Darmstadt 2008 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 48: Quanteninformation (Quantenkommunikation)

Q 48.6: Talk

Thursday, March 13, 2008, 17:45–18:00, 1B

Time-Bin Encoding for Narrow-Band Single Photons — •Nils Neubauer, Matthias Scholz, and Oliver Benson — Humboldt-Universität zu Berlin, Institut für Physik, AG Nanooptik, Hausvogteiplatz 5-7, 10117 Berlin

For long-range applications in quantum information processing (e.g., quantum key distribution QKD), time-bin encoding of single photons is the favorable choice since this scheme does not suffer from polarization degradation in optical fibers. In order to build larger quantum networks, coherent storage and retrieval of single photons in atomic ensembles has been suggested and realized, e.g., by using electromagnetically induced transparency in optically dense media. Therefore, the spectrum of these photons needs to match the narrow linewidth of atomic resonances.

We realized a scheme for time-bin encoding of narrow-band single photons. The setup consists of two unbalanced Michelson interferometers acting as encoding and decoding units. Using a relative arm length difference of 100 m each, a path delay of 500 ns can be implemented, suitable for single photons with a bandwidth of 10 MHz. It is intended to show QKD via the BB84 protocol with attenuated light pulses of this bandwidth.