QUROPE Quantum Information Processing and Communication in Europe

Author(s): Chengkai Zhu, Yin Mo, Yu-Ao Chen, and Xin Wang

The inherent irreversibility of quantum dynamics for open systems poses a significant barrier to the inversion of unknown quantum processes. To tackle this challenge, we propose the framework of virtual combs that exploits the unknown process iteratively with additional classical postprocessing to s…

[Phys. Rev. Lett. 133, 030801] Published Fri Jul 19, 2024

Author(s): Rui Li, Junling Du, Zheng Qin, Shikun Zhang, Chunxiao Du, Yang Zhou, and Zhisong Xiao

Quantum entanglement plays a pivotal role in various quantum information processing tasks. However, a universal and effective way to detect entanglement structures is still lacking, especially for high-dimensional and multipartite quantum systems. Noticing the mathematical similarities between the c…

[Phys. Rev. A 110, 012448] Published Fri Jul 19, 2024

Author(s): Gekko Budiutama, Shunsuke Daimon, Hirofumi Nishi, Ryui Kaneko, Tomi Ohtsuki, and Yu-ichiro Matsushita

Quantum convolutional neural networks (QCNNs) have gathered attention as one of the most promising algorithms for quantum machine learning. Reduction in the cost of training as well as improvement in performance are required for practical implementation of these models. In this study, we propose a c…

[Phys. Rev. A 110, 012447] Published Fri Jul 19, 2024

Author(s): Mirko Consiglio, Jacopo Settino, Andrea Giordano, Carlo Mastroianni, Francesco Plastina, Salvatore Lorenzo, Sabrina Maniscalco, John Goold, and Tony J. G. Apollaro

The preparation of an equilibrium thermal state of a quantum many-body system on noisy intermediate-scale quantum (NISQ) devices is an important task in order to extend the range of applications of quantum computation. Faithful Gibbs state preparation would pave the way to investigate protocols such…

[Phys. Rev. A 110, 012445] Published Thu Jul 18, 2024

Author(s): Göktuğ Karpat and Barış Çakmak

We examine the emergence of dynamical memory effects in quantum processes having indefinite time direction and causal order. In particular, we focus on the class of phase-covariant qubit channels, which encompasses some of the most significant paradigmatic open quantum system models. In order to ass…

[Phys. Rev. A 110, 012446] Published Thu Jul 18, 2024

Author(s): Tatsuhiko N. Ikeda, Sho Sugiura, and Anatoli Polkovnikov

An external periodic (Floquet) drive is believed to bring any initial state to the featureless infinite temperature state in generic nonintegrable isolated quantum many-body systems in the thermodynamic limit, irrespective of the driving frequency Ω. However, numerical or analytical evidence either …

[Phys. Rev. Lett. 133, 030401] Published Wed Jul 17, 2024

Author(s): Eric Kubischta and Ian Teixeira

We introduce twisted unitary t-groups, a generalization of unitary t-groups under a twisting by an irreducible representation. We then apply representation theoretic methods to the Knill-Laflamme error correction conditions to show that twisted unitary t-groups automatically correspond to quantum co…

[Phys. Rev. Lett. 133, 030602] Published Wed Jul 17, 2024

Author(s): Rajdeep Paul, Souradeep Sasmal, and A. K. Pan

Self-testing protocols refer to novel device-independent certification schemes wherein the devices are uncharacterized and the dimension of the system remains unspecified. The optimal quantum violation of Bell's inequality facilitates such self-testing. In this work we put forth a protocol for self-…

[Phys. Rev. A 110, 012444] Published Wed Jul 17, 2024

Author(s): Ivan Medina, Alexandre Drinko, Guilherme I. Correr, Pedro C. Azado, and Diogo O. Soares-Pinto

The energy extraction from quantum sources is a key task to develop new quantum devices such as quantum batteries (QB). In this context, one of the main figures of merit is the ergotropy, which measures the maximal amount of energy (as work) that can be extracted from the quantum source by means of …

[Phys. Rev. A 110, 012443] Published Wed Jul 17, 2024

Author(s): Simon Lieu, Yu-Jie Liu, and Alexey V. Gorshkov

An interesting problem in the field of quantum error correction involves finding a physical system that hosts a “passively protected quantum memory,” defined as an encoded qubit coupled to an environment that naturally wants to correct errors. To date, a quantum memory stable against finite-temperat…

[Phys. Rev. Lett. 133, 030601] Published Tue Jul 16, 2024

Author(s): Eyal Buks

Multistability is experimentally observed in a variety of quantum systems but cannot be derived from any theoretical model that is based on a monostable master equation. The author investigates the relation between disentanglement and multistability in the few-spin transverse Ising model and finds that multistability can be obtained in the presence of spontaneous disentanglement.

[Phys. Rev. A 110, 012439] Published Mon Jul 15, 2024

Author(s): Katarzyna Siudzińska

We use symmetric measurement operators to construct quantum channels that provide a further generalization of generalized Pauli channels. The resulting maps are bistochastic but, in general, no longer mixed unitary. We analyze their important properties, such as complete positivity and the ability t…

[Phys. Rev. A 110, 012440] Published Mon Jul 15, 2024

Author(s): Ming Yang, Dongkai Zhang, and Lixiang Chen

Recent advancements have expanded Hardy's nonlocality arguments into multisetting and multidimensional systems to enhance quantum correlations. In comparison with Hardy's nonlocality argument, Cabello's nonlocality argument (CNA) emerges as a superior choice for illustrating nonlocal features. An op…

[Phys. Rev. A 110, 012441] Published Mon Jul 15, 2024

Author(s): Zi-Jian Xu and Jun-Hong An

Permitting the transmission of unknown quantum states over long distances by using entanglement, quantum teleportation serves as an important building block for many quantum technologies. However, in the noisy intermediate-scale quantum era, the practical realization of quantum teleportation is inev…

[Phys. Rev. A 110, 012442] Published Mon Jul 15, 2024

Author(s): Hui-Nan Wu, Yu-Huai Li, Bo Li, Xiang You, Run-Ze Liu, Ji-Gang Ren, Juan Yin, Chao-Yang Lu, Yuan Cao, Cheng-Zhi Peng, and Jian-Wei Pan

The emergence of quantum mechanics and general relativity has transformed our understanding of the natural world significantly. However, integrating these two theories presents immense challenges, and their interplay remains untested. Recent theoretical studies suggest that the single-photon interfe…

[Phys. Rev. Lett. 133, 020201] Published Fri Jul 12, 2024

Author(s): M. Yassine Naghmouchi and Wesley da Silva Coelho

This paper presents a hybrid classical-quantum approach to solve mixed-integer linear programming (MILP) using neutral-atom quantum computations. We apply Benders decomposition (BD) to segment MILPs into a master problem (MP) and a subproblem, where the MP is addressed using a neutral-atom device, a…

[Phys. Rev. A 110, 012434] Published Fri Jul 12, 2024

Author(s): Ashutosh Goswami, Mehdi Mhalla, and Valentin Savin

A fault-tolerant way to prepare logical code states of Q1 codes, i.e., quantum polar codes encoding one qubit, was recently proposed. The fault tolerance therein is guaranteed by an error detection gadget, where, if an error is detected during the preparation, one entirely discards the preparation. …

[Phys. Rev. A 110, 012438] Published Fri Jul 12, 2024

Author(s): Steven Herbert, Julien Sorci, and Yao Tang

We give an explicit construction to perform any n-qubit computational-basis-state transposition using Θ(n) gates. This nearly coincides with the lower bound Ω[n/log(nd)] on worst-case and average-case gate complexities to perform transpositions using a d-element gate set, which we also prove.

[Phys. Rev. A 110, 012437] Published Fri Jul 12, 2024

Author(s): Ming-Ming Wang and Xiao-Ying Zhang

Bayesian networks are powerful tools for probabilistic analysis and have been widely used in machine learning and data science. Unlike the time-consuming parameter training process of neural networks, Bayes classifiers constructed on Bayesian networks can make decisions based solely on statistical d…

[Phys. Rev. A 110, 012433] Published Fri Jul 12, 2024

Author(s): Jack Ceroni, Ian MacCormack, and Guillaume Verdon

We provide a rigorous proof of the approximate convergence of sliding-window quantum belief-propagation as outlined heuristically in the work of Bilgin and Poulin [Phys. Rev. B 81, 054106 (2010)], in the absence of the quantum Markov property. In particular, we confirm the hypothesis outlined in thi…

[Phys. Rev. A 110, 012435] Published Fri Jul 12, 2024