Sandu Popescu

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S. L. Braunstein,1 C. M. Caves,2 R. Jozsa,3 N. Linden,4 S. Popescu,4,5 and R. Schack2,6 1SEECS, University of Wales, Bangor LL57 1UT, United Kingdom 2Center for Advanced Studies, Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131-1156 3School of Mathematics and Statistics, University of Plymouth, Devon PL4 8AA,(More)
We develop a novel approach to Bell inequalities based on a constraint that the correlations exhibited by local variable theories must satisfy. This is used to construct a family of Bell inequalities for bipartite quantum systems of arbitrarily high dimensionality which are strongly resistant to noise. In particular, our work gives an analytic description(More)
We build, using group-theoretic methods, a general framework for approaching multi-particle entanglement. As far as entanglement is concerned, two states of n spin-1/2 particles are equivalent if they are on the same orbit of the group of local rotations (U(2)). We give a method for finding the number of parameters needed to describe inequivalent n spin-1/2(More)
The circumstances under which a system reaches thermal equilibrium, and how to derive this from basic dynamical laws, has been a major question from the very beginning of thermodynamics and statistical mechanics. Despite considerable progress, it remains an open problem. Motivated by this issue, we address the more general question of equilibration. We(More)
Charles H. Bennett, Sandu Popescu, Daniel Rohrlich, John A. Smolin, and Ashish V. Thapliyal IBM Research Division, Yorktown Heights, NY 10598, USA — bennetc, smolin@watson.ibm.com Isaac Newton Institute, Cambridge University, Cambridge, UK and BRIMS, Hewlett-Packard Labs., Stoke Gifford, Bristol BS12 6QZ, UK — sp230@newton.cam.ac.uk School of Physics and(More)
As is well known, quantum mechanical behavior cannot, in general, be simulated by a local hidden variables model. Most -if not allthe proofs of this incompatibility refer to the correlations which arise when each of two (or more) systems separated in space is subjected * present address: Tel Aviv University, School of Physics and Astronomy, Ramat Aviv, Tel(More)
We report on a quantum optical experimental implementation of teleportation of unknown pure quantum states. This realizes all the nonlocal aspects of the original scheme proposed by Bennett et al. and is equivalent to it up to a local operation. We exhibit results for the teleportation of a linearly polarised state and of an elliptically polarised state. We(More)
It is known that all causal correlations between two parties which output each 1 bit, a and b, when receiving each 1 bit, x and y, can be expressed as convex combinations of local correlations (i.e., correlations that can be simulated with local random variables) and nonlocal correlations of the form a+b=xy mod 2. We show that a single instance of the(More)