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Certifying entanglement of a multipartite state is generally considered as a demanding task. Since an $N$ qubit state is parametrized by $4^{N}-1$ real numbers, one might naively expect that the measurement effort of generic entanglement…

Quantum Physics · Physics 2016-11-23 Lukas Knips , Christian Schwemmer , Nico Klein , Marcin Wieśniak , Harald Weinfurter

Separability is an important problem in theory of quantum entanglement. By using the Bloch representation of quantum states in terms of the Heisenberg-Weyl observable basis, we present a new separability criterion for bipartite quantum…

Quantum Physics · Physics 2020-02-04 Jingmei Chang , Meiyu Cui , Tinggui Zhang , Shao-Ming Fei

We show that spin squeezing criteria commonly used for entanglement detection can be erroneous, if the probe is not symmetric. We then derive a lower bound on squeezing for separable states in spin systems probed asymmetrically. Using this…

Quantum Physics · Physics 2017-04-19 Luca Dellantonio , Sumanta Das , Jürgen Appel , Anders Søndberg Sørensen

In this paper we present a necessary and sufficient condition of distinguishability of bipartite quantum states. It is shown that the operators to reliably distinguish states need only rounds of projective measurements and classical…

Quantum Physics · Physics 2016-09-08 Ping-Xing Chen , Cheng-Zu Li

We propose in this work a practical approach to address the longstanding and challenging problem of quantum separability, leveraging the correlation matrices of generic observables. General separability conditions are obtained by dint of…

Quantum Physics · Physics 2025-05-07 Ma-Cheng Yang , Cong-Feng Qiao

Variational quantum algorithms have emerged as a powerful tool for harnessing the potential of near-term quantum devices to address complex challenges across quantum science and technology. Yet, the robust and scalable quantification of…

Quantum Physics · Physics 2025-10-21 Vahid Azimi-Mousolou , Prashant Singh

An algorithm based on quantum phase estimation, which discriminates quantum states nondestructively within a set of arbitrary orthogonal states, is described and experimentally verified by a NMR quantum information processor. The procedure…

Quantum Physics · Physics 2016-11-30 V S Manu , Anil Kumar

We present the generalized state-dependent entropic uncertainty relations in multiple measurements setting, and the optimal lower bound is obtained by considering different measurement sequences. We then apply this uncertainty relation to…

Quantum Physics · Physics 2023-06-05 Li-Hang Ren , Yun-Hao Shi , Jin-Jun Chen , Heng Fan

Recently [Cavalcanti \textit{et al.} Nat Commun \textbf{6}, 7941 (2015)] proposed a method to certify the presence of entanglement in asymmetric networks, where some users do not have control over the measurements they are performing. Such…

Characterizing entanglement of systems composed of multiple particles is a very complex problem that is attracting increasing attention across different disciplines related to quantum physics. The task becomes even more complex when the…

Quantum Physics · Physics 2026-02-12 Shuheng Liu , Qiongyi He , Marcus Huber , Giuseppe Vitagliano

In quantum systems, entanglement corresponds to nonclassical correlation of nonlocal observables. Thus, entanglement (or, to the contrary, separability) of a given quantum state is not uniquely determined by properties of the state, but may…

Quantum Physics · Physics 2012-05-21 Iacopo Pozzana

We show that the rich structure of multipartite entanglement can be tested following a device-independent approach. Specifically we present Bell inequalities for distinguishing between different types of multipartite entanglement, without…

Quantum Physics · Physics 2015-05-30 Nicolas Brunner , James Sharam , Tamas Vertesi

Quantum inseparabilities can be classified into three inequivalent forms: entanglement, Einstein-Podolsky-Rosen (EPR) steering, and Bell's nonlocality. Bell-nonlocal states form a strict subset of EPR steerable states which also form a…

Quantum Physics · Physics 2019-05-22 Debarshi Das , Souradeep Sasmal , Sovik Roy

We present a framework for deciding whether a quantum state is separable or entangled using covariance matrices of locally measurable observables. This leads to the covariance matrix criterion as a general separability criterion. We…

Quantum Physics · Physics 2008-12-03 Oleg Gittsovich , Otfried Gühne , Philipp Hyllus , Jens Eisert

The semi-device-independent framework allows one to draw conclusions about properties of an unknown quantum system under weak assumptions. Here we present a semi-device-independent scheme for the characterisation of multipartite…

Quantum Physics · Physics 2018-12-04 Armin Tavakoli , Alastair A. Abbott , Marc-Olivier Renou , Nicolas Gisin , Nicolas Brunner

In quantum information and computation, the generation of entanglement through unitary gates remains a significant and active area of research. However, there are states termed as absolutely separable, from which entanglement cannot be…

Quantum Physics · Physics 2026-02-13 Bivas Mallick , Saheli Mukherjee , Nirman Ganguly , A. S. Majumdar

Quantum indistinguishability of non-orthogonal quantum states is a valuable resource in quantum information applications such as cryptography and randomness generation. In this article, we present a sequential state-discrimination scheme…

Quantum Physics · Physics 2026-04-28 Lemieux Wang , Hanwool Lee , Joonwoo Bae , Kieran Flatt

We review methods that allow one to detect and characterise quantum correlations in many-body systems, with a special focus on approaches which are scalable. Namely, those applicable to systems with many degrees of freedom, without…

Quantum Physics · Physics 2023-09-28 Irénée Frérot , Matteo Fadel , Maciej Lewenstein

The distribution and verification of quantum nonlocality across a network of users is essential for future quantum information science and technology applications. However, beyond simple point-to-point protocols, existing methods struggle…

We investigate the dynamics for a two level atomic system entangled to coherent states using the recently developed mode invisibility technique. Using a quantum 2-level probe, we demonstrate a way to non-destructively measure a number of…

Quantum Physics · Physics 2017-10-04 Paulina Corona-Ugalde , Marvellous Onuma-Kalu , Robert B. Mann