Energy relaxation time fluctuations in transmon qubits with different superconducting gaps
Superconducting qubits are an ideal platform for quantum computing and the relaxation time T1 has increased in recent years. We have repeatedly measured the behavior of Al/AlOx/Al transmons that have electrodes with different superconducting gaps in a 3-D cavity and observed significant fluctuations. In our devices, the base electrode was formed from nominally pure aluminium while the counter electrode was formed from oxygen-doped aluminium. The measurement of T1 varied from 100 to 300 μs under low temperature and the maximum T1 of the transmon observed was 310 μs at 20 mK. A device with a thin doped-Al base electrode and thick pure Al counter electrode showed T1 fluctuations of a similar size with maximum T1 values over 200 μs. Measurements of the fluctuations versus temperature reveal that the standard deviation of T1 is proportional to T1. I proposed a mechanism for exploring the T1 fluctuation data and discuss the possible underlying cause of the T1 fluctuations.
Livestream the event on Zoom (Yale login required)