Title: 

Unconventional readout and control techniques for kinetic inductance detectors

Abstract:

Superconducting sensors are ubiquitous in telescopes operating at millimetre- and submillimetre-wavelengths. With the preeminent detector technology in the field, the transition-edge sensor, already achieving the fundamental per-detector sensitivity limit, improvements in instrument performance must instead come from fielding higher numbers of detectors in an array. This has been a motivating factor in the expansion of the use of another detector technology, the kinetic inductance detector (KID), a superconducting resonator detector which promises simplified cryogenics, high multiplexing density, and greater design flexibility in comparison with established transition-edge sensor arrays.

A new generation of KID instruments has been accompanied by the development of a new generation of readout technology to operate them. While working on the readout for a prototype on-chip KID spectrometer for the South Pole Telescope, we applied these new systems to the study of the detectors themselves. While typical resonator characterization is performed using single-tone sequential frequency sweep measurements, the multi-tone architecture of the readout system can instead make simultaneous multi-frequency measurements across the bandwidth of a single device. This has enabled previously-inaccessible views of resonator behaviour, and allowed us to demonstrate control of a KID’s resonant frequency by digitally modulating a readout tone. This type of active electro-quasiparticle feedback alleviates operational concerns such as resonator collisions and intermodulation distortion. 

Presently in an early stage of development, the use of this system with large-scale KID arrays will facilitate higher multiplexing factors and simplified on-sky operation, improving the performance of these detectors in the context of millimetre and submillimetre astronomy.