Fault-tolerant detection of a quantum error

TL;DR

This paper presents a hardware-efficient fault-tolerant error detection scheme for quantum computing that significantly reduces error propagation and increases qubit coherence time using a single transmon ancilla and cavity encoding.

Contribution

It introduces a novel fault-tolerant error detection method that suppresses ancilla error spreading and enhances qubit coherence, leveraging system-specific error models and in situ engineered interactions.

Findings

Suppressed ancilla error spreading by a factor of 5.

Increased logical qubit dephasing time by an order of magnitude.

Demonstrated hardware-efficient fault-tolerant error detection approach.

Abstract

A critical component of any quantum error-correcting scheme is detection of errors by using an ancilla system. However, errors occurring in the ancilla can propagate onto the logical qubit, irreversibly corrupting the encoded information. We demonstrate a fault-tolerant error-detection scheme that suppresses spreading of ancilla errors by a factor of 5, while maintaining the assignment fidelity. The same method is used to prevent propagation of ancilla excitations, increasing the logical qubit dephasing time by an order of magnitude. Our approach is hardware-efficient, as it uses a single multilevel transmon ancilla and a cavity-encoded logical qubit, whose interaction is engineered in situ by using an off-resonant sideband drive. The results demonstrate that hardware-efficient approaches that exploit system-specific error models can yield advances toward fault-tolerant quantum computation.