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One of the most fascinating aspects of quantum networks is their capability to distribute entanglement as a nonlocal communication resource. In a first step, this requires network-ready devices that can generate and store entangled states.…

This paper characterizes two forms of separability of pure states of systems of n qubits: (i) into a tensor product of n qubit states, and (ii), into a tensor product of 2 subsystems states of p and q qubits respectively with p+q=n. For…

Quantum Physics · Physics 2007-05-23 Philippe Jorrand , Mehdi Mhalla

We study the convex set of all bipartite quantum states with fixed marginal states. The extremal states in this set have recently been characterized by Parthasarathy [Ann. Henri Poincar\'e (to appear), quant-ph/0307182, [1]]. Here we…

Quantum Physics · Physics 2009-11-10 Oliver Rudolph

We present a complete classification of the geometry of the mutually complementary sets of entangled and separable states in three-dimensional Hilbert subspaces of bipartite and multipartite quantum systems. Our analysis begins by finding…

Quantum Physics · Physics 2024-06-24 Rotem Liss , Tal Mor , Andreas Winter

For finite-dimensional bipartite quantum systems, we find the exact size of the largest balls, in spectral $l_p$ norms for $1 \le p \le \infty$, of separable (unentangled) matrices around the identity matrix. This implies a simple and…

Quantum Physics · Physics 2009-11-07 Leonid Gurvits , Howard Barnum

We study the robustness of the GHZ (or ``cat'') class of multi-partite states under decoherence. The noise model is described by a general completely positive map for qubits independently coupled to the environment. In particular, the…

Quantum Physics · Physics 2007-05-23 Somshubhro Bandyopadhyay , Daniel A. Lidar

We study a separability problem suggested by mathematical description of bipartite quantum systems. We consider Hermitian 2-forms on the tensor product $H=K\otimes L$, where $K,L$ are finite dimensional complex spaces. Inspired by quantum…

Mathematical Physics · Physics 2010-01-11 Bronisław Jakubczyk , Gabriel Pietrzkowski

We give a direct tensor decomposition for any density matrix into Hermitian operators. Based upon the decomposition we study when the mixed states are separable and generalize the separability indicators to multi-partite states and show…

Quantum Physics · Physics 2015-05-13 Xiaofen Huang , Naihuan Jing

The bipartite entanglement of a pure quantum state is known to be characterized by its Schmidt decomposition. In particular the state is maximally entangled when all the Schmidt coefficients are equal. We point out a convenient method which…

Quantum Physics · Physics 2008-01-09 M. Bhattacharya

Determining whether a quantum state is separable or entangled is a problem of fundamental importance in quantum information science. This is a brief review in which we consider the problem for states in infinite dimensional Hilbert spaces.…

Computational Complexity · Computer Science 2007-05-23 Stefano Mancini , Simone Severini

Entanglement is an useful resource because some global operations cannot be locally implemented using classical communication. We prove a number of results about what is and is not locally possible. We focus on orthogonal states, which can…

Quantum Physics · Physics 2009-11-07 Jonathan Walgate , Lucien Hardy

We investigate completely positive maps for an open system interacting with its environment. The families of the initial states for which the reduced dynamics can be described by a completely positive map are identified within the framework…

Quantum Physics · Physics 2014-07-09 Longjiang Liu , D. M. Tong

We introduce a new technique to detect separable states using semidefinite programs. This approach provides a sufficient condition for separability of a state that is based on the existence of a certain local linear map applied to a known…

Quantum Physics · Physics 2009-11-13 Federico M. Spedalieri

In multipartite systems, great progress has been made recently on the study of strong quantum nonlocality without entanglement. However, the existence of orthogonal product sets with strong quantum nonlocality in even party systems remains…

Quantum Physics · Physics 2023-04-27 Huaqi Zhou , Ting Gao , Fengli Yan

Measurements profoundly impact quantum systems, and can be used to create novel states of matter out of equilibrium. We investigate the multipartite entanglement structure that emerges in hybrid quantum circuits involving unitaries and…

Quantum Physics · Physics 2025-07-04 Sebastien J Avakian , T. Pereg-Barnea , William Witczak-Krempa

We investigate absolutely maximally entangled (AME) states, which are multipartite quantum states that are maximally entangled with respect to any possible bipartition. These strong entanglement properties make them a powerful resource for…

Quantum Physics · Physics 2013-06-12 Wolfram Helwig , Wei Cui

The characterization of genuine multiparticle entanglement is important for entanglement theory as well as experimental studies related to quantum information theory. Here, we completely characterize genuine multiparticle entanglement for…

Quantum Physics · Physics 2011-11-28 Otfried Gühne , Bastian Jungnitsch , Tobias Moroder , Yaakov S. Weinstein

We show how to decompose any density matrix of the simplest binary composite systems, whether separable or not, in terms of only product vectors. We determine for all cases the minimal number of product vectors needed for such a…

Quantum Physics · Physics 2009-10-31 Anna Sanpera , Rolf Tarrach , Guifre Vidal

We derive inequalities sufficient to detect the genuine $N$-partite steering of $N$ distinct systems. Here, we are careful to distinguish between the concepts of full $N$-partite steering inseparability (where steering is confirmed…

Quantum Physics · Physics 2023-07-27 Run Yan Teh , Manuel Gessner , Margaret D. Reid , Matteo Fadel

Quantum states are the key mathematical objects in quantum mechanics, and entanglement lies at the heart of the nascent fields of quantum information processing and computation. However, there has not been a general, necessary and…

Quantum Physics · Physics 2024-10-10 Bang-Hai Wang