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MP: Theoretische und Mathematische Grundlagen der Physik

MP 12: Symposium: Quanteninformationsverarbeitung (gemeinsam mit Q)

MP 12.4: Hauptvortrag

Montag, 15. März 1999, 12:15–12:55, TE1

Bound entanglement and quantum communication — •Michal Horodecki — Institute of Theoretical Physics and Astrophysics, University of Gdansk, ul. Wita Stwosza 57, 80-952 Gdansk, Poland

The phenomenon of quantum teleportation shows that entanglement is a resource for quantum communication. A mixed state of a composite quantum system represents entanglement if it cannot be written as a mixture of product states. To obtain faithful teleportation, one needs to bring the state to the (almost) maximally entangled form by means of local quantum operations and classical communication. This process is called distillation. For two qubit (and qubit-qutrit) systems all entangled states can be distilled and hence are useful for quantum communication. In higher dimensions, there exist the so-called bound entangled states which are entangled but cannot be distilled. They seem to be useless for quantum communication purposes. Nevertheless, they can be activated by an amount of free (disitillable) entanglement.