Characterizing decoherence rates of a superconducting qubit by direct microwave scattering

TL;DR

This paper experimentally measures and characterizes the decoherence and decay rates of a superconducting qubit coupled to an open transmission line, providing insights into non-radiative decay and pure dephasing in a resonator-free environment.

Contribution

It introduces a comprehensive method to directly measure and distinguish decay and dephasing rates of superconducting qubits without a resonator, enhancing decoherence benchmarking techniques.

Findings

Pure dephasing rate is an order of magnitude smaller than non-radiative decay.

Consistent decay and decoherence rates were obtained across multiple measurement methods.

The study demonstrates a pathway for benchmarking qubit decoherence in open transmission line setups.

Abstract

We experimentally investigate a superconducting qubit coupled to the end of an open transmission line, in a regime where the qubit decay rates to the transmission line and to its own environment are comparable. We perform measurements of coherent and incoherent scattering, on- and off-resonant fluorescence, and time-resolved dynamics to determine the decay and decoherence rates of the qubit. In particular, these measurements let us discriminate between non-radiative decay and pure dephasing. We combine and contrast results across all methods and find consistent values for the extracted rates. The results show that the pure dephasing rate is one order of magnitude smaller than the non-radiative decay rate for our qubit. Our results indicate a pathway to benchmark decoherence rates of superconducting qubits in a resonator-free setting.