Konstanz 1998 – wissenschaftliches Programm

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Q: Quantenoptik

Q 22: Symposium Quantenkommunikation II

Q 22.3: Vortrag

Mittwoch, 18. März 1998, 14:45–15:00, R 711

N-photon source for quantum communication — •P. Törmä, J. I. Cirac, K. M. Gheri, C. Saavedra, and P. Zoller — Institut für Theoretische Physik, Technikerstrasse 25, 6020 Innsbruck, Austria

A controlled source of entangled single qubits is necessary for most quantum communication procedures. We propose a cavity QED -scheme to generate in a controlled manner a sequence of strongly entangled single photon wave packets. The photons are generated inside a cavity by laser-atom interaction, in which the atomic initial state is mapped on the photon state. After a sufficiently long time the photon has leaked out of the cavity, and the process can be repeated for the next qubit. Since no measurement is performed on the atom in between, the qubits will be entangled. The qubits can be generated in our scheme at a controlled rate, whereas techniques such as down conversion in crystals produce entangled photon pairs at random times. Moreover, our scheme is not limited to the generation of pairs: the production of multi-qubit entangled states, such as the GHZ-states, is straightforward. Also the shape of the photon wavepacket is under control. Here we present the general results and discuss specific examples related to teleportation and cryptography.