Controlling the Spontaneous Emission of a Superconducting Transmon Qubit
Andrew Houck, J. A. Schreier, Blake Johnson, Jerry M. Chow, Jens Koch, Jay Gambetta, David Schuster, Luigi Frunzio, Michel Devoret, S. M. Girvin, Robert J. Schoelkopf · Physical Review Letters · 2008
We present a detailed characterization of coherence in seven transmon qubits in a circuit QED architecture. We find that spontaneous emission rates are strongly influenced by far off-resonant modes of the cavity and can be understood within a semiclassical circuit model. A careful analysis of the spontaneous qubit decay into a microwave transmission-line cavity can accurately predict the qubit lifetimes over 2 orders of magnitude in time and more than an octave in frequency. Coherence times T1 and T_{2};{*} of more than a microsecond are reproducibly demonstrated.