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States of sufficiently low purity are separable and cannot be entangled by unital (purity-non-generating) operations. Since high-purity states are experimentally demanding, it is natural to ask how much purity a state must possess to enable…

The outcomes of measurements on entangled quantum systems can be nonlocally correlated. However, while it is easy to write down toy theories allowing arbitrary nonlocal correlations, those allowed in quantum mechanics are limited. Quantum…

Quantum Physics · Physics 2015-03-17 Peter Janotta , Christian Gogolin , Jonathan Barrett , Nicolas Brunner

The problem of detecting non-classical correlations of states of many qudits is incomparably more involved than in a case of qubits. The reason is that for qubits we have a convenient description of the system by the means of the…

Quantum Physics · Physics 2016-10-27 Krzysztof Rosołek , Marcin Wieśniak , Lukas Knips

Quantum systems prepared in pure states evolve into mixtures under environmental action. Physically realizable ensembles are the pure state decompositions of those mixtures that can be generated in time through continuous measurements of…

Quantum Physics · Physics 2011-02-16 Eduardo Mascarenhas , Daniel Cavalcanti , Vlatko Vedral , Marcelo Franca Santos

Entangled systems in experiments may be lost or offline in distributed quantum information processing. This inspires a general problem to characterize quantum operations which result in breaking of entanglement or not. Our goal in this work…

Quantum Physics · Physics 2022-04-21 Ming-Xing Luo , Shao-Ming Fei

Various topics concerning the entanglement of composite quantum systems are considered with particular emphasis concerning the strict relations of such a problem with the one of attributing objective properties to the constituents. Most of…

Quantum Physics · Physics 2007-05-23 Giancarlo Ghirardi , Luca Marinatto , Tullio Weber

We characterize entanglement subject to its definition over real and complex, composite quantum systems. In particular, a method is established to assess quantum correlations with respect to a selected number system, illuminating the deeply…

We introduce a new entanglement measure based on optimal entanglement witness. First of all, we show that the entanglement measure satisfies some necessary properties, including zero entanglements for all separable states, convexity,…

Quantum Physics · Physics 2024-02-20 Nan Yang , Jiaji Wu , Xianyun Dong , Longyu Xiao , Jing Wang , Ming Li

The main concern of this paper is how to define proper measures of multipartite entanglement for mixed quantum states. Since the structure of partial separability and multipartite entanglement is getting complicated if the number of…

Quantum Physics · Physics 2021-03-05 Szilárd Szalay

Pseudorandom states (PRS) are an important primitive in quantum cryptography. In this paper, we show that subset states can be used to construct PRSs. A subset state with respect to $S$, a subset of the computational basis, is \[…

Quantum Physics · Physics 2024-03-05 Fernando Granha Jeronimo , Nir Magrafta , Pei Wu

We study the separability of permutationally symmetric quantum states. We show that for bipartite symmetric systems most of the relevant entanglement criteria coincide. However, we provide a method to generate examples of bound entangled…

Quantum Physics · Physics 2009-05-12 Geza Toth , Otfried Gühne

We introduce an experimental procedure for the detection of quantum entanglement of an unknown quantum state with as few measurements as possible. The method requires neither a priori knowledge of the state nor a shared reference frame…

Quantum entanglement between particles is expected to allow one to perform tasks that would otherwise be impossible. In quantum sensing and metrology, entanglement is often claimed to enable a precision that cannot be attained with the same…

Quantum Physics · Physics 2023-09-06 Liam P. McGuinness

Squashed entanglement is a measure for the entanglement of bipartite quantum states. In this paper we present a lower bound for squashed entanglement in terms of a distance to the set of separable states. This implies that squashed…

Quantum Physics · Physics 2012-07-23 Fernando G. S. L. Brandao , Matthias Christandl , Jon Yard

Topological properties of quantum systems are one of the most intriguing emerging phenomena in condensed matter physics. A crucial property of topological systems is the symmetry-protected robustness towards local noise. Experiments have…

Quantum Physics · Physics 2022-12-05 Guliuxin Jin , Eliska Greplova

Multipartite entanglement detection is crucial for the develop of quantum information science and quantum computation, communication, simulation and metrology tasks. In contrast to experiments, where several handreds of qubits have been…

Quantum Physics · Physics 2024-11-06 Xiao-yu Chen

Bound entangled states are states that are entangled but from which no entanglement can be distilled if all parties are allowed only local operations and classical communication. However, in creating these states one needs nonzero…

Quantum Physics · Physics 2009-11-10 Tzu-Chieh Wei , Joseph B. Altepeter , Paul M. Goldbart , William J. Munro

Compact expressions for the average subentropy and coherence are obtained for random mixed states that are generated via various probability measures. Surprisingly, our results show that the average subentropy of random mixed states…

Quantum Physics · Physics 2017-02-08 Lin Zhang , Uttam Singh , Arun Kumar Pati

This paper addresses the following main question: Do we have a theoretical understanding of entanglement applicable to a full variety of physical settings? It is clear that not only the assumption of distinguishability, but also the…

Quantum Physics · Physics 2007-05-23 Gerardo Ortiz , Rolando Somma , Howard Barnum , Emanuel Knill , Lorenza Viola

Two pure orthogonal quantum states can be perfectly distinguished by sequential local action of multiple pairs of parties. However, this process typically leads to the complete dissolution of entanglement in the states being discriminated.…

Quantum Physics · Physics 2025-06-10 Debarupa Saha , Priya Ghosh , Kornikar Sen , Chirag Srivastava , Ujjwal Sen