Loss and decoherence due to stray infrared light in superconducting   quantum circuits
  We find that stray infrared light from the 4 K stage in a cryostat can cause significant loss in superconducting resonators and qubits. For devices shielded in only a metal box, we measured resonators with quality factors Q = 10^5 and qubits with energy relaxation times T_1=120 ns, consistent with a stray light-induced quasiparticle density of 170-230 \mu m^{-3}. By adding a second black shield at the sample temperature, we found about an order of magnitude improvement in performance and no sensitivity to the 4 K radiation. We also tested various shielding methods, implying a lower limit of Q = 10^8 due to stray light in the light-tight configuration. 
R. Barends, J. Wenner, M. Lenander, Y. Chen, R. C. Bialczak, J. Kelly,   E. Lucero, P. O'Malley, M. Mariantoni, D. Sank, H. ...
cond-mat.mes-hall cond-mat.supr-con quant-ph