Progress in using resonator coupled transmons for phonon-mediated particle detection

Phonon-mediated superconducting qubits are a novel class of proposed rare-event search detectors, potentially capable of resolving meV energy deposits from coherent elastic neutrino-nucleus scattering events within a crystalline target. The SONIQ (Sensing of Neutrinos in Qubits) collaboration is seeking to build a sub-eV threshold sensor coupled to a kilogram of germanium. One promising sensor architecture for this project is that of a planar weakly charge-sensitive transmon coupled to a lumped element resonator. Phonons generated by neutrino interactions with the substrate modify the quasiparticle density within the transmon's pads, affecting the charge-parity of the device. This dynamic parity switching can be measured and thus gives a means to quantify the nature of the initial energy deposition. We report on initial data taken with our first aluminum-on-silicon devices on their response to photon and x-ray sources. Furthermore, we detail future advances including changes to fabrication, resonator design, and our proposed use of low Tc material for increased sensitivity.