In-situ electro-optic sampling of microwave signals under cryogenic conditions and for superconducting applications

TL;DR

This paper presents a cryogenic electro-optic sampling system capable of measuring microwave signals on cryogenic superconducting devices, enabling quantum-standard traceable measurements and analysis of superconducting transmission line properties.

Contribution

The work introduces a cryogenic EOS setup integrated with a quantum-accurate microwave source, enabling precise, traceable measurements of superconducting microwave components and signals.

Findings

Successful measurement of microwave signals at cryogenic temperatures.

Calibration of the EOS setup with a quantum-accurate source.

Analysis of superconducting transmission line responses and reflections.

Abstract

We demonstrate a cryogenic electro-optic sampling (EOS) setup that allows for the measurement of microwave signals at arbitrary positions on a cryogenic chip-scale device. We use a Josephson Arbitrary Waveform Synthesizer (JAWS) to generate quantum-accurate voltage signals and measure them with the EOS setup, allowing for the calibration of its response, yielding traceability of the microwave measurements to a quantum standard. We use the EOS setup to determine the time-domain response of ultrafast cryogenic photodiodes and the electrical reflection coefficient, i.e., the S11 scattering parameter, in a superconducting transmission line. Finally, we introduce an optical femtosecond pulse source which can be used to study the fidelity of superconducting transmission lines and terminations, as well as reflections from elements like Josephson junction arrays imbedded in them.