Error per single-qubit gate below $10^{-4}$ in a superconducting qubit

TL;DR

This paper demonstrates single-qubit gates in a superconducting transmon qubit with error rates below 10^{-4}, achieving high fidelity essential for reliable quantum computing.

Contribution

The work fabricates a transmon qubit with long coherence times and achieves record low single-qubit gate errors below 10^{-4}, advancing quantum gate fidelity.

Findings

Average gate error below 10^{-4} achieved

Error budget includes decoherence and leakage errors

Non-Markovian behavior observed in long-sequence GST

Abstract

Implementing arbitrary single-qubit gates with near perfect fidelity is among the most fundamental requirements in gate-based quantum information processing. In this work, we fabric a transmon qubit with long coherence times and demonstrate single-qubit gates with the average gate error below $10^{-4}$, i.e. $(7.42\pm0.04)\times10^{-5}$ by randomized benchmarking (RB). To understand the error sources, we experimentally obtain an error budget, consisting of the decoherence errors lower bounded by $(4.62\pm0.04)\times10^{-5}$ and the leakage rate per gate of $(1.16\pm0.04)\times10^{-5}$. Moreover, we reconstruct the process matrices for the single-qubit gates by the gate set tomography (GST), with which we simulate RB sequences and obtain single-qubit fedlities consistent with experimental results. We also observe non-Markovian behavior in the experiment of long-sequence GST, which may provide guidance for further calibration. The demonstration extends the upper limit that the average fidelity of single-qubit gates can reach in a transmon-qubit system, and thus can be an essential step towards practical and reliable quantum computation in the near future.