Transmon qubit with relaxation time exceeding 0.5 milliseconds

TL;DR

This paper reports a transmon qubit with a record relaxation time exceeding 0.5 milliseconds, achieved through a tantalum dry etching process, and compares material effects on qubit performance.

Contribution

Demonstrates a high-coherence transmon qubit using tantalum with a novel dry etching process and compares material impacts on qubit relaxation and coherence times.

Findings

Tantalum transmon achieved T1 of 503 microseconds.

Tantalum outperformed niobium and aluminum in qubit performance.

Oxide loss at the metal-air interface affects qubit relaxation times.

Abstract

By using the dry etching process of tantalum (Ta) film, we had obtained transmon qubit with the best lifetime (T1) 503 us, suggesting that the dry etching process can be adopted in the following multi-qubit fabrication with Ta film. We also compared the relaxation and coherence times of transmons made with different materials (Ta, Nb and Al) with the same design and fabrication processes of Josephson junction, we found that samples prepared with Ta film had the best performance, followed by those with Al film and Nb film. We inferred that the reason for this difference was due to the different loss of oxide materials located at the metal-air interface.