Optimal Demodulation Domain for Microwave SQUID Multiplexers in Presence of Readout System Noise

TL;DR

This paper investigates the optimal demodulation domain for microwave SQUID multiplexers, considering various noise sources and readout configurations, to enhance system noise performance prediction and noise engineering.

Contribution

It extends simulation frameworks to include noise sources and evaluates optimal readout parameters for minimal system noise in microwave SQUID multiplexers.

Findings

Optimal parameters identified for minimum noise in different demodulation domains.

System noise sensitivity analyzed for additive and multiplicative noise sources.

Case study demonstrates improved noise prediction for SDR readout systems.

Abstract

The Microwave SQUID Multiplexer ({\mu}MUX) is the device of choice for the readout of a large number of Low-Temperature Detectors in a wide variety of experiments within the fields of astronomy and particle physics. While it offers large multiplexing factors, the system noise performance is highly dependent on the cold and warm-readout electronic systems used to read it out, as well as the demodulation domain and parameters chosen. In order to understand the impact of the readout systems in the overall detection system noise performance, first we extended the available {\mu}MUX simulation frameworks including additive and multiplicative noise sources in the probing tones (i.e. phase and amplitude noise), along with the capability of demodulating the scientific data, either in resonator's phase or scattering amplitude. Then, considering the additive noise as a dominant noise source, the optimum readout parameters to achieve minimum system noise were found for both open-loop and flux-ramp demodulation schemes in the aforementioned domains. Later, we evaluated the system noise sensitivity to multiplicative noise sources under the optimum readout parameters. Finally, as a case study, we evaluated the optimal demodulation domain and expected system noise level for a typical Software-Defined Radio (SDR) readout system. This work leads to an improved system performance prediction and noise engineering based on the available readout electronics and selected demodulation domain.