Heralded storage of photonic polarization in a single atom

6 05/2014

Tuesday, 06 May. 2014, 15:00 - 16:00

Presenter: Norbert Kalb; MPQ, Garching, Germany
Host: M. Aspelmeyer
Where: Schrödingerroom, 4th floor, Boltzmanngasse 5, 1090 Wien

The long-distance communication of quantum information requires an interface that provides the ability to faithfully send and receive this type of information. I will report on the realization of quantum-state mapping between the polarization of a photon and the spin state of a single atom, which is trapped at the center of an optical cavity in the strong coupling regime. The implemented storage scheme is both heralded and conceptually deterministic. The storage protocol comprises three steps: First, the atomic state is prepared in a specific superposition of Zeeman levels in the ground-state manifold. Second, a faint laser pulse is reflected off the atom-cavity system which realizes a state-dependent phase shift of the combined atom-photon state. Third, detection of a reflected photon heralds a successful storage event with a demonstrated efficiency of 39%. The inverse process, read-out of the atomic state, is realized by the reflection of a faint laser pulse and subsequent measurement of the atomic state. The quantum mechanical character of both processes is proven by fidelities of 86% and 88% respectively, which is well above the classical boundary. The demonstrated novel approach to optical quantum memory opens new perspectives towards distributed quantum computation and quantum communication.