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Q: Quantenoptik

Q 9: Quanteneffekte 1

Q 9.4: Vortrag

Montag, 24. März 2003, 14:45–15:00, F107

Quantum interference of independently generated single photons — •T. Legero, T. Wilk, A. Kuhn, and G. Rempe — Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany

The feasibility of linear-optical quantum computation [1] depends on the availability of a triggered source of indistinguishable single photons. The source can be tested by performing a second-order interference experiment, where two single-photon wavepackets are superposed on a 50/50 beam splitter [2]. If the photons are indistinguishable, they both leave the beam splitter in the same direction. Therefore the cross-correlation of the photo currents of two detectors monitoring the two output ports of the beam splitter vanishes for perfect overlap of the two photons, while differences in the polarization, spatial, temporal or spectral mode of the two photons lead to a non-vanishing cross-correlation.

We discuss an experiment where consecutive single-photon wavepackets from a cavity-QED source [3] interfere at the second beam splitter of a Mach-Zehnder interferometer. One arm of the interferometer has a 1100 m long optical fiber to delay the photons in such a way that subsequently emitted photons overlap at the output beam splitter. Perfect temporal overlap is obtained if the pulse rate of the source matches the fiber length. First experimental results show a reduced cross-correlation, as expected for indistinguishable photons.

[1] Knill et al. Nature 409, 46 (2001)

[2] Hong et al. PRL 59, 2044 (1987); Santori et al. Nature 419, 594 (2002)

[3] Hennrich et al. PRL 85, 4872 (2000); Kuhn et al. PRL 89, 67901 (2002)