Abstract

We have realised the controlled entanglement of two circular Rydberg atoms through their common interaction with an off-resonant superconducting microwave resonator. The method follows a proposal by S.-B. Zheng and G.-C. Guo [1]. One atom is prepared in the ground state |g〉 and the other in the excited state |e〉. The g ⟹ e transition (51.1 GHz) is close to resonance with the cavity mode. The resulting initial state |g〉⊗|e〉 is coupled, via second order non-resonant interaction with the cavity, to the degenerate state |e〉⊗|g〉. A cyclic and coherent energy exchange between the atoms (Rabi oscillation) therefore takes place. At variance with previous related experiments [2], the photon mediating the atom-atom interaction is only virtually exchanged and has not to be stored in the cavity, whose quality factor becomes unimportant. We show however that the presence of the cavity field mode largely enhances the probability of an energy exchange between the atoms as compared with the effect of direct dipole-dipole interaction in free space. By choosing properly the interaction parameters, we have prepared a maximally entangled pair of atoms.

© 2001 EPS