Speaker
Description
The superconducting quasiparticle-amplifying transmon (SQUAT) sensor architecture has been demonstrated as a weakly charge sensitive qubit with resonator-free readout to continuously monitor the quasiparticle-tunelling-dependent parity of the qubit ground state. SQUATs are designed to be sensitive to both meV-scale phonons and THz photons, the former of which will be the focus of this talk.
Using a cryogenic MEMS scanning assembly capable of maneuvering a beam of optical light around the backside of a silicon chip, we can generate a source of pair-breaking phonons in the substrate below several SQUATs and observe the sensor response to this phonon source. Continuous wave measurements have revealed spatial dependence in the quasiparticle tunneling rate which closely resembles the phonon caustics expected for (100) silicon. Preliminary pulsed measurements are also ongoing to determine a representative pulse template for SQUATs. I will also discuss ongoing fabrication efforts in the SLAC Detector Microfabrication Facility (DMF) to leverage different materials and substrates for future SQUAT designs.