1202.0816 (P. J. de Visser et al.)

Microwave-induced excess quasiparticles in superconducting resonators
measured through correlated conductivity fluctuations    [PDF]

P. J. de Visser, J. J. A. Baselmans, S. J. C. Yates, P. Diener, A. Endo, T. M. Klapwijk

We have measured the number of quasiparticles and their lifetime in aluminium
superconducting microwave resonators. The number of excess quasiparticles below
160 mK decreases from 75 to 18 $\mu$m$^{-3}$ with a 6 dB decrease of the
microwave power. The quasiparticle lifetime increases accordingly from 1.4 to
3.6 ms. These properties of the superconductor were measured through the
spectrum of correlated fluctuations in the quasiparticle system and condensate
of the superconductor, which show up in the resonator amplitude and phase
respectively. Because uncorrelated noise sources vanish, fluctuations in the
superconductor can be studied with a sensitivity close to the vacuum noise.

View original: http://arxiv.org/abs/1202.0816