Speaker
Description
Microwave SQUID Multiplexers enable the simultaneous readout of many micro-calorimeter detectors through the use of frequency domain multiplexing via superconducting resonators inductively coupled to RF-SQUIDs. These resonators are frequency modulated through flux-ramp modulation, which sets the effective sampling rate of the detector. The slew rate of the modulation is primarily limited by the resonator ring-up time and the flyback transient of non-ideal flux ramps. Accurate time-domain simulations of resonators coupled to SQUIDs would push the limit of detector sample rates and allow fast design iteration of multiplexer devices.
We present an open-source, python-based framework to simulate the time-domain response of resonator-SQUID channels. This framework is built on a semi-classical Input-Output theory, equivalent to a classical Coupled-Mode Theory, but motivated from the Hamiltonian perspective. We validate this framework against a NIST multiplexer device, operated in a Maybell dilution refrigerator. We demonstrate reproduction of the steady-state S21 spectrum and power-dependent effects, and accurately predict the time-domain response with flux-ramp frequencies above 1MHz. This simulation framework provides an understanding of the fast time response of resonators coupled to SQUIDs, and enables the multiplexed readout of cryogenic detectors to be pushed to microsecond limits.