First Measurements of Superconducting Quasiparticle-Amplifying Transmon (SQUAT) Sensors for THz Photons and meV Phonons

SQUATs are new quantum sensor based on a transmon qubit architecture that can detect THz photons or meV phonons. Incoming particles deposit energy in the qubit islands, generating quasiparticles, which can be detected as they tunnel across the qubit junction as a shift in the qubit parity state. These devices have several features which are especially beneficial for dark matter searches, including excellent energy sensitivity, bandwidth; multiplexability, and noise performance. Here we present the design and initial measurements of prototype SQUAT devices and demonstrate the potential of this new sensor.