Ultrahigh finesse Fabry-Perot superconducting resonator
  We have built a microwave Fabry-Perot resonator made of diamond-machined copper mirrors coated with superconducting niobium. Its damping time (Tc = 130 ms at 51 GHz and 0.8 K) corresponds to a &#64257;nesse of 4.6 x 109, the highest ever reached for a Fabry-Perot in any frequency range. This result opens novel perspectives for quantum information, decoherence and non-locality studies. 
Stefan Kuhr, S\'ebastien Gleyzes (LKB - Lhomond), Christine Guerlin   (LKB - Lhomond), Julien Bernu (LKB - Lhomond), Ulrich ...