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Recently, the fast development of quantum technologies led to the need for tools allowing the characterization of quantum resources. In particular, the ability to estimate non-classical aspects, e.g. entanglement and quantum discord, in…

A new quantum correlation in terms of the average distance between the reduced state and the $i$-th output reduced states under local von Neumann measurements is proposed. It is shown that only the product states do not contain this quantum…

Quantum Physics · Physics 2015-05-12 Yu Guo , Xiulan Li , Bo Li , Heng Fan

We propose that the entanglement of mixed states is characterised properly in terms of a probability density function $\mathcal{P}(\mathcal{E})$. There is a need for such a measure since the prevalent measures (such as \textit{concurrence}…

Quantum Physics · Physics 2007-05-23 Shanthanu Bhardwaj , V. Ravishankar

We study the distinguishability of bipartite quantum states by Positive Operator-Valued Measures with positive partial transpose (PPT POVMs). The contributions of this paper include: (1). We give a negative answer to an open problem of [M.…

Quantum Physics · Physics 2014-04-02 Nengkun Yu , Runyao Duan , Mingsheng Ying

Entanglement witnesses provide tools to detect entanglement in experimental situations without the need of having full tomographic knowledge about the state. If one estimates in an experiment an expectation value smaller than zero, one can…

Quantum Physics · Physics 2013-08-28 Jens Eisert , Fernando G. S. L. Brandao , Koenraad M. R. Audenaert

An intrinsic relation between maximally entangled states and entanglement measures is revealed, which plays a role in establishing connections for different entanglement quantifiers. We exploit the basic idea and propose a framework to…

Quantum Physics · Physics 2008-11-21 Jianming Cai , Wei Song

Motivated by the increasing ability of experimentalists to perform detector tomography, we consider how to incorporate the imperfections and restrictions of available measurements directly into the quantification of entanglement. Exploiting…

Quantum Physics · Physics 2012-10-31 Sebastian Meznaric

By calculating entanglement measures and quantum violation of Bell-type inequality, we reveal the relationship between entanglement measure and the amount of quantum violation for a family of four-qubit entangled states. It has been…

Quantum Physics · Physics 2017-06-07 Dong Ding , Yingqiu He , Fengli Yan , Ting Gao

The degree to which a pure quantum state is entangled can be characterized by the distance or angle to the nearest unentangled state. This geometric measure of entanglement, already present in a number of settings [A. Shimony, Ann. NY.…

Quantum Physics · Physics 2007-05-23 Tzu-Chieh Wei , Paul M. Goldbart

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

The problem of ordering of two-qubit states imposed by relative entropy of entanglement (E) in comparison to concurrence (C) and negativity (N) is studied. Analytical examples of states consistently and inconsistently ordered by the…

Quantum Physics · Physics 2009-08-03 Adam Miranowicz , Andrzej Grudka

For parameter estimation from an $N$-component composite quantum system, it is known that a separable preparation leads to a mean-squared estimation error scaling as $1/N$ while an entangled preparation can in some conditions afford a…

Quantum Physics · Physics 2019-04-04 Francois Chapeau-Blondeau

In this work we study the entanglement of pure fourpartite of qubit states. The analysis is realized through the comparison between two different entanglement measures: the Groverian entanglement measure and the residual entanglement…

Quantum Physics · Physics 2009-02-04 David Sena Oliveira , Rubens Viana Ramos

Our study employs a connected correlation matrix to quantify Quantum Entanglement. The matrix encompasses all necessary measures for assessing the degree of entanglement between particles. We begin with a three-qubit state and involve…

Quantum Physics · Physics 2023-12-06 Xingyu Guo , Chen-Te Ma

We propose that the entanglement of mixed states is characterised properly in terms of a probability density function $\mathcal{P}_{\rho}(\mathcal{E})$. There is a need for such a measure since the prevalent measures (such as…

Quantum Physics · Physics 2009-11-13 Shanthanu Bhardwaj , V. Ravishankar

We analyse decoherence properties of entangled coherent states (ECSs) due to channel losses, and compare to the performance of bi-photon Bell states. By employing the concept of "entanglement of formation" (EOF), the degradation of fidelity…

Quantum Physics · Physics 2013-03-21 Yao Yao , Hong-Wei Li , Zhen-Qiang Yin , Guang-Can Guo , Zheng-Fu Han

Entanglement is recognized as a key resource for quantum computation and quantum cryptography. For quantum metrology, the use of entangled states has been discussed and demonstrated as a means of improving the signal-to-noise ratio. In…

Quantum Physics · Physics 2007-05-23 C. F. Roos , M. Chwalla , K. Kim , M. Riebe , R. Blatt

We propose a new measure of non-classicality of quantum gates which is particularly suitable for probabilistic devices. This measure enables to compare, e.g., deterministic devices which prepare entangled states with low amount of…

Quantum Physics · Physics 2013-07-01 Karel Lemr , Antonín Černoch , Jan Soubusta , Miloslav Dušek

In this paper, we investigate how to quantify the quantum states of $n$-particles from the point of $(k+1)$-partite entanglement $(1\leq k\leq n-1)$, which plays an instrumental role in quantum nonlocality and quantum metrology. We put…

Quantum Physics · Physics 2025-09-09 Hui Li , Ting Gao , Fengli Yan

The minimum error probability for distinguishing between two quantum states is bounded by the Helstrom limit, derived under the assumption that measurement strategies are restricted to positive operator-valued measurements. We explore…

Quantum Physics · Physics 2026-01-28 Swati Choudhary , Aparajita Bhattacharyya , Ujjwal Sen