High-speed phonon imaging using frequency-multiplexed kinetic inductance detectors

We present a measurement of phonon propagation in a silicon wafer utilizing an array of frequency-multiplexed superconducting resonators coupled to a single transmission line. The electronic readout permits fully synchronous array sampling with a per-resonator bandwidth of 1.2 MHz, allowing sub-$\mu$s array imaging. This technological achievement is potentially vital in a variety of low-temperature applications, including single-photon counting, quantum-computing and dark-matter searches.