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 finesse 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.
@article{arxiv.quant-ph/0612138,
title = {Ultrahigh finesse Fabry-Perot superconducting resonator},
author = {Stefan Kuhr and Sébastien Gleyzes and Christine Guerlin and Julien Bernu and Ulrich Busk Hoff and Samuel Deléglise and Stefano Osnaghi and Michel Brune and Jean-Michel Raimond and Serge Haroche and E. Jacques and P. Bosland and B. Visentin},
journal= {arXiv preprint arXiv:quant-ph/0612138},
year = {2007}
}