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PRA: Quantum information

Recently published articles in Phys. Rev. A in the Table of Content section "Quantum information"

Published: 2017-12-13T17:02:26+00:00


Steady many-body entanglements in dissipative systems


Author(s): G. D. de Moraes Neto, V. F. Teizen, V. Montenegro, and E. Vernek

We propose a dissipative method for the preparation of many-body steady entangled states in spin and fermionic chains. The scheme is accomplished by means of an engineered set of Lindbladians acting over the eigenmodes of the system, whose spectrum is assumed to be resolvable. We apply this idea to ...

[Phys. Rev. A 96, 062313] Published Wed Dec 13, 2017

Evolution of entanglement under an Ising-like Hamiltonian with particle losses


Author(s): Konrad Szymański and Krzysztof Pawłowski

We present an analytical compact solution for the density matrix and all correlation functions of two collective-macroscopic spins evolving via an Ising-like Hamiltonian in the presence of particle losses. The losses introduce nonlocal phase noise which destroys highly entangled states arising in th...

[Phys. Rev. A 96, 062312] Published Tue Dec 12, 2017

Detecting Gaussian entanglement via extractable work


Author(s): Matteo Brunelli, Marco G. Genoni, Marco Barbieri, and Mauro Paternostro

We show how the presence of entanglement in a bipartite Gaussian state can be detected by the amount of work extracted by a continuous-variable Szilard-like device, where the bipartite state serves as the working medium of the engine. We provide an expression for the work extracted in such a process...

[Phys. Rev. A 96, 062311] Published Mon Dec 11, 2017

Symmetric three-qubit-state invariants


Author(s): Alexander Meill and David A. Meyer

For pure symmetric three-qubit states there are only three algebraically independent entanglement measures; one choice is the pairwise concurrence $\mathcal{C}$, the three-tangle $τ$, and the Kempe invariant $κ$. Using a canonical form for symmetric $n$-qubit states derived from their Majorana repre...

[Phys. Rev. A 96, 062310] Published Fri Dec 08, 2017

Continuous-variable quantum key distribution with a leakage from state preparation


Author(s): Ivan Derkach, Vladyslav C. Usenko, and Radim Filip

We address side-channel leakage in a trusted preparation station of continuous-variable quantum key distribution with coherent and squeezed states. We consider two different scenarios: multimode Gaussian modulation, directly accessible to an eavesdropper, or side-channel loss of the signal states pr...

[Phys. Rev. A 96, 062309] Published Thu Dec 07, 2017

Triangle inequalities in coherence measures and entanglement concurrence


Author(s): Yue Dai, Wenlong You, Yuli Dong, and Chengjie Zhang

We provide detailed proofs of triangle inequalities in coherence measures and entanglement concurrence. If a rank-2 state $ϱ$ can be expressed as a convex combination of two pure states, i.e., $ϱ={p}_{1}|{ψ}_{1}〉〈{ψ}_{1}|+{p}_{2}|{ψ}_{2}〉〈{ψ}_{2}|$, a triangle inequality can be established as $|E(|{...

[Phys. Rev. A 96, 062308] Published Wed Dec 06, 2017

Continuous-variable sampling from photon-added or photon-subtracted squeezed states


Author(s): U. Chabaud, T. Douce, D. Markham, P. van Loock, E. Kashefi, and G. Ferrini

We introduce a family of quantum circuits in continuous variables and we show that, relying on the widely accepted conjecture that the polynomial hierarchy of complexity classes does not collapse, their output probability distribution cannot be efficiently simulated by a classical computer. These ci...

[Phys. Rev. A 96, 062307] Published Tue Dec 05, 2017

Practical resources and measurements for lossy optical quantum metrology


Author(s): Changhun Oh, Su-Yong Lee, Hyunchul Nha, and Hyunseok Jeong

We study the sensitivity of phase estimation in a lossy Mach-Zehnder interferometer (MZI) using two general, and practical, resources generated by a laser and a nonlinear optical medium with passive optimal elements, which are readily available in the laboratory: One is a two-mode separable coherent...

[Phys. Rev. A 96, 062304] Published Mon Dec 04, 2017

Reliable computation from contextual correlations


Author(s): André L. Oestereich and Ernesto F. Galvão

An operational approach to the study of computation based on correlations considers black boxes with one-bit inputs and outputs, controlled by a limited classical computer capable only of performing sums modulo-two. In this setting, it was shown that noncontextual correlations do not provide any ext...

[Phys. Rev. A 96, 062305] Published Mon Dec 04, 2017

Bounding the quantum limits of precision for phase estimation with loss and thermal noise


Author(s): Christos N. Gagatsos, Boulat A. Bash, Saikat Guha, and Animesh Datta

We consider the problem of estimating an unknown but constant carrier phase modulation $θ$ using a general, possibly entangled, $n$-mode optical probe through $n$ independent and identical uses of a lossy bosonic channel with additive thermal noise. We find an upper bound to the quantum Fisher infor...

[Phys. Rev. A 96, 062306] Published Mon Dec 04, 2017

Quantum interface between a transmon qubit and spins of nitrogen-vacancy centers


Author(s): Yaowen Hu, Yipu Song, and Luming Duan

Hybrid quantum circuits combining advantages of each individual system have provided a promising platform for quantum information processing. Here we propose an experimental scheme to directly couple a transmon qubit to an individual spin in the nitrogen-vacancy (NV) center, with a coupling strength...

[Phys. Rev. A 96, 062301] Published Fri Dec 01, 2017

Gate-error analysis in simulations of quantum computers with transmon qubits


Author(s): D. Willsch, M. Nocon, F. Jin, H. De Raedt, and K. Michielsen

Usual metrics, such as the fidelity, used to characterize the success of implementing superconducting qubit-based quantum gates are analyzed. By numerically solving time-dependent Schrödinger equations for a transmon system, it is found that such metrics are not reliable to predict the performance of a quantum algorithm when the gates are used repeatedly.

[Phys. Rev. A 96, 062302] Published Fri Dec 01, 2017

Quantum simulation of quantum channels in nuclear magnetic resonance


Author(s): Tao Xin, Shi-Jie Wei, Julen S. Pedernales, Enrique Solano, and Gui-Lu Long

We propose and experimentally demonstrate an efficient framework for the quantum simulation of quantum channels in nuclear magnetic resonance (NMR). Our approach relies on the suitable decomposition of nonunitary operators in a linear combination of $d$ unitary ones, which can be then experimentally...

[Phys. Rev. A 96, 062303] Published Fri Dec 01, 2017

Obtaining better performance in the measurement-device-independent quantum key distribution with heralded single-photon sources


Author(s): Xing-Yu Zhou, Chun-Hui Zhang, Chun-Mei Zhang, and Qin Wang

Measurement-device-independent quantum key distribution (MDI-QKD) has been widely investigated due to its remarkable advantages on the achievable transmission distance and practical security. However, the relative low key generation rate limits its real-life implementations. In this work, we adopt t...

[Phys. Rev. A 96, 052337] Published Tue Nov 28, 2017

Polarization entanglement purification of nonlocal microwave photons based on the cross-Kerr effect in circuit QED


Author(s): Hao Zhang (张浩), Qian Liu (刘倩), Xu-Sheng Xu (徐旭升), Jun Xiong (熊俊), Ahmed Alsaedi, Tasawar Hayat, and Fu-Guo Deng (邓富国)

Microwave photons have become very important qubits in quantum communication, as the first quantum satellite has been launched successfully. Therefore, it is a necessary and meaningful task for ensuring the high security and efficiency of microwave-based quantum communication in practice. Here, we p...

[Phys. Rev. A 96, 052330] Published Mon Nov 27, 2017

Building mechanical Greenberger-Horne-Zeilinger and cluster states by harnessing optomechanical quantum steerable correlations


Author(s): Huatang Tan, Yanghua Wei, and Gaoxiang Li

Greenberger-Horne-Zeilinger (GHZ) and cluster states are two typical kinds of multipartite entangled states and can respectively be used for realizing quantum networks and one-way computation. We propose a feasible scheme for generating Gaussian GHZ and cluster states of multiple mechanical oscillat...

[Phys. Rev. A 96, 052331] Published Mon Nov 27, 2017

Measure-independent anomaly of nonlocality


Author(s): S. Camalet

We show that any Bell local state with a hidden nonlocality that can be revealed by local filtering is more, or equally, entangled than nonlocal states. More precisely, it can be deterministically transformed into a nonlocal state by local operations and classical communication. For such a state, th...

[Phys. Rev. A 96, 052332] Published Mon Nov 27, 2017

Computing on quantum shared secrets


Author(s): Yingkai Ouyang, Si-Hui Tan, Liming Zhao, and Joseph F. Fitzsimons

A ($k,n$)-threshold secret-sharing scheme allows for a string to be split into $n$ shares in such a way that any subset of at least $k$ shares suffices to recover the secret string, but such that any subset of at most $k−1$ shares contains no information about the secret. Quantum secret-sharing sche...

[Phys. Rev. A 96, 052333] Published Mon Nov 27, 2017

Lieb-Robinson bounds on $n$-partite connected correlation functions


Author(s): Minh Cong Tran, James R. Garrison, Zhe-Xuan Gong, and Alexey V. Gorshkov

Lieb and Robinson provided bounds on how fast bipartite connected correlations can arise in systems with only short-range interactions. We generalize Lieb-Robinson bounds on bipartite connected correlators to multipartite connected correlators. The bounds imply that an $n$-partite connected correlat...

[Phys. Rev. A 96, 052334] Published Mon Nov 27, 2017

Counterfactual quantum cloning without transmitting any physical particles


Author(s): Qi Guo, Shuqin Zhai, Liu-Yong Cheng, Hong-Fu Wang, and Shou Zhang

We propose a counterfactual $1→2$ economical phase-covariant cloning scheme. Compared with the existing protocols using flying qubits, the main difference of the presented scheme is that the cloning can be achieved without transmitting the photon between the two parties. In addition, this counterfac...

[Phys. Rev. A 96, 052335] Published Mon Nov 27, 2017

Logarithmic coherence: Operational interpretation of ${ℓ}_{1}$-norm coherence


Author(s): Swapan Rana, Preeti Parashar, Andreas Winter, and Maciej Lewenstein

We show that the distillable coherence—which is equal to the relative entropy of coherence—is, up to a constant factor, always bounded by the ${ℓ}_{1}$-norm measure of coherence (defined as the sum of absolute values of off diagonals). Thus the latter plays a similar role as logarithmic negativity p...

[Phys. Rev. A 96, 052336] Published Mon Nov 27, 2017

Suppression of effective noise in Hamiltonian simulations


Author(s): Milad Marvian, Todd A. Brun, and Daniel A. Lidar

Simulating high-weight Hamiltonians can convert local noise on the original Hamiltonian into undesirable nonlocal noise on the simulated Hamiltonian. Here we show how, starting from a two-local Hamiltonian in the presence of non-Markovian noise, a desired computation can be simulated as well as prot...

[Phys. Rev. A 96, 052328] Published Wed Nov 22, 2017

Hybrid quantum repeater based on resonant qubit-field interactions


Author(s): József Zsolt Bernád

We propose a hybrid quantum repeater based on ancillary coherent field states and material qubits coupled to optical cavities. For this purpose, resonant qubit-field interactions and postselective field measurements are determined which are capable of realizing all necessary two-qubit operations for...

[Phys. Rev. A 96, 052329] Published Wed Nov 22, 2017

Finite sizes and smooth cutoffs in superconducting circuits


Author(s): Emma McKay, Adrian Lupascu, and Eduardo Martín-Martínez

We investigate the validity of two common assumptions in the modeling of superconducting circuits: first, that the superconducting qubits are pointlike and, second, that the UV behavior of the transmission line is not relevant to the qubit dynamics. We show that in the experimentally accessible ultr...

[Phys. Rev. A 96, 052325] Published Mon Nov 20, 2017

Tighter Einstein-Podolsky-Rosen steering inequality based on the sum-uncertainty relation


Author(s): Ananda G. Maity, Shounak Datta, and A. S. Majumdar

We consider the uncertainty bound on the sum of variances of two incompatible observables in order to derive a corresponding steering inequality. Our steering criterion, when applied to discrete variables, yields the optimum steering range for two-qubit Werner states in the two-measurement and two-o...

[Phys. Rev. A 96, 052326] Published Mon Nov 20, 2017

Capability of local operations and classical communication to distinguish bipartite unitary operations


Author(s): Lvzhou Li, Shenggen Zheng, Haozhen Situ, and Daowen Qiu

The problem studied in this paper is, if the number of queries to unitary operations is fixed, say $k$, then when do local operations and classical communication (LOCC) suffice for optimally distinguishing bipartite unitary operations? We consider the above problem for two-qubit unitary operations i...

[Phys. Rev. A 96, 052327] Published Mon Nov 20, 2017

Vacuum spin squeezing


Author(s): Jiazhong Hu, Wenlan Chen, Zachary Vendeiro, Alban Urvoy, Boris Braverman, and Vladan Vuletić

We investigate the generation of entanglement (spin squeezing) in an optical-transition atomic clock through the coupling to an optical cavity in its vacuum state. We show that if each atom is prepared in a superposition of the ground state and a long-lived electronic excited state, and viewed as a ...

[Phys. Rev. A 96, 050301(R)] Published Thu Nov 16, 2017

Interpreting quantum coherence through a quantum measurement process


Author(s): Yao Yao, G. H. Dong, Xing Xiao, Mo Li, and C. P. Sun

Recently, there has been a renewed interest in the quantification of coherence or other coherencelike concepts within the framework of quantum resource theory. However, rigorously defined or not, the notion of coherence or decoherence has already been used by the community for decades since the adve...

[Phys. Rev. A 96, 052322] Published Thu Nov 16, 2017

Witnessing arbitrary bipartite entanglement in a measurement-device-independent way


Author(s): Arindam Mallick and Sibasish Ghosh

Experimental detection of entanglement of an arbitrary state of a given bipartite system is crucial for exploring many areas of quantum information processing. But such a detection should be made in a device-independent way if the preparation process of the state is considered to be faithful, in ord...

[Phys. Rev. A 96, 052323] Published Thu Nov 16, 2017

Quantifying non-Gaussianity of quantum-state correlation


Author(s): Jiyong Park, Jaehak Lee, Se-Wan Ji, and Hyunchul Nha

We consider how to quantify non-Gaussianity for the correlation of a bipartite quantum state by using various measures such as relative entropy and geometric distances. We first show that an intuitive approach, i.e., subtracting the correlation of a reference Gaussian state from that of a target non...

[Phys. Rev. A 96, 052324] Published Thu Nov 16, 2017

Enhancing qubit readout through dissipative sub-Poissonian dynamics


Author(s): B. D'Anjou and W. A. Coish

Single-shot qubit readout typically combines high readout contrast with long-lived readout signals, leading to large signal-to-noise ratios and high readout fidelities. In recent years, it has been demonstrated that both readout contrast and readout signal lifetime, and thus the signal-to-noise rati...

[Phys. Rev. A 96, 052321] Published Wed Nov 15, 2017

Broadcasting quantum coherence via cloning


Author(s): Udit Kamal Sharma, Indranil Chakrabarty, and Manish Kumar Shukla

Quantum coherence has recently emerged as a key candidate for use as a resource in various quantum information processing tasks. Therefore, it is of utmost importance to explore the possibility of creating a greater number of coherent states from an existing coherent pair. In other words, we start w...

[Phys. Rev. A 96, 052319] Published Tue Nov 14, 2017

Blueprint for fault-tolerant quantum computation with Rydberg atoms


Author(s): James M. Auger, Silvia Bergamini, and Dan E. Browne

We present a blueprint for building a fault-tolerant universal quantum computer with Rydberg atoms. Our scheme, which is based on the surface code, uses individually addressable, optically trapped atoms as qubits and exploits electromagnetically induced transparency to perform the multiqubit gates r...

[Phys. Rev. A 96, 052320] Published Tue Nov 14, 2017

Memory-assisted quantum key distribution with a single nitrogen-vacancy center


Author(s): Nicoló Lo Piparo, Mohsen Razavi, and William J. Munro

Memory-assisted measurement-device-independent quantum key distribution (MA-MDI-QKD) is a promising scheme that aims to improve the rate-versus-distance behavior of a QKD system by using the state-of-the-art devices. It can be seen as a bridge between current QKD links to quantum repeater based netw...

[Phys. Rev. A 96, 052313] Published Mon Nov 13, 2017

Measure and detection of genuine multipartite entanglement for tripartite systems


Author(s): Ming Li, Lingxia Jia, Jing Wang, Shuqian Shen, and Shao-Ming Fei

It is a computationally hard task to certify genuine multipartite entanglement (GME). We investigate the relation between the norms of the correlation vectors and the detection of GME for tripartite quantum systems. A sufficient condition for GME and an effective lower bound for the GME concurrence ...

[Phys. Rev. A 96, 052314] Published Mon Nov 13, 2017

Quantum computation with indefinite causal structures


Author(s): Mateus Araújo, Philippe Allard Guérin, and Ämin Baumeler

One way to study the physical plausibility of closed timelike curves (CTCs) is to examine their computational power. This has been done for Deutschian CTCs (D-CTCs) and postselection CTCs (P-CTCs), with the result that they allow for the efficient solution of problems in PSPACE and PP, respectively....

[Phys. Rev. A 96, 052315] Published Mon Nov 13, 2017

Rydberg-atom-based scheme of nonadiabatic geometric quantum computation


Author(s): P. Z. Zhao, Xiao-Dan Cui, G. F. Xu, Erik Sjöqvist, and D. M. Tong

Nonadiabatic geometric quantum computation provides a means to perform fast and robust quantum gates. It has been implemented in various physical systems, such as trapped ions, nuclear magnetic resonance, and superconducting circuits. Another system being adequate for implementation of nonadiabatic ...

[Phys. Rev. A 96, 052316] Published Mon Nov 13, 2017

Universal controlled-phase gate with cat-state qubits in circuit QED


Author(s): Yu Zhang, Xiong Zhao, Zhen-Fei Zheng, Li Yu, Qi-Ping Su, and Chui-Ping Yang

Cat-state qubits (qubits encoded with cat states) have recently drawn intensive attention due to their enhanced lifetimes with quantum error correction. We here propose a method to implement a universal controlled-phase gate of two cat-state qubits via two microwave resonators coupled to a supercond...

[Phys. Rev. A 96, 052317] Published Mon Nov 13, 2017

Universal superposition of orthogonal states


Author(s): Mina Doosti, Farzad Kianvash, and Vahid Karimipour

It is known that no quantum process can produce a predetermined superposition of unknown arbitrary states. It has already been shown that with some partial information about the states, one can produce with some probability such superpositions. In general the success probability of these machines, e...

[Phys. Rev. A 96, 052318] Published Mon Nov 13, 2017

Atom-field entanglement in cavity QED: Nonlinearity and saturation


Author(s): Robert Rogers, Nick Cummings, Leno M. Pedrotti, and Perry Rice

We investigate the degree of entanglement between an atom and a driven cavity mode in the presence of dissipation. Previous work has shown that in the limit of weak driving fields, the steady-state entanglement is proportional to the square of the driving intensity. This quadratic dependence is due ...

[Phys. Rev. A 96, 052311] Published Wed Nov 08, 2017

Reconstructing quantum states from single-party information


Author(s): Christian Schilling, Carlos L. Benavides-Riveros, and Péter Vrana

The possible compatibility of density matrices for single-party subsystems is described by linear constraints on their respective spectra. Whenever some of those quantum marginal constraints are saturated, the total quantum state has a specific, simplified structure. We prove that these remarkable g...

[Phys. Rev. A 96, 052312] Published Wed Nov 08, 2017

Self-guided method to search maximal Bell violations for unknown quantum states


Author(s): Li-Kai Yang, Geng Chen, Wen-Hao Zhang, Xing-Xiang Peng, Shang Yu, Xiang-Jun Ye, Chuan-Feng Li, and Guang-Can Guo

In recent decades, a great variety of research and applications concerning Bell nonlocality have been developed with the advent of quantum information science. Providing that Bell nonlocality can be revealed by the violation of a family of Bell inequalities, finding maximal Bell violation (MBV) for ...

[Phys. Rev. A 96, 052310] Published Tue Nov 07, 2017

Finding resource states of measurement-based quantum computing is harder than quantum computing


Author(s): Tomoyuki Morimae

Measurement-based quantum computing enables universal quantum computing with only adaptive single-qubit measurements on certain many-qubit states, such as the graph state, the Affleck-Kennedy-Lieb-Tasaki (AKLT) state, and several tensor-network states. Finding new resource states of measurement-base...

[Phys. Rev. A 96, 052308] Published Mon Nov 06, 2017

Maximum coherence in the optimal basis


Author(s): Ming-Liang Hu, Shu-Qian Shen, and Heng Fan

The resource theoretic measure of quantum coherence is basis dependent, and the amount of coherence contained in a state is different in different bases. We obtained analytical solutions for the maximum coherence by optimizing the reference basis and highlighted the essential role of the mutually un...

[Phys. Rev. A 96, 052309] Published Mon Nov 06, 2017

Optimization by a quantum reinforcement algorithm


Author(s): A. Ramezanpour

A reinforcement algorithm solves a classical optimization problem by introducing a feedback to the system, which slowly changes the energy landscape and converges the algorithm to an optimal solution in the configuration space. Here, we use this strategy to concentrate (localize) the wave function o...

[Phys. Rev. A 96, 052307] Published Fri Nov 03, 2017

Magnetic quantum correlations in the one-dimensional transverse-field $XXZ$ model


Author(s): Salimeh Mahdavifar, Saeed Mahdavifar, and R. Jafari

One-dimensional spin-$\frac{1}{2}$ systems are well-known candidates to study the quantum correlations between particles. In condensed matter physics, studies often are restricted to first-neighbor particles. In this work, we consider the one-dimensional $XXZ$ model in a transverse magnetic field (T...

[Phys. Rev. A 96, 052303] Published Thu Nov 02, 2017

Purification of photon subtraction from continuous squeezed light by filtering


Author(s): Jun-ichi Yoshikawa, Warit Asavanant, and Akira Furusawa

Photon subtraction from squeezed states is a powerful scheme to create good approximation of so-called Schrödinger cat states. However, conventional continuous-wave-based methods actually involve some impurity in squeezing of localized wave packets, even in the ideal case of no optical losses. Here,...

[Phys. Rev. A 96, 052304] Published Thu Nov 02, 2017

Protocol for fermionic positive-operator-valued measures


Author(s): D. R. M. Arvidsson-Shukur, H. V. Lepage, E. T. Owen, T. Ferrus, and C. H. W. Barnes

In this paper we present a protocol for the implementation of a positive-operator-valued measure (POVM) on massive fermionic qubits. We present methods for implementing nondispersive qubit transport, spin rotations, and spin polarizing beam-splitter operations. Our scheme attains linear opticslike c...

[Phys. Rev. A 96, 052305] Published Thu Nov 02, 2017

Multiparameter estimation along quantum trajectories with sequential Monte Carlo methods


Author(s): Jason F. Ralph, Simon Maskell, and Kurt Jacobs

This paper proposes an efficient method for the simultaneous estimation of the state of a quantum system and the classical parameters that govern its evolution. This hybrid approach benefits from efficient numerical methods for the integration of stochastic master equations for the quantum system, a...

[Phys. Rev. A 96, 052306] Published Thu Nov 02, 2017

Preservation of quantum coherence under Lorentz boost for narrow uncertainty wave packets


Author(s): Riddhi Chatterjee and A. S. Majumdar

We consider the effect of relativistic boosts on single-particle Gaussian wave packets. The coherence of the wave function as measured by the boosted observer is studied as a function of the momentum and the boost parameter. Using various formulations of coherence, it is shown that in general the co...

[Phys. Rev. A 96, 052301] Published Wed Nov 01, 2017

Multipartite analysis of average-subsystem entropies


Author(s): Ana Alonso-Serrano and Matt Visser

So-called average subsystem entropies are defined by first taking partial traces over some pure state to define density matrices, then calculating the subsystem entropies, and finally averaging over the pure states to define the average subsystem entropies. These quantities are standard tools in qua...

[Phys. Rev. A 96, 052302] Published Wed Nov 01, 2017

Single qubit operations using microwave hyperbolic secant pulses


Author(s): H. S. Ku, J. L. Long, X. Wu, M. Bal, R. E. Lake, Edwin Barnes, Sophia E. Economou, and D. P. Pappas

It has been known since the early days of quantum mechanics that hyperbolic secant pulses possess the unique property that they can perform full-cycle Rabi oscillations on two-level quantum systems independently of the pulse detuning. More recently, it was realized that they induce detuning-controll...

[Phys. Rev. A 96, 042339] Published Mon Oct 30, 2017

Strong quantum solutions in conflicting-interest Bayesian games


Author(s): Ashutosh Rai and Goutam Paul

Quantum entanglement has been recently demonstrated as a useful resource in conflicting-interest games of incomplete information between two players, Alice and Bob [Pappa et al., Phys. Rev. Lett. 114, 020401 (2015)]. The general setting for such games is that of correlated strategies where the corr...

[Phys. Rev. A 96, 042340] Published Mon Oct 30, 2017

Unified framework to determine Gaussian states in continuous-variable systems


Author(s): Fernando Nicacio, Andrea Valdés-Hernández, Ana P. Majtey, and Fabricio Toscano

Gaussian states are the backbone of quantum information protocols with continuous-variable systems whose power relies fundamentally on the entanglement between the different modes. In the case of global pure states, knowledge of the reduced states in a given bipartition of a multipartite quantum sys...

[Phys. Rev. A 96, 042341] Published Mon Oct 30, 2017

Classical simulation of arbitrary quantum noise


Author(s): Seyyed M. H. Halataei

I present an explicit classical simulation of arbitrary quantum noise for quantum models in which one qubit interacts with a quantum bath. The classical model simulates the interaction of the bath and the qubit by random unitary evolutions. I show that any arbitrary quantum dynamics, including quant...

[Phys. Rev. A 96, 042338] Published Fri Oct 27, 2017

Sequentially generated entanglement, macroscopicity, and squeezing in a spin chain


Author(s): Tahereh Abad, Klaus Mølmer, and Vahid Karimipour

We study quantum states generated by a sequence of nearest neighbor bipartite entangling operations along a one-dimensional chain of spin qubits. After a single sweep of such a set of operations, the system is effectively described by a matrix product state (MPS) with the same virtual dimension as t...

[Phys. Rev. A 96, 042337] Published Thu Oct 26, 2017

Progress toward optimal quantum tomography with unbalanced homodyning


Author(s): Y. S. Teo, H. Jeong, and L. L. Sánchez-Soto

Balanced homodyning, heterodyning, and unbalanced homodyning are three well-known sampling techniques used in quantum optics to characterize photonic sources in the continuous-variable regime. We show that for all quantum states and all observable-parameter tomography schemes, which includes reconst...

[Phys. Rev. A 96, 042333] Published Wed Oct 25, 2017

Finite-size analysis of continuous-variable measurement-device-independent quantum key distribution


Author(s): Xueying Zhang, Yichen Zhang, Yijia Zhao, Xiangyu Wang, Song Yu, and Hong Guo

We study the impact of the finite-size effect on the continuous-variable measurement-device-independent quantum key distribution (CV-MDI QKD) protocol, mainly considering the finite-size effect on the parameter estimation procedure. The central-limit theorem and maximum likelihood estimation theorem...

[Phys. Rev. A 96, 042334] Published Wed Oct 25, 2017

Applications of the modified Rydberg antiblockade regime with simultaneous driving


Author(s): Shi-Lei Su, Yongzhi Tian, H. Z. Shen, Huaping Zang, Erjun Liang, and Shou Zhang

Through analyzing the effective dynamics of two Rydberg atoms under the dispersive coupling process, we give a method to modify the traditional antiblockade regime with simultaneous driving without adding any extra controls and resources. The modified regime can be used to construct controlled-PHASE...

[Phys. Rev. A 96, 042335] Published Wed Oct 25, 2017

Coherence number as a discrete quantum resource


Author(s): Seungbeom Chin

We introduce a discrete coherence monotone named the coherence number, which is a generalization of the coherence rank to mixed states. After defining the coherence number in a manner similar to that of the Schmidt number in entanglement theory, we present a necessary and sufficient condition of the...

[Phys. Rev. A 96, 042336] Published Wed Oct 25, 2017

Path-integral quantum Monte Carlo simulation with open-boundary conditions


Author(s): Zhang Jiang, Vadim N. Smelyanskiy, Sergio Boixo, and Hartmut Neven

The tunneling decay event of a metastable state in a fully connected quantum spin model can be simulated efficiently by path-integral quantum Monte Carlo (QMC) [Isakov et al., Phys. Rev. Lett. 117, 180402 (2016)]. This is because the exponential scaling with the number of spins of the thermally ass...

[Phys. Rev. A 96, 042330] Published Mon Oct 23, 2017

Continuous-variable steering and incompatibility via state-channel duality


Author(s): Jukka Kiukas, Costantino Budroni, Roope Uola, and Juha-Pekka Pellonpää

The term Einstein-Podolsky-Rosen steering refers to a quantum correlation intermediate between entanglement and Bell nonlocality, which has been connected to another fundamental quantum property: measurement incompatibility. In the finite-dimensional case, efficient computational methods to quantify...

[Phys. Rev. A 96, 042331] Published Mon Oct 23, 2017

Finite-size analysis of measurement-device-independent quantum cryptography with continuous variables


Author(s): Panagiotis Papanastasiou, Carlo Ottaviani, and Stefano Pirandola

We study the impact of finite-size effects on the key rate of continuous-variable (CV) measurement-device-independent (MDI) quantum key distribution (QKD), considering two-mode Gaussian attacks. Inspired by the parameter estimation technique developed in by Ruppert et al. [Phys. Rev. A 90, 062310 (2...

[Phys. Rev. A 96, 042332] Published Mon Oct 23, 2017

Digital quantum simulator in the presence of a bath


Author(s): Yi-Cong Zheng and Hui-Khoon Ng

For a digital quantum simulator (DQS) imitating a target system, we ask the following question: Under what conditions is the simulator dynamics similar to that of the target in the presence of coupling to a bath? In this paper, we derive conditions for close simulation for three different physical r...

[Phys. Rev. A 96, 042329] Published Fri Oct 20, 2017

Detecting metrologically useful asymmetry and entanglement by a few local measurements


Author(s): Chao Zhang, Benjamin Yadin, Zhi-Bo Hou, Huan Cao, Bi-Heng Liu, Yun-Feng Huang, Reevu Maity, Vlatko Vedral, Chuan-Feng Li, Guang-Can Guo, and Davide Girolami

Important properties of a quantum system are not directly measurable, but they can be disclosed by how fast the system changes under controlled perturbations. In particular, asymmetry and entanglement can be verified by reconstructing the state of a quantum system. Yet, this usually requires experim...

[Phys. Rev. A 96, 042327] Published Thu Oct 19, 2017

Better bounds on optimal measurement and entanglement recovery, with applications to uncertainty and monogamy relations


Author(s): Joseph M. Renes

We extend the recent bounds of Sason and Verdú relating Rényi entropy and Bayesian hypothesis testing (arXiv:1701.01974.) to the quantum domain and show that they have a number of different applications. First, we obtain a sharper bound relating the optimal probability of correctly distinguishing el...

[Phys. Rev. A 96, 042328] Published Thu Oct 19, 2017

Optimal convex approximations of quantum states


Author(s): Massimiliano F. Sacchi

We consider the problem of optimally approximating an unavailable quantum state $ρ$ by the convex mixing of states drawn from a set of available states ${{ν}_{i}}$. The problem is recast to look for the least distinguishable state from $ρ$ among the convex set ${∑}_{i}{p}_{i}{ν}_{i}$, and the corres...

[Phys. Rev. A 96, 042325] Published Wed Oct 18, 2017

Investigating Einstein-Podolsky-Rosen steering of continuous-variable bipartite states by non-Gaussian pseudospin measurements


Author(s): Yu Xiang, Buqing Xu, Ladislav Mišta, Jr., Tommaso Tufarelli, Qiongyi He, and Gerardo Adesso

Einstein-Podolsky-Rosen (EPR) steering is an asymmetric form of correlations which is intermediate between quantum entanglement and Bell nonlocality, and can be exploited as a resource for quantum communication with one untrusted party. In particular, steering of continuous-variable Gaussian states ...

[Phys. Rev. A 96, 042326] Published Wed Oct 18, 2017

Entanglement-enhanced lidars for simultaneous range and velocity measurements


Author(s): Quntao Zhuang, Zheshen Zhang, and Jeffrey H. Shapiro

Lidar is a well-known optical technology for measuring a target's range and radial velocity. We describe two lidar systems that use entanglement between transmitted signals and retained idlers to obtain significant quantum enhancements in simultaneous measurements of these parameters. The first enta...

[Phys. Rev. A 96, 040304(R)] Published Mon Oct 16, 2017

Transfer and preservation of entanglement in a hybrid optomechanical system


Author(s): Qiankun Zhang, Xiangyang Zhang, and Lianzhen Liu

We propose a scheme for entangling a movable mirror and two atomic ensembles in a coupled hybrid optomechanical system. Using the logarithmic negativity for the entanglement measure, we analyze the effect of the coupling strength between the two cavities on the entanglement of the movable mirror and...

[Phys. Rev. A 96, 042320] Published Mon Oct 16, 2017

Verifying bound entanglement of dephased Werner states


Author(s): P. Thomas, M. Bohmann, and W. Vogel

The verification of quantum entanglement under the influence of realistic noise and decoherence is crucial for the development of quantum technologies. Unfortunately, a full entanglement characterization is generally not possible with most entanglement criteria such as entanglement witnesses or the ...

[Phys. Rev. A 96, 042321] Published Mon Oct 16, 2017

Experimental demonstration of perturbative anticrossing mitigation using nonuniform driver Hamiltonians


Author(s): Trevor Lanting, Andrew D. King, Bram Evert, and Emile Hoskinson

Perturbative anticrossings have long been identified as a potential computational bottleneck for quantum annealing. This bottleneck can appear, for example, when a uniform transverse driver Hamiltonian is applied to each qubit. Previous theoretical research sought to alleviate such anticrossings by ...

[Phys. Rev. A 96, 042322] Published Mon Oct 16, 2017

Tight upper bound for the maximal quantum value of the Svetlichny operators


Author(s): Ming Li, Shuqian Shen, Naihuan Jing, Shao-Ming Fei, and Xianqing Li-Jost

It is a challenging task to detect genuine multipartite nonlocality (GMNL). In this paper, the problem is considered via computing the maximal quantum value of Svetlichny operators for three-qubit systems and a tight upper bound is obtained. The constraints on the quantum states for the tightness of...

[Phys. Rev. A 96, 042323] Published Mon Oct 16, 2017

Role of coherence during classical and quantum decoherence


Author(s): Jin-Xing Hou, Si-Yuan Liu, Xiao-Hui Wang, and Wen-Li Yang

The total correlation in a bipartite quantum system is measured by the quantum mutual information $\mathcal{I}$, which consists of quantum discord and classical correlation. However, recent results in quantum information show that coherence, which is a part of total correlation, is more general and ...

[Phys. Rev. A 96, 042324] Published Mon Oct 16, 2017

Thermal effects on coherence and excitation transfer


Author(s): Laleh Memarzadeh and Azam Mani

To control and utilize quantum features in small scale for practical applications such as quantum transport, it is crucial to gain a deep understanding of the quantum characteristics of states such as coherence. Here by introducing a technique that simplifies solving the dynamical equation, we study...

[Phys. Rev. A 96, 042318] Published Fri Oct 13, 2017

Estimation of gradients in quantum metrology


Author(s): Sanah Altenburg, Michał Oszmaniec, Sabine Wölk, and Otfried Gühne

We develop a general theory to estimate magnetic field gradients in quantum metrology. We consider a system of $N$ particles distributed on a line whose internal degrees of freedom interact with a magnetic field. Usually gradient estimation is based on precise measurements of the magnetic field at t...

[Phys. Rev. A 96, 042319] Published Fri Oct 13, 2017

Resonator reset in circuit QED by optimal control for large open quantum systems


Author(s): Samuel Boutin, Christian Kraglund Andersen, Jayameenakshi Venkatraman, Andrew J. Ferris, and Alexandre Blais

We study an implementation of the open GRAPE (gradient ascent pulse engineering) algorithm well suited for large open quantum systems. While typical implementations of optimal control algorithms for open quantum systems rely on explicit matrix exponential calculations, our implementation avoids thes...

[Phys. Rev. A 96, 042315] Published Thu Oct 12, 2017

Fault-tolerance thresholds for the surface code with fabrication errors


Author(s): James M. Auger, Hussain Anwar, Mercedes Gimeno-Segovia, Thomas M. Stace, and Dan E. Browne

The construction of topological error correction codes requires the ability to fabricate a lattice of physical qubits embedded on a manifold with a nontrivial topology such that the quantum information is encoded in the global degrees of freedom (i.e., the topology) of the manifold. However, the man...

[Phys. Rev. A 96, 042316] Published Thu Oct 12, 2017

Quantum gate description for induced coherence without induced emission and its applications


Author(s): Sahar Alipour, Mario Krenn, and Anton Zeilinger

We introduce unitary quantum gates for photon pair creation in spontaneous parametric down-conversion nonlinear crystals (NLs) and for photon path alignment. These are the two key ingredients for the method of induced coherence without induced emission and many ensuing variations thereof. The diffic...

[Phys. Rev. A 96, 042317] Published Thu Oct 12, 2017

Optimally cloned binary coherent states


Author(s): C. R. Müller, G. Leuchs, Ch. Marquardt, and U. L. Andersen

Binary coherent state alphabets can be represented in a two-dimensional Hilbert space. We capitalize this formal connection between the otherwise distinct domains of qubits and continuous variable states to map binary phase-shift keyed coherent states onto the Bloch sphere and to derive their quantu...

[Phys. Rev. A 96, 042311] Published Wed Oct 11, 2017

Imperfect state preparation in continuous-variable quantum key distribution


Author(s): Wenyuan Liu, Xuyang Wang, Ning Wang, Shanna Du, and Yongmin Li

In continuous-variable quantum key distribution, the loss and excess noise of the quantum channel are key parameters that determine the secure key rate and the maximal distribution distance. We investigate the imperfect quantum state preparation in Gaussian modulation coherent-state protocol both th...

[Phys. Rev. A 96, 042312] Published Wed Oct 11, 2017

Necessary condition for local distinguishability of maximally entangled states: Beyond orthogonality preservation


Author(s): Tanmay Singal, Ramij Rahaman, Sibasish Ghosh, and Guruprasad Kar

The (im)possibility of local distinguishability of orthogonal multipartite quantum states still remains an intriguing question. Beyond ${\mathbb{C}}^{3}⊗{\mathbb{C}}^{3}$, the problem remains unsolved even for maximally entangled states (MESs). So far, the only known condition for the local distingu...

[Phys. Rev. A 96, 042314] Published Wed Oct 11, 2017

Quantum annealing with a nonvanishing final value of the transverse field


Author(s): Kohji Nishimura and Hidetoshi Nishimori

We study the problem to infer the original ground state of a spin-glass Hamiltonian out of the information from the Hamiltonian with interactions deviated from the original ones. Our motivation comes from quantum annealing on a real device in which the values of interactions are degraded by noise. W...

[Phys. Rev. A 96, 042310] Published Tue Oct 10, 2017

High-fidelity Rydberg quantum gate via a two-atom dark state


Author(s): David Petrosyan, Felix Motzoi, Mark Saffman, and Klaus Mølmer

A modified Rydberg blockade gate that employs adiabatic following of a two-atom dark state is proposed. The scheme is resilient to the uncertainty in the interaction strength and can be employed to achieve fault-tolerant quantum computation with neutral atoms.

[Phys. Rev. A 96, 042306] Published Mon Oct 09, 2017

Noiseless attenuation using an optical parametric amplifier


Author(s): R. A. Brewster, I. C. Nodurft, T. B. Pittman, and J. D. Franson

The process of heralded noiseless amplification, and the inverse process of heralded noiseless attenuation, have potential applications in the context of quantum communications. Although several different physical implementations of heralded noiseless amplifiers have now been demonstrated, the resea...

[Phys. Rev. A 96, 042307] Published Mon Oct 09, 2017

Dissipative generation of a steady three-atom singlet state based on Rydberg pumping


Author(s): Xiang Chen, Hong Xie, Gong-Wei Lin, Xiao Shang, Ming-Yong Ye, and Xiu-Min Lin

Multiparticle singlet states are special quantum entangled states that have been shown to have many interesting applications. We develop a simple scheme to prepare a steady three-atom singlet state with a dissipative Rydberg pumping process, which combines dissipative dynamics and Rydberg interactio...

[Phys. Rev. A 96, 042308] Published Mon Oct 09, 2017

Benchmarking the state comparison amplifier


Author(s): Klaudia Kleczkowska, Ittoop Vergheese Puthoor, Lauren Bain, and Erika Andersson

The state comparison amplifier is a recently proposed probabilistic quantum amplifier, intended especially for amplifying coherent states. Its realization is simple and uses only linear optics and photodetectors, and the preparation of a “guess” state, typically a coherent state. Fidelity and succes...

[Phys. Rev. A 96, 042309] Published Mon Oct 09, 2017

Quantification of multidimensional entanglement stored in a crystal


Author(s): Alexey Tiranov, Sébastien Designolle, Emmanuel Zambrini Cruzeiro, Jonathan Lavoie, Nicolas Brunner, Mikael Afzelius, Marcus Huber, and Nicolas Gisin

The use of multidimensional entanglement opens new perspectives for quantum information processing. However, an important challenge in practice is to certify and characterize multidimensional entanglement from measurement data that are typically limited. Here, we report the certification and quantif...

[Phys. Rev. A 96, 040303(R)] Published Fri Oct 06, 2017

Second law of thermodynamics with quantum memory


Author(s): Li-Hang Ren and Heng Fan

We design a heat engine with multiheat reservoir, an ancillary system, and quantum memory. We then derive an inequality related to the second law of thermodynamics and give a limitation on the work gain from the engine by analyzing the entropy change and quantum mutual information change during the ...

[Phys. Rev. A 96, 042304] Published Fri Oct 06, 2017

Millimeter-wave interconnects for microwave-frequency quantum machines


Author(s): Marek Pechal and Amir H. Safavi-Naeini

Superconducting microwave circuits form a versatile platform for storing and manipulating quantum information. A major challenge to further scalability is to find approaches for connecting these systems over long distances and at high rates. One approach is to convert the quantum state of a microwav...

[Phys. Rev. A 96, 042305] Published Fri Oct 06, 2017

Hardness of classically sampling the one-clean-qubit model with constant total variation distance error


Author(s): Tomoyuki Morimae

The one-clean-qubit model (or the DQC1 model) is a restricted model of quantum computing where only a single input qubit is pure and all other input qubits are maximally mixed. In spite of the severe restriction, the model can solve several problems (such as calculating Jones polynomials) whose clas...

[Phys. Rev. A 96, 040302(R)] Published Thu Oct 05, 2017

Clustering in Hilbert space of a quantum optimization problem


Author(s): S. C. Morampudi, B. Hsu, S. L. Sondhi, R. Moessner, and C. R. Laumann

The solution space of many classical optimization problems breaks up into clusters which are extensively distant from one another in the Hamming metric. Here, we show that an analogous quantum clustering phenomenon takes place in the ground-state subspace of a certain quantum optimization problem. T...

[Phys. Rev. A 96, 042303] Published Thu Oct 05, 2017

Continuous-time quantum walks on spatially correlated noisy lattices


Author(s): Matteo A. C. Rossi, Claudia Benedetti, Massimo Borrelli, Sabrina Maniscalco, and Matteo G. A. Paris

We address memory effects and diffusive properties of a continuous-time quantum walk on a one-dimensional percolation lattice affected by spatially correlated random telegraph noise. In particular, by introducing spatially correlated time-dependent fluctuations in nearest-neighbor hopping amplitudes...

[Phys. Rev. A 96, 040301(R)] Published Wed Oct 04, 2017

Error rates and resource overheads of encoded three-qubit gates


Author(s): Ryuji Takagi, Theodore J. Yoder, and Isaac L. Chuang

A non-Clifford gate is required for universal quantum computation, and, typically, this is the most error-prone and resource-intensive logical operation on an error-correcting code. Small, single-qubit rotations are popular choices for this non-Clifford gate, but certain three-qubit gates, such as T...

[Phys. Rev. A 96, 042302] Published Wed Oct 04, 2017

Quenched dynamics of entangled states in correlated quantum dots


Author(s): N. S. Maslova, P. I. Arseyev, and V. N. Mantsevich

The time evolution of an initially prepared entangled state in the system of coupled quantum dots has been analyzed by means of two different theoretical approaches: equations of motion for all orders localized electron correlation functions, considering interference effects, and kinetic equations f...

[Phys. Rev. A 96, 042301] Published Mon Oct 02, 2017

Quantum microwave-optical interface with nitrogen-vacancy centers in diamond


Author(s): Bo Li, Peng-Bo Li, Yuan Zhou, Sheng-Li Ma, and Fu-Li Li

We propose an efficient scheme for a coherent quantum interface between microwave and optical photons using nitrogen-vacancy (NV) centers in diamond. In this setup, an NV center ensemble is simultaneously coupled to an optical and a microwave cavity. We show that, by using the collective spin excita...

[Phys. Rev. A 96, 032342] Published Fri Sep 29, 2017

Bayesian view of single-qubit clocks, and an energy versus accuracy tradeoff


Author(s): Manoj Gopalkrishnan, Varshith Kandula, Praveen Sriram, Abhishek Deshpande, and Bhaskaran Muralidharan

We bring a Bayesian approach to the analysis of clocks. Using exponential distributions as priors for clocks, we analyze how well one can keep time with a single qubit freely precessing under a magnetic field. We find that, at least with a single qubit, quantum mechanics does not allow exact timekee...

[Phys. Rev. A 96, 032339] Published Thu Sep 28, 2017

Classical capacity per unit cost for quantum channels


Author(s): Marcin Jarzyna

In most communication scenarios, sending a symbol encoded in a quantum state requires spending resources such as energy, which can be quantified by a cost of communication. A standard approach in this context is to quantify the performance of communication protocol by classical capacity, quantifying...

[Phys. Rev. A 96, 032340] Published Thu Sep 28, 2017

Fault tolerance with bare ancillary qubits for a [[7,1,3]] code


Author(s): Muyuan Li, Mauricio Gutiérrez, Stanley E. David, Alonzo Hernandez, and Kenneth R. Brown

We present a $[[7,1,3]]$ quantum error-correcting code that is able to achieve fault-tolerant syndrome measurement using one ancillary qubit per stabilizer for an error model of independent single-qubit Pauli errors. All single-qubit Pauli errors on the ancillary qubits propagate to form exclusively...

[Phys. Rev. A 96, 032341] Published Thu Sep 28, 2017

Nonuniform code concatenation for universal fault-tolerant quantum computing


Author(s): Eesa Nikahd, Mehdi Sedighi, and Morteza Saheb Zamani

Using transversal gates is a straightforward and efficient technique for fault-tolerant quantum computing. Since transversal gates alone cannot be computationally universal, they must be combined with other approaches such as magic state distillation, code switching, or code concatenation to achieve...

[Phys. Rev. A 96, 032337] Published Wed Sep 27, 2017