Berlin 2001 – scientific programme

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Q: Quantenoptik

Q 9: Poster: Quantum Information

Q 9.13: Poster

Tuesday, April 3, 2001, 12:30–15:00, AT2

Towards practical Quantum Cryptography — •Matthäus Halder¹, David Weikersdorfer¹, Patrick Zarda², Christian Kurtsiefer¹, and Harald Weinfurter^1,2 — ¹Sektion Physik der LMU München, Schellingstr. 4/III, 80799 München — ²Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching

Quantum Cryptography bases provable security on fundamental laws of quantum mechanics. It will become the first practical application of quantum communication as soon as compact and stable systems have been developed.

We present first tests of new modules where all optical components necessary for the BB84 protocol are assembled within 5×5 cm². In the sender module (Alice), four pulsed laser diodes (853nm) produce the four necessary polarization states (H,V,+45^∘,-45^∘) and are coupled into a single mode optical fiber. On the other side, the receiver (Bob) analyzes the incoming polarized photons randomly in the (H,V) or (+45^∘,-45^∘) basis without the need for active optical components. Synchronisation between Alice and Bob and polarization control is realized via the quantum channel.

Both modules (including optics and electronics) will find place in compact quantum cryptography modems, or possibly even on pc-cards and will enable fast (keyrate some kHz) quantum key generation.