Abstract

A single atom trapped at the center of a high-finesse optical cavity is an ideal starting point for studying the coherent interaction between light and matter. At the same time, it provides great possibilities for quantum information processing, exemplified by our demonstration of efficient, lossless hyperfine state detection based on the Purcell effect [1]. Making use of the rich level structure of 87Rb, it is possible to go beyond the Jaynes-Cummings physics. A three-level system in a lambda configuration inside the cavity allows for the efficient generation of single photons with their temporal, spectral and polarization properties accurately controlled. This allows for the generation of atom-photon and photon-photon entanglement, an ideal starting point for the realization of a distributed quantum network. Quantum interference in the amplitudes of the two optical transitions can lead to electromagnetically induced transparency (EIT), where the presence of a weak control beam drastically alters the optical properties of the medium. Inside an optical cavity, this effect is highly enhanced and we have observed it for a few and even single atoms [2]. The high electric field per photon should allow for nonlinear interactions between single photons mediated by single atoms, which is appealing for future applications in quantum information processing.

[1] J. Bochmann et al., Phys. Rev. Lett. 104, 203601 (2010) [2] M. Mücke et al., Nature 465, 755 (2010)