Storage and control of optical photons using Rydberg polaritons
  We use a microwave field to control the quantum state of optical photons stored in a cold atomic cloud. The photons are stored in highly excited collective states (Rydberg polaritons) enabling both fast qubit rotations and control of photon-photon interactions. Through the collective read-out of these pseudo-spin rotations it is shown that the microwave field modifies the long-range interactions between polaritons. This technique provides a powerful interface between the microwave and optical domains, with applications in quantum simulations of spin liquids, quantum metrology and quantum networks. 
D. Maxwell, D. J. Szwer, D. P. Barato, H. Busche, J. D. Pritchard, A.   Gauguet, K. J. Weatherill, M. P. A. Jones and C. S. ...
quant-ph physics.atom-ph