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Q: Quantenoptik und Photonik
Q 23: Quanteninformation II
Q 23.7: Talk
Tuesday, March 23, 2004, 18:00–18:15, HS 101
“Squashed Entanglement” – An Additive Entanglement Measure — •Matthias Christandl1 and Andreas Winter2 — 1Centre for Quantum Computation, Department of Applied Mathematics and Theoretical Physics, Wilberforce Road, Cambridge CB3 0WA, England — 2School of Mathematics, Universtity of Bristol, University Walk, Bristol BX8 1TW, England
We present a new entanglement monotone for bipartite quantum states. Its definition is inspired by the so–called intrinsic information of classical cryptography and is given by the halved minimum quantum conditional mutual information over all tripartite state extensions. We derive certain properties of the new measure which we call “squashed entanglement”: it is a lower bound on entanglement of formation and an upper bound on distillable entanglement. Furthermore, it is convex, additive on tensor products, and superadditive in general.
Continuity in the state is the only property of our entanglement measure which we cannot provide a proof for. We present some evidence, however, that our quantity has this property, the strongest indication being a conjectured Fannes type inequality for the conditional von Neumann entropy. This inequality is proved in the classical case.