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We exhibit an orthogonal set of product states of two three-state particles that nevertheless cannot be reliably distinguished by a pair of separated observers ignorant of which of the states has been presented to them, even if the…

We provide a canonical form of mixed states in bipartite quantum systems in terms of a convex combination of a separable state and a, so-called, edge state. We construct entanglement witnesses for all edge states. We present a canonical…

Quantum Physics · Physics 2009-11-06 M. Lewenstein , B. Kraus , P. Horodecki , J. I. Cirac

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

Using the concept of non-degenerate Bell inequality, we show that quantum entanglement, the critical resource for various quantum information processing tasks, can be quantified for any unknown quantum states in a semi-device-independent…

To address the outstanding task of detecting entanglement in large quantum systems, entanglement witnesses have emerged, addressing the separable nature of a state. Yet optimizing witnesses, or accessing them experimentally, often remains a…

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

Quantum entanglement is a unique correlation phenomenon in quantum mechanics, and the measurement of quantum entanglement plays an important role in quantum computing and quantum communication. Many mainstream entanglement criteria and…

Quantum Physics · Physics 2024-11-12 Hao-Nan Qiang , Jing-Ling Chen

It is well-known that the violation of a local uncertainty relation can be used as an indicator for the presence of entanglement. Unfortunately, the practical use of these non-linear witnesses has been limited to few special cases in the…

Quantum universal invariants of a Gaussian state's covariance matrix, which can be derived from intensity correlation moments, have been adopted to characterize the entanglement properties of Gaussian states via the positive partial…

Quantum Physics · Physics 2026-05-01 Ze-Shan He , Yukuan Zhao , Hao-Shu Tian , Kai Sun , Xiao-Ye Xu , Chuan-Feng Li , Guang-Can Guo

A convergent iterative procedure is proposed for the calculation of the relative entropy of entanglement of a given bipartite quantum state. When this state turns out to be non-separable the algorithm provides the corresponding optimal…

Quantum Physics · Physics 2009-11-07 Jaroslav Rehacek , Zdenek Hradil

There always exists an entanglement witness for every entangled quantum state. Negativity of the expectation value of an entanglement witness operator guarantees entanglement of the corresponding state, given that the measurement devices…

Quantum Physics · Physics 2021-03-24 Kornikar Sen , Chirag Srivastava , Shiladitya Mal , Aditi Sen De , Ujjwal Sen

Phase estimation is one of the most important facets of quantum metrology, with applications in sensing, microscopy, and quantum computation. When estimating a phase shift in a lossy medium, there is an upper bound on the attainable…

Quantum Physics · Physics 2024-11-26 Stewart A. Koppell , Mark A. Kasevich

The correlation matrix (CM) criterion is a recently derived powerful sufficient condition for the presence of entanglement in bipartite quantum states of arbitrary dimensions. It has been shown that it can be stronger than the positive…

Quantum Physics · Physics 2009-11-13 Julio I. de Vicente

We experimentally demonstrate the superior discrimination of separated, unentangled two-qubit correlated states using nonlocal measurements, when compared with measurements based on local operations and classical communications. When…

Quantum Physics · Physics 2008-11-26 G. J. Pryde , J. L. O'Brien , A. G. White , Stephen D. Bartlett

We consider multipartite quantum state discrimination and show that the minimum-error discrimination by separable measurements is closely related to the concept of entanglement witness. Based on the properties of entanglement witness, we…

Quantum Physics · Physics 2023-04-25 Donghoon Ha , Jeong San Kim

We show that rejection of local realism in quantum mechanics can be tested by Bell-type inequalities for two observers and low-order moments of continuous and unbounded observables. We prove that one requires three observables for each…

Quantum Physics · Physics 2020-12-11 Adam Bednorz

In this paper we study the reduction criterion for detecting entanglement of large dimensional bipartite quantum systems. We first obtain an explicit formula for the moments of a random quantum state to which the reduction criterion has…

Mathematical Physics · Physics 2014-12-02 Maria Anastasia Jivulescu , Nicolae Lupa , Ion Nechita

We derive an optimal bound for arbitrary entanglement manipulation based on the transmission of a pulse in coherent states over a lossy channel followed by local operations and unlimited classical communication (LOCC). This stands on a…

Quantum Physics · Physics 2015-05-30 Koji Azuma , Go Kato

Multipartite entanglement has been widely regarded as key resources in distributed quantum computing, for instance, multi-party cryptography, measurement based quantum computing, quantum algorithms. It also plays a fundamental role in…

Quantum Physics · Physics 2020-09-23 Nengkun Yu

Entanglement, one of the central mysteries of quantum mechanics, plays an essential role in numerous applications of quantum information theory. A natural question of both theoretical and experimental importance is whether universal…

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