Speaker
Description
Ionizing radiation has been shown to have deleterious effects on superconducting qubit performance, particularly by generating correlated errors in multiple qubits, which is particularly problematic for quantum error correction codes. To better study the effects of ionizing radiation on superconducting qubits and sensors, we have recently installed a dilution refrigerator in the Shallow Underground Laboratory (30 meters-water-equivalent overburden) at Pacific Northwest National Laboratory. The fridge will be augmented with a lead shield designed to reduce the interaction rate from external gammas by greater than 99%. We estimate the residual ionizing radiation interaction rate from the fridge itself and from typical instrumentation hardware. We have assayed the radioactive contaminant levels in samples of superconducting qubits, which were found to be very low in radioactivity, and in common coax connectors and circuit board composites, which we find to substantially dominate the radiation budget. An assessment of required steps to further reduce backgrounds is provided. I will also present some details on a recent publication describing the Geant4 Condensed Matter Physics (G4CMP) software, which simulates charge and phonon transport in crystal substrates and transduction into quasiparticle production in superconducting films.
| Submitted on behalf of a Collaboration? | No |
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