Controlled DC Monitoring of a Superconducting Qubit

TL;DR

This paper demonstrates controlled DC monitoring of a superconducting transmon qubit using a semiconductor FET, revealing how gate-controlled environmental coupling affects qubit relaxation.

Contribution

It introduces a method to compare qubit and transport properties within the same device and models the influence of DC monitoring on qubit relaxation.

Findings

Monitoring circuit affects qubit relaxation rate

Gate-controlled environmental coupling influences qubit coherence

Model accurately predicts experimental relaxation behavior

Abstract

Creating a transmon qubit using semiconductor-superconductor hybrid materials not only provides electrostatic control of the qubit frequency, it also allows parts of the circuit to be electrically connected and disconnected in situ by operating a semiconductor region of the device as a field-effect transistor (FET). Here, we exploit this feature to compare in the same device characteristics of the qubit, such as frequency and relaxation time, with related transport properties such as critical supercurrent and normal-state resistance. Gradually opening the FET to the monitoring circuit allows the influence of weak-to-strong DC monitoring of a live qubit to be measured. A model of this influence yields excellent agreement with experiment, demonstrating a relaxation rate mediated by a gate-controlled environmental coupling.