Düsseldorf 2007 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 47: Quanteninformation (Quantenkommunikation)

Q 47.8: Talk

Wednesday, March 21, 2007, 18:15–18:30, 5L

Experimental realisation of a quantum communication protocol using entangled photons — •Nino Walenta and Martin Ostermeyer — Universität Potsdam, Institut für Physik, 14469 Potsdam

Quantum cryptography protocols using entangled qubit pairs can increase the rate and security of information exchange. The ping pong coding scheme based on entangled photons allows asymptotically secure key distribution and, theoretically, quasi secure direct communication, too [1]. In this presentation we show the experimental realisation of this communication protocol.

Polarisation-entangled photon pairs are generated by parametric down conversion with ps laser pulses. Two out of 4 Bell states are used in order to represent two bits of information. The information is encoded by switching between these two states via the unitary transformation of a Pockels cell applied to one of the photons. The two Bell states are distinguished by a modified Bell state analysis evaluating the arrival time and also the polarisation of the photons. The detection time of every photon is analysed using time-correlated single photon counting (TCSPC) modules in time-tag mode for every detector.

[1] K. Boström, T. Felbinger, Phys. Rev. Lett. 89, 187902 (2002)