Suppressing Qubit Errors via Local Tuning of Two-Level System Defects

The performance of large scale quantum processors depends not only on the instantaneous performance of their constituent qubits but also on their stability over time. In superconducting qubit systems, this stability is often threatened by the presence of two-level system (TLS) defects that exhibit both spectral and temporal fluctuations. As these TLS defects come into and out of resonance with the qubit frequency, they can cause a fluctuating reduction in qubit energy relaxation times. One common method for mitigating these effects involves regularly re-optimizing the qubit frequencies on a quantum processor to avoid these TLS defects; however, this is often a highly constrained problem since the qubit frequencies can also affect single- and two-qubit gate performance. Instead, we demonstrate a method to locally tune the frequency of TLS defects on a multi-qubit device. We show how this can improve energy relaxation times and reduce system instability over time, without the need for continuous recalibration of qubit frequencies and gate parameters.