Speaker: Haonan Xiong
Advisor: V. Manucharyan
Speaker 2: Rui Zhang
Title: Unexpected Behavior of Transmon Relaxation Due to Non-Equilibrium Quasiparticles
Understanding and decreasing the energy relaxation rate of transmon qubits is important for their use as qubits. One known source of relaxation is non-equilibrium quasiparticles. We have measured the relaxation time T1 of Al/AlOx/Al transmons mounted in a 3D aluminum cavity and have found that T1can increase by as much as a factor of two (up to 90 us) when increasing the temperature of the device from 20 mK to 100 mK. We will discuss our results and compare them to a model based on the behavior of non-equilibrium quasiparticles residing in regions of the transmon with slightly different superconducting energy gaps. Fits to the model allow us to extract key parameters such as the values of the superconducting energy gap and density of non-equilibrium quasiparticles in each region.