Konstanz 1998 – scientific programme

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Q: Quantenoptik

Q 22: Symposium Quantenkommunikation II

Q 22.2: Talk

Wednesday, March 18, 1998, 14:30–14:45, R 711

Entanglement measures, quantum state purification and channel capacities — •M. B. Plenio, V. Vedral, and P. L. Knight — Optics Section, The Blackett Laboratory, Imperial College, London SW7 2BZ, UK

We improve previously proposed conditions each measure of entanglement has to satisfy. We present a class of entanglement measures that satisfy these conditions and show that the Quantum Relative Entropy and Bures Metric generate two measures of this class. We calculate the measures of entanglement for a number of mixed two spin 1/2 systems using the Quantum Relative Entropy, and provide an efficient numerical method to obtain the measures of entanglement in this case. In addition, we prove a number of properties of our entanglement measure which have important physical implications. We briefly explain the statistical basis of our measure of entanglement in the case of the Quantum Relative Entropy. We then argue that our entanglement measure determines an upper bound to the number of singlets that can be obtained by any purification procedure.