Fast Reset and Suppressing Spontaneous Emission of a Superconducting Qubit

TL;DR

This paper introduces a circuit design that significantly reduces spontaneous emission in superconducting qubits, enabling fast, high-fidelity qubit reset and tunable lifetime control, advancing quantum computing capabilities.

Contribution

The authors develop a circuit design that suppresses spontaneous emission while maintaining strong coupling, with experimental validation showing tunable qubit lifetime and rapid reset.

Findings

Qubit relaxation times match circuit model predictions.

Qubit lifetime can be tuned over a factor of 50.

Achieved 99.9% fidelity in 120 ns qubit reset.

Abstract

Spontaneous emission through a coupled cavity can be a significant decay channel for qubits in circuit quantum electrodynamics. We present a circuit design that effectively eliminates spontaneous emission due to the Purcell effect while maintaining strong coupling to a low-Q cavity. Excellent agreement over a wide range in frequency is found between measured qubit relaxation times and the predictions of a circuit model. Using fast (nanosecond time-scale) flux biasing of the qubit, we demonstrate in situ control of qubit lifetime over a factor of 50. We realize qubit reset with 99.9% fidelity in 120 ns.