Hannover 2003 – wissenschaftliches Programm

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Q: Quantenoptik

Q 50: Quantenkommunikation

Q 50.2: Vortrag

Freitag, 28. März 2003, 14:15–14:30, F102

Distribution of entangled Gaussian states over large distances and feasible quantum privacy amplification — •Jens Eisert¹, Stefan Scheel², Daniel E. Browne², and Martin B. Plenio² — ¹Universität Potsdam, Institut für Physik, An Neuen Palais 10, 14469 Potsdam — ²Quantum Optics and Laser Science, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, UK

Quantum information over continuous variables offers a promising alternative to its finite-dimensional counterpart. Many applications rely on the distribution of entangled Gaussian states to distinct locations. Unfortunately, decoherence will typically reduce the degree of entanglement significantly. Very recently, it turned out that by means of Gaussian operations only, this process cannot be effectively reversed, as distillation with Gaussian operations is not possible. This talk will be concerned with a feasible solution of this indeed crucial problem: with a single initial non-Gaussian step, one can retrieve entangled Gaussian states in an iterative procedure using only tools that are available with present technology. The same method, referred to as ’Gaussification procedure’, can be used to purify a supply of entangled mixed states, such that the resulting states can not be entangled with a third party any more. This observation gives rise to a feasible procedure for quantum privacy amplification in quantum cryptography.