Qubit-based detectors for dark matter direct detection

Over the last decade, several low-energy physics searches, including those for particle dark matter, have driven interest in developing increasingly sensitive particle detectors. Superconducting (SC) quantum sensors based on broken Cooper Pairs provide a possible channel for sensing O(meV) energy depositions, and may be a significant step in developing such low-threshold detectors. The Quantum Science Center group at Fermilab is exploring the use of superconducting qubits for particle detection in the LOUD surface dilution fridge facility and the QUIET underground facility. This talk will discuss recent efforts to understand qubit response to energy depositions through a combination of measurements in LOUD and low-energy G4CMP simulations of phonons and Bogoliubov quasiparticles within our superconducting qubit chips. We also show progress on modeling phonon transport in a variety of new materials, as well as ongoing improvements of the superconductor response to energy depositions. We close with a discussion of prospects for measurements within the QUIET facility to understand the impact of reducing ambient backgrounds on qubit performance in the context of dark matter searches.