Measuring TKID Responsivity with Photon Shot Noise

Presenter(s)

Elizabeth Berzin

Abstract or Description

Thermal Kinetic Inductance Detectors (TKIDs) are cryogenic bolometers that measure incident power through resonant frequency shifts in a superconducting micro-resonator. Currently, TKIDs are designed with external circuitry used to bias a resistive heater to simulate optical loading for calibration measurements. This additional circuitry defeats much of the multiplexing benefit introduced by TKIDs. Here, we explore a method of measuring TKID responsivity with photon shot noise, with the goal of removing the need for the existing heaters. Similar to the process by which CCD cameras calibrate gain by exploiting the Poisson statistics of photon counts, we use the power proportionality of photon NEP to estimate responsivity. We demonstrate through modeling and experimental results that this method is sensitive to systematic errors, such as chip heating and direct quasiparticle production, and discuss strategies for mitigating these effects. We also compare our measurements to models of NEF, quasiparticle lifetime, and frequency shift.