Excitation of quasiparticle pairs in superconducting nanodevices by 1/f noise

Abstract

Superconducting nanodevices such as qubits, resonators, and photodetectors, have revolutionized our capabilities for probing and controlling quantum phenomena. Nonequilibrium quasiparticles, which are broken Cooper pairs that cause decoherence and energy loss, can limit their performance. The number of these quasiparticles is often tens of orders of magnitude greater than would be present in thermal equilibrium. Background radiation has been shown to excite quasiparticles, but quasiparticles are observed even when the devices are carefully shielded. Here we show that the high-frequency components of 1/f noise can excite quasiparticle pairs and that this mechanism is consistent with previously unexplained experimental results. We also propose new experiments that exploit this quasiparticle excitation mechanism to non-invasively characterize high-frequency charge noise as well as the locations and nature of the defects producing the noise. The proposed experiments would also investigate how this noise changes as the defects that give rise to it evolve towards thermal equilibrium.