On the fragility of gate-error metrics in simulation models of flux-tunable transmon quantum computers

TL;DR

This paper examines how gate-error metrics in flux-tunable transmon quantum computers are influenced by modeling assumptions, how errors accumulate over multiple gates, and their effectiveness in predicting overall device performance.

Contribution

It provides a detailed analysis of the fragility of gate-error metrics and their limitations in predicting cumulative errors in realistic quantum computer models.

Findings

Gate-error metrics are sensitive to model assumptions.

Errors over consecutive gates do not accumulate linearly.

Gate-error metrics poorly predict overall device performance.

Abstract

Constructing a quantum computer requires immensely precise control over a quantum system. A lack of precision is often quantified by gate-error metrics, such as the average infidelity or the diamond distance. However, usually such gate-error metrics are only considered for individual gates, and not the errors that accumulate over consecutive gates. Furthermore, it is not well known how susceptible the metrics are to the assumptions which make up the model. Here, we investigate these issues using realistic simulation models of quantum computers with flux-tunable transmons and coupling resonators. Our main findings reveal that (1) gate-error metrics are indeed affected by the many assumptions of the model, (2) consecutive gate errors do not accumulate linearly, and (3) gate-error metrics are poor predictors for the performance of consecutive gates. Additionally, we discuss a potential limitation in the scalability of the studied device architecture.