Using Qubit-Derived Sensors to Design Radiation Mitigation Techniques

In this talk I will discuss ongoing efforts in the Dark Matter/Quantum Information Science (DMQIS) group at SLAC at the convergence of quantum sensing and quantum computing. Our group is focused on three main channels by which qubits can be corrupted by radiation: photon-induced poisoning from environmental radiation; phonon-induced poisoning contributing to elevated quasiparticle temperatures; and charge-coupled poisoning due to reconfiguration of substrate charge during high-energy impact events. We are developing a sensor called the Superconducting Quasiparticle-Amplifying Transmon (SQUAT), a resonator-free superconducting qubit which can be probed with a broad range of readout techniques at high bandwidth. This sensor combines charge sensitivity, high phonon collection efficiency, and tunable dipole radiation sensitivity, and provides a robust design language to target detection of a range of radiation backgrounds. The enhanced coupling to relevant radiation backgrounds allows for higher fidelity probes of quasiparticle poisoning sources and charge-related TLS drift. In this talk I will compare and contrast SQUAT performance and lessons learned thus far with observed behavior in convention qubits, and discuss the path forward for integrating these and related sensors into quantum computing platforms moving forward. I will also discuss new calibration tools and simulations we are helping to develop (G4CMP) to build out a toolkit for robust design of radiation-hardened qubits.