Methods to achieve near-millisecond energy relaxation and dephasing times for a superconducting transmon qubit

TL;DR

This paper demonstrates a superconducting transmon qubit with record-high energy relaxation and dephasing times, significantly advancing qubit coherence for quantum computing.

Contribution

The authors present a high-coherence transmon qubit with unprecedented relaxation and dephasing times, along with detailed design and fabrication methods for reproducibility.

Findings

Median energy relaxation time of 425 microseconds

Maximum dephasing time of 1057 microseconds

Detailed fabrication process enabling high coherence

Abstract

Superconducting qubits are one of the most promising physical systems for implementing quantum computers. However, executing quantum algorithms of practical computational advantage requires further improvements in the fidelities of qubit operations, which are currently limited by the energy relaxation and dephasing times of the qubits. Here, we report our measurement results of a high-coherence transmon qubit with energy relaxation and echo dephasing times surpassing those in the existing literature. We measure a qubit frequency of 2.9 GHz, an energy relaxation time with a median of 425 us and a maximum of (666 +/- 33) us, and an echo dephasing time with a median of 541 us and a maximum of (1057 +/- 138) us. We report in detail our design, fabrication process, and measurement setup to facilitate the reproduction and wide adoption of high-coherence transmon qubits in the academia and industry.