München 2004 – wissenschaftliches Programm

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Q: Quantenoptik und Photonik

Q 45: Quanteninformation IV

Q 45.1: Gruppenbericht

Freitag, 26. März 2004, 11:00–11:30, HS 101

Entanglement of a single photon with an atom-cavity system — •T. Legero, T. Wilk, M. Hennrich, A. Kuhn, and G. Rempe — Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany

The coalescence of two identical photons superposed on a 50/50 beamsplitter is a well known effect [1], for which a time resolved analysis reveals that it can also be interpreted as a measurement induced entanglement, followed by an interferometric verification. Because the beamsplitter conceals the origin of the first detected photon, the remaining photon is projected into a path-entangled state [2]. We apply this effect to entangle a single atom with a single photon, and to determine degree and lifetime of the entanglement.

A strongly coupled atom-cavity system generates two successive single-photon wave packets which are long compared to the time resolution of our detectors [3]. The first photon is sent into a 1100 m long optical fiber and impinges on a beamsplitter simultaneously with the second photon that travels along a negligibly short path. Since the coherence time exceeds the photon transit time from the source to the beamsplitter, the first photodetection induces an entanglement between the photonic field mode of the fiber and the state of the source atom. This entanglement is verified in a correlation experiment where the phase of the superposition state is changed in a controlled manner.

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

[2] Legero et al.Appl.Phys.B 77, 797 (2003)

[3] Kuhn et al.PRL 89, 67901 (2002)