Activation of entanglement in generalized entanglement swapping

PRA: Quantum information - Thu, 2024-05-23 12:00

Author(s): Pratapaditya Bej and Abhishek Banerjee

We study entanglement activation in a generalized entanglement swapping process involving two Bell pairs and generalized measurements. The conventional understanding posits entangled measurements as both necessary and sufficient for establishing entanglement between distant parties. In this study, w…

[Phys. Rev. A 109, 052437] Published Thu May 23, 2024

Categories: Journals, Physics

When superconductivity crosses over: From BCS to BEC

Reviews of Modern Physics - Thu, 2024-05-23 12:00

Author(s): Qijin Chen, Zhiqiang Wang, Rufus Boyack, Shuolong Yang, and K. Levin

The theory of unconventional superconductors continues to provide profound puzzles. The crossover between the weakly coupled Bardeen-Cooper-Schrieffer (BCS) state and the strong-pairing Bose-Einstein condensate (BEC) provides a useful perspective on how to address these questions. This paper describes a self-consistent framework for thinking about the crossover regime in between these two limits. The review discusses to what extent this BCS-BEC theory applies to a range of classes of superconducting materials including the cuprates, iron pnictides, twisted bilayer graphene, and interfacial superconductivity among others.

[Rev. Mod. Phys. 96, 025002] Published Thu May 23, 2024

Categories: Journals, Physics

Experimental Realization of Self-Contained Quantum Refrigeration

Author(s): Keyi Huang, Cheng Xi, Xinyue Long, Hongfeng Liu, Yu-ang Fan, Xiangyu Wang, Yuxuan Zheng, Yufang Feng, Xinfang Nie, and Dawei Lu

A fundamental challenge in quantum thermodynamics is the exploration of inherent dimensional constraints in thermodynamic machines. In the context of two-level systems, the most compact refrigerator necessitates the involvement of three entities, operating under self-contained conditions that preclu…

[Phys. Rev. Lett. 132, 210403] Published Thu May 23, 2024

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Discrete-phase-randomized twin-field quantum key distribution with advantage distillation

PRA: Quantum information - Wed, 2024-05-22 12:00

Author(s): Chun-Mei Zhang, Zhe Wang, Yu-Da Wu, Jian-Rong Zhu, Rong Wang, and Hong-Wei Li

The twin-field quantum key distribution (TF-QKD) protocol and its variants provide promising solutions to long-distance information-theoretic-secure communication, which can surpass the fundamental rate-loss bound without quantum repeaters. Different from other variants, the discrete-phase-randomize…

[Phys. Rev. A 109, 052432] Published Wed May 22, 2024

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Dynamical signatures of non-Markovianity in a dissipative-driven qubit

PRA: Quantum information - Wed, 2024-05-22 12:00

Author(s): Graziano Amati

We investigate signatures of non-Markovianity in the dynamics of a periodically driven qubit coupled to a dissipative bosonic environment. We propagate the dynamics of the reduced density matrix of the qubit by integrating the numerically exact hierarchical equations of motion. Non-Markovian feature…

[Phys. Rev. A 109, 052433] Published Wed May 22, 2024

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Limited quantum advantage for stellar interferometry via continuous-variable teleportation

PRA: Quantum information - Wed, 2024-05-22 12:00

Author(s): Zixin Huang, Ben Q. Baragiola, Nicolas C. Menicucci, and Mark M. Wilde

We consider stellar interferometry in the continuous-variable (CV) quantum information formalism and use the quantum Fisher information (QFI) to characterize the performance of three key strategies: direct interferometry (DI), local heterodyne measurement, and a CV teleportation-based strategy. In t…

[Phys. Rev. A 109, 052434] Published Wed May 22, 2024

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Observation of Diverse Asymmetric Structures in High-Dimensional Einstein-Podolsky-Rosen Steering

Author(s): Rui Qu, Chao Zhang, Ze-Hong Chang, Xiao-Lin Zhang, Yu Guo, Xiao-Min Hu, Chuan-Feng Li, Guang-Can Guo, Pei Zhang, and Bi-Heng Liu

Einstein-Podolsky-Rosen (EPR) steering, a distinctive quantum correlation, reveals a unique and inherent asymmetry. This research delves into the multifaceted asymmetry of EPR steering within high-dimensional quantum systems, exploring both theoretical frameworks and experimental validations. We int…

[Phys. Rev. Lett. 132, 210202] Published Wed May 22, 2024

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Nonreciprocal Quantum Batteries

Author(s): B. Ahmadi, P. Mazurek, P. Horodecki, and S. Barzanjeh

Coupling the charger and battery to a common reservoir induces a direct flow of energy into the battery.

[Phys. Rev. Lett. 132, 210402] Published Wed May 22, 2024

Categories: Journals, Physics

Ground State Nature and Nonlinear Squeezing of Gottesman-Kitaev-Preskill States

Author(s): Petr Marek

The main bottleneck for universal quantum computation with traveling light is the preparation of Gottesman-Kitaev-Preskill states of sufficient quality. This is an extremely challenging task, experimental as well as theoretical, also because there is currently no single easily computable measure of …

[Phys. Rev. Lett. 132, 210601] Published Wed May 22, 2024

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Device-Independent Quantum Key Distribution with Arbitrarily Small Nonlocality

Author(s): Lewis Wooltorton, Peter Brown, and Roger Colbeck

Device-independent quantum key distribution allows two users to set up shared cryptographic key without the need to trust the quantum devices used. Doing so requires nonlocal correlations between the users. However, in Farkas et al. [Phys. Rev. Lett. 127, 050503 (2021)] it was shown that for known p…

[Phys. Rev. Lett. 132, 210802] Published Wed May 22, 2024

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Unbounded Device-Independent Quantum Key Rates from Arbitrarily Small Nonlocality

Author(s): Máté Farkas

Device-independent quantum key distribution allows for proving the security of a shared cryptographic key between two distant parties with potentially untrusted devices. The security proof is based on the measurement outcome statistics (correlation) of a Bell experiment, and security is guaranteed b…

[Phys. Rev. Lett. 132, 210803] Published Wed May 22, 2024

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Combinatorial optimization with quantum imaginary time evolution

PRA: Quantum information - Tue, 2024-05-21 12:00

Author(s): Nora M. Bauer, Rizwanul Alam, George Siopsis, and James Ostrowski

We use quantum imaginary-time evolution (QITE) to solve polynomial unconstrained binary optimization (PUBO) problems. We show that a linear ansatz yields good results for a wide range of PUBO problems, often outperforming standard classical methods, such as the Goemans-Williamson (GW) algorithm. We …

[Phys. Rev. A 109, 052430] Published Tue May 21, 2024

Categories: Journals, Physics

Fermionic Hamiltonians without trivial low-energy states

PRA: Quantum information - Tue, 2024-05-21 12:00

Author(s): Yaroslav Herasymenko, Anurag Anshu, Barbara M. Terhal, and Jonas Helsen

One of the main problems in computational physics is predicting the low-energy behavior of many-body quantum systems. The computational complexity of this problem, however, is relatively poorly understood. A recent major progress in this direction has been the no low-energy trivial states (NLTS) the…

[Phys. Rev. A 109, 052431] Published Tue May 21, 2024

Categories: Journals, Physics

Editorial: Coauthor! Coauthor!

Reviews of Modern Physics - Tue, 2024-05-21 12:00

Author(s): Randall D. Kamien and Daniel Ucko

[Rev. Mod. Phys. 96, 020001] Published Tue May 21, 2024

Categories: Journals, Physics

Entanglement Growth via Splitting of a Few Thermal Quanta

Author(s): Pradip Laha, Darren W. Moore, and Radim Filip

Quanta splitting is an essential generator of Gaussian entanglement, exemplified by Einstein-Podolsky-Rosen states and apparently the most commonly occurring form of entanglement. In general, it results from the strong pumping of a nonlinear process with a highly coherent and low-noise external driv…

[Phys. Rev. Lett. 132, 210201] Published Mon May 20, 2024

Categories: Journals, Physics

Robust Spectral $π$ Pairing in the Random-Field Floquet Quantum Ising Model

Author(s): Harald Schmid, Alexander-Georg Penner, Kang Yang, Leonid Glazman, and Felix von Oppen

Motivated by an experiment on a superconducting quantum processor [X. Mi et al., Science 378, 785 (2022).], we study level pairings in the many-body spectrum of the random-field Floquet quantum Ising model. The pairings derive from Majorana zero and π modes when writing the spin model in Jordan-Wig…

[Phys. Rev. Lett. 132, 210401] Published Mon May 20, 2024

Categories: Journals, Physics

Quantum-Enhanced Metrology with Network States

Author(s): Yuxiang Yang, Benjamin Yadin, and Zhen-Peng Xu

Armed with quantum correlations, quantum sensors in a network have shown the potential to outclass their classical counterparts in distributed sensing tasks such as clock synchronization and reference frame alignment. On the other hand, this analysis was done for simple and idealized networks, where…

[Phys. Rev. Lett. 132, 210801] Published Mon May 20, 2024

Categories: Journals, Physics

Multiple-quadrature-amplitude-modulation continuous-variable quantum key distribution realization with a downstream-access network

PRA: Quantum information - Fri, 2024-05-17 12:00

Author(s): Junyu Zhang, Xiangyu Wang, Fan Xia, Song Yu, and Ziyang Chen

Quantum networks based on quantum key distribution ensure the security which is guaranteed by the fundamental laws of quantum physics between multiple parties. The discrete-modulation (DM) continuous-variable quantum key distribution (CV-QKD) protocols have the characteristics of simple implementati…

[Phys. Rev. A 109, 052429] Published Fri May 17, 2024

Categories: Journals, Physics

Generation of squeezed Fock states by measurement

PRA: Quantum information - Thu, 2024-05-16 12:00

Author(s): S. B. Korolev, E. N. Bashmakova, A. K. Tagantsev, and T. Yu. Golubeva

The generation of squeezed Fock states by the one or more photon subtraction from a two-mode entangled Gaussian (TMEG) state is theoretically addressed. We showed that an arbitrary order Fock state can be generated this way and we obtained a condition that should be imposed on the parameters of the …

[Phys. Rev. A 109, 052428] Published Thu May 16, 2024

Categories: Journals, Physics

Coherence Manipulation in Asymmetry and Thermodynamics

Author(s): Tulja Varun Kondra, Ray Ganardi, and Alexander Streltsov

In the classical regime, thermodynamic state transformations are governed by the free energy. This is also called as the second law of thermodynamics. Previous works showed that, access to a catalytic system allows us to restore the second law in the quantum regime when we ignore coherence. However,…

[Phys. Rev. Lett. 132, 200201] Published Thu May 16, 2024

Categories: Journals, Physics
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