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We design a series of quantum circuits that generate absolute maximally entangled (AME) states to benchmark a quantum computer. A relation between graph states and AME states can be exploited to optimize the structure of the circuits and…

Quantum Physics · Physics 2019-09-02 Alba Cervera-Lierta , José Ignacio Latorre , Dardo Goyeneche

Entanglement is the powerful and enigmatic resource central to quantum information processing, which promises capabilities in computing, simulation, secure communication, and metrology beyond what is possible for classical devices. Exactly…

Increasingly sophisticated quantum computers motivate the exploration of their abilities in certifying genuine quantum phenomena. Here, we demonstrate the power of state-of-the-art IBM quantum computers in correlation experiments inspired…

Quantum Physics · Physics 2021-07-28 Elisa Bäumer , Nicolas Gisin , Armin Tavakoli

We study entanglement-related properties of random quantum states which are unitarily invariant, in the sense that their distribution is left unchanged by conjugation with arbitrary unitary operators. In the large matrix size limit, the…

Mathematical Physics · Physics 2018-07-09 Ion Nechita

In quantum mechanics events can happen in no definite causal order: in practice this can be verified by measuring a causal witness, in the same way that an entanglement witness verifies entanglement. Indefinite causal order can be observed…

Quantum Physics · Physics 2018-11-05 K. Goswami , C. Giarmatzi , M. Kewming , F. Costa , C. Branciard , J. Romero , A. G. White

A scheme for generating an entangled state in a two spin-1/2 system by means of a spin-dependent potential scattering of another qubit is presented and analyzed in three dimensions. The entanglement is evaluated in terms of the concurrence…

Quantum Physics · Physics 2010-04-07 Yuichiro Hida , Hiromichi Nakazato , Kazuya Yuasa , Yasser Omar

Collective quantum batteries (QBs) demonstrate remarkable acceleration in charging dynamics compared to their individual counterparts, underscoring the pivotal contribution of quantum correlations to advanced energy storage paradigms. A…

Quantum Physics · Physics 2025-03-05 Hai-Long Shi , Li Gan , Kun Zhang , Xiao-Hui Wang , Wen-Li Yang

We provide a summary of both seminal and recent results on typical entanglement. By typical values of entanglement, we refer here to values of entanglement quantifiers that (given a reasonable measure on the manifold of states) appear with…

Quantum Physics · Physics 2014-09-05 Oscar C. O. Dahlsten , Cosmo Lupo , Stefano Mancini , Alessio Serafini

Covariance matrices are a useful tool to investigate correlations and entanglement in quantum systems. They are widely used in continuous variable systems, but recently also for finite dimensional systems powerful entanglement criteria in…

Quantum Physics · Physics 2010-04-22 Oleg Gittsovich , Otfried Gühne

We address the study of quantum metrology enhanced by indefinite causal order, demonstrating a quadratic advantage in the estimation of the product of two average displacements in a continuous variable system. We prove that no setup where…

Quantum Physics · Physics 2020-05-18 Xiaobin Zhao , Yuxiang Yang , Giulio Chiribella

Understanding the physical world fundamentally relies on the assumption that events are temporally ordered, with past events serving as causes for future ones. However, quantum mechanics permits events to occur in a superposition of causal…

Quantum Physics · Physics 2025-08-07 Dengke Qu , Quan Lin , Lei Xiao , Xiang Zhan , Peng Xue

First, we show how the quantum circuits for generating and measuring multi-party entanglement of qubits can be translated to continuous quantum variables. We derive sufficient inseparability criteria for $N$-party continuous-variable states…

Quantum Physics · Physics 2007-05-23 Peter van Loock , Samuel L. Braunstein

By using relative entropy of coherence, we characterize the coherence gain induced by some quantum evolutions, including the cohering power of unitary operations and the decohering power of quantum operations. We find that the cohering…

Quantum Physics · Physics 2016-07-28 Zhengjun Xi , Mingliang Hu , Yongming Li , Heng Fan

It is shown that a state that is factorizable in the Hilbert space corresponding to some choice of degrees of freedom, becomes entangled for a different choice of degrees of freedom. Therefore, entanglement is not a special case but is…

Quantum Physics · Physics 2011-05-24 A. C. de la Torre , D. Goyeneche , L. Leitao

In this proceeding, we revisit the discussion presented in Ref. [Commun Phys 7, 373 (2024)], which examines the behavior of a quantum switch involving two arbitrary quantum operations when the control is exposed to environmental effects.…

Quantum Physics · Physics 2025-03-18 Shahana Aziz , André H. A. Malavazi , Pedro R. Dieguez

The expressibility of an ansatz used in a variational quantum algorithm is defined as the uniformity with which it can explore the space of unitary matrices, i.e., its covering number. The expressibility of a particular ansatz has a…

Quantum Physics · Physics 2025-01-09 Tamojit Ghosh , Arijit Mandal , Shreya Banerjee , Neetik Mukherjee , Prasanta K. Panigrahi

(Abridged.) Quantum computers promise to solve some problems exponentially faster than traditional computers, but we still do not fully understand why this is the case. While the most studied model of quantum computation uses qubits, which…

Quantum Physics · Physics 2025-05-29 Cameron Calcluth

In quantum information and communication one looks for the non-classical features like interference and quantum correlations to harness the true power of composite systems. We show how the concept akin to interference is, in fact,…

Quantum Physics · Physics 2015-08-11 Lin Zhang , Arun Kumar Pati , Junde Wu

Quantum neural networks (QNNs), as currently formulated, are near-term quantum machine learning architectures that leverage parameterized quantum circuits with the aim of improving upon the performance of their classical counterparts. In…

Quantum Physics · Physics 2026-03-11 Marco Maronese , Francesco Ferrari , Matteo Vandelli , Daniele Dragoni

Little effort has been devoted to studying generalised notions or models of (un)predictability, yet is an important concept throughout physics and plays a central role in quantum information theory, where key results rely on the supposed…

Quantum Physics · Physics 2020-01-27 Alastair A. Abbott , Cristian S. Calude , Karl Svozil
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