizations of the one-dimensional qubit cluster state, and the other as the h…


[Phys. Rev. A 95, 032312] Published Thu Mar 09, 2017

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Composite control for protecting two nonorthogonal qubit states against decoherence

Thu, 2017-03-09 17:00

Author(s): Ya Cao, Guojing Tian, Zhi-Chao Zhang, Ying-Hui Yang, Qiao-Yan Wen, and Fei Gao

Quantum feedback control (QFBC) and quantum feedforward control (QFFC) are two of the major techniques for protecting two nonorthogonal qubit states against decoherence. In this paper, we propose a quantum composite control scheme for protecting such states, where QFBC and QFFC are combined. Note th…


[Phys. Rev. A 95, 032313] Published Thu Mar 09, 2017

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Enhancing the fidelity of two-qubit gates by measurements

Thu, 2017-03-09 17:00

Author(s): Tuvia Gefen, Daniel Cohen, Itsik Cohen, and Alex Retzker

Dynamical decoupling techniques are the method of choice for increasing gate fidelities. While these methods have produced very impressive results in terms of decreasing local noise and increasing the fidelities of single-qubit operations, dealing with the noise of two-qubit gates has proven more ch…


[Phys. Rev. A 95, 032314] Published Thu Mar 09, 2017

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Composite nonadiabatic holonomic quantum computation

Wed, 2017-03-08 17:00

Author(s): G. F. Xu, P. Z. Zhao, T. H. Xing, Erik Sjöqvist, and D. M. Tong

Nonadiabatic holonomic quantum computation has a robust feature in suppressing control errors because of its holonomic feature. However, this kind of robust feature is challenged since the usual way of realizing nonadiabatic holonomic gates introduces errors due to systematic errors in the control p…


[Phys. Rev. A 95, 032311] Published Wed Mar 08, 2017

Categories: Journals, Physics