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

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 72 to 17??m?3 with a 6?dB decrease of the microwave power. The quasiparticle lifetime increases accordingly from 1.4 to 3.5?ms. These properties of the superconductor...

Minimal resonator loss for circuit quantum electrodynamics

We report quality factors of up to 500x10³ in superconducting resonators at the single photon levels needed for circuit quantum electrodynamics. This result is achieved by using NbTiN and removing the dielectric from regions with high electric fields. As demonstrated by a comparison with Ta, the crucial sources of intensity-dependent loss are...