Minimizing quasiparticle generation from stray infrared light in superconducting quantum circuits

We find that quasiparticle generation from stray infrared light creates a significant loss mechanism in superconducting resonators and qubits. We show that resonator quality factors and qubit energy relaxation times are limited by a quasiparticle density of approximately 200 mu m(-3), induced by 4 K blackbody radiation from the environment. We demonstrate how this influence can be fully removed by isolating the devices from the radiative environment using multistage shielding. (C) 2011 American Institute of Physics. [doi:10.1063/1.3638063]