Characterizing superconducting quantum circuits at a deep-underground facility

Correlated errors and fluctuations in qubit properties, including coherence times, may limit the realization of fault-tolerant quantum computing. Recent experiments with superconducting qubits reported ionizing radiation, from cosmic rays or terrestrial sources, impacting the performance of superconducting qubits. Sudbury Neutrino Observatory Laboratory (SNOLAB), one of the world’s deepest underground laboratories, provides an environment with both extremely low cosmic radiation and exceptionally low terrestrial radiation levels. In collaboration with SNOLAB, we aim to perform advanced characterizations of the impact of ionizing radiation on superconducting qubits and resonators by comparing measurements obtained at different test sites, both underground and above-ground. The collaboration has completed an upgrade of the Cryogenic Underground TEst facility (CUTE) at SNOLAB to enable standard superconducting qubit measurements. This included performing radioactivity assays of standard microwave components typically used for qubit measurements. We have completed our first measurements of qubits and resonators underground at SNOLAB, and will continue with further characterizations. We present preliminary results from the work.