Berlin 2001 – scientific programme

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Q: Quantenoptik

Q 9: Poster: Quantum Information

Q 9.4: Poster

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

Single-atom multi-photon entanglement mediated by a high-finesse Cavity — •Thomas Legero, Markus Hennrich, Stefan Nussmann, Axel Kuhn, and Gerhard Rempe — Max-Planck-Institut für Quantenoptik, D-85748 Garching

Starting from a proposal of Gheri and Ritsch [1] we investigate the experimental feasibility of an entanglement between the internal states of a single atom and a large number of optical photons.

A single atom strongly coupled to a high-finesse optical cavity allows to control the path of the photons impinging the cavity. This can be achieved with two long-lived atomic states. One of these states leads to reflection of the photons, the other to transmission. If the atom is prepared in a quantum superposition of the two states, an entanglement of atomic state and photon path will be generated.

To show this entanglement, the atom-cavity system should be used as the first beamsplitter of a Mach-Zehnder interferometer. With the path of the photons stored in the internal atomic state, no fringes will be visible at the output ports. However, a suitable measurement performed on the atom allows to erase this “which-way” information, and in correlation with this measurement, the photons detected at the output ports should show interference fringes, which depend on the phase difference of the two paths. Furthermore, we show that the fringe spacing will depend on the number of photons interacting with the atom-cavity system.

[1] K.M. Gheri and H.Ritsch, Phys.Rev.A 56 , 3187 (1997)