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We derive an experimentally observable lower bound on concurrence of mixed quantum states in terms of an entanglement witness, relating measurements on single states with those on two copies.

Quantum Physics · Physics 2009-11-13 Florian Mintert

We introduce a general framework for detecting genuine multipartite entanglement and non full-separability in multipartite quantum systems of arbitrary dimensions based on correlation tensors. Regarding genuine multipartite entanglement our…

Quantum Physics · Physics 2011-12-08 Julio I. de Vicente , Marcus Huber

We study the concurrence of arbitrary multipartite mixed quantum states. An explicit lower bound of the concurrence is derived, which detects quantum entanglement of some states better than some separability criteria, and gives sufficient…

Quantum Physics · Physics 2009-11-13 Ming Li , Shao-Ming Fei , Zhi-XiWang

The problem of the experimental determination of the amount of entanglement of a bipartite pure state is addressed. We show that measuring a single observable does not suffice to determine the entanglement of a given unknown pure state of…

Quantum Physics · Physics 2009-10-31 J. M. G. Sancho , S. F. Huelga

We investigate upper and lower bounds on the entropy of entanglement of a superposition of bipartite states as a function of the individual states in the superposition. In particular, we extend the results in [G. Gour, arxiv.org:0704.1521…

Quantum Physics · Physics 2009-11-13 Gilad Gour , Aidan Roy

We introduce a potential of multipartite entanglement for a system of n qubits, as the average over all balanced bipartitions of a bipartite entanglement measure, the purity. We study in detail its expression and look for its minimizers,…

Mathematical Physics · Physics 2010-01-30 Paolo Facchi

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 generalize the Schmidt-correlated states to multipartite systems. The related equivalence under SLOCC, the separability, entanglement witness, entanglement measures of negativity, concurrence and relative entropy are investigated in…

Quantum Physics · Physics 2009-11-13 Ming-Jing Zhao , Shao-Ming Fei , Zhi-Xi Wang

Among the many facets of quantum correlations, bound entanglement has remained one the most enigmatic phenomena, despite the fact that it was discovered in the early days of quantum information. Even its detection has proven to be…

Quantum Physics · Physics 2016-09-07 Gael Sentís , Christopher Eltschka , Jens Siewert

Two-qubit states occupy a large and relatively unexplored Hilbert space. Such states can be succinctly characterized by their degree of entanglement and purity. In this letter we investigate entangled mixed states and present a class of…

Quantum Physics · Physics 2009-11-07 W. J. Munro , D. F. V. James , A. G. White , P. G. Kwiat

We present an inequality for detecting entanglement and distillability of arbitrary dimensional bipartite systems. This inequality provides a sufficient condition of entanglement for bipartite mixed states, and a necessary and sufficient…

Quantum Physics · Physics 2013-07-04 Ming-Jing Zhao , Ting-Gui Zhang , Xianqing Li-Jost , Shao-Ming Fei

Multipartite entanglement is a key resource for quantum computation. It is expected theoretically that entanglement transition may happen for multipartite random quantum states, however, which is still absent experimentally. Here, we report…

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

We explore the effect of two-dimensional position-space non-commutativity on the bipartite entanglement of continuous variable systems. We first extend the standard symplectic framework for studying entanglement of Gaussian states of…

Quantum Physics · Physics 2013-05-29 S. Adhikari , B. Chakraborty , A. S. Majumdar , S. Vaidya

We present a general theory for the construction of witnesses that detect genuine multipartite entanglement in graph states. First, we present explicit witnesses for all graph states of up to six qubits which are better than all criteria so…

Quantum Physics · Physics 2011-10-26 Bastian Jungnitsch , Tobias Moroder , Otfried Gühne

This note quantifies the continuity properties of entanglement: how much does entanglement vary if we change the entangled quantum state just a little? This question is studied for the pure state entanglement of a bipartite system and for…

Quantum Physics · Physics 2009-10-31 M. A. Nielsen

We present a method to find the decompositions of tripartite entangled pure states which are smaller than two successive Schmidt decompositions. The method becomes very simple when one of the subsystems is a qubit. In this particular case,…

Quantum Physics · Physics 2009-11-11 Marcio F. Cornelio , A. F. R. de Toledo Piza

We construct entanglement witnesses with regard to the geometric structure of the Hilbert--Schmidt space and investigate the geometry of entanglement. In particular, for a two--parameter family of two--qutrit states that are part of the…

Quantum Physics · Physics 2009-07-07 Reinhold A. Bertlmann , Philipp Krammer

We develop a novel necessary condition of quantum correlation. It is utilized to construct $d$-level bipartite Bell-type inequality which is strongly resistant to noise and requires only analyses of $O(d)$ measurement outcomes compared to…

Quantum Physics · Physics 2007-09-14 Che-Ming Li , Li-Yi Hsu , Yueh-Nan Chen , Der-San Chuu , Tobias Brandes

Entanglement between three or more parties exhibits a realm of properties unknown to two-party states. Bipartite states are easily classified using the Schmidt decomposition. The Schmidt coefficients of a bipartite pure state encompass all…

Quantum Physics · Physics 2008-12-18 Julia Kempe