TLS induced decoherence instabilities in superconducting qubits

We study the temporal stability of relaxation and dephasing in superconducting transmon qubits. By collecting statistics during measurements spanning multiple days, we reveal large fluctuations of qubit lifetimes and find that the main cause of T₁ fluctuations is interacting parasitic two-level-systems (TLS). Our statistical analysis also provides useful information about dynamics of TLS which could help identify possible microscopic sources of TLS, which still remain elusive. Moreover, interacting TLS also cause capacitance fluctuations, ultimately leading to frequency noise and dephasing of the qubit state. These discoveries are important for manufacturing stable superconducting circuits suitable as a scalable quantum computing platform where drift and fluctuations lead to unnecessary calibration and downtime.