Scalable quantum error correction tailored for a heavy-hex qubit array

TL;DR

This paper introduces the dynamic compass code, a scalable quantum error correction method optimized for heavy-hex qubit arrays, demonstrating significant logical error rate improvements through noise-informed decoding strategies.

Contribution

The paper presents the dynamic compass code tailored for heavy-hex qubit arrays and demonstrates its effectiveness with noise-aware decoding in a superconducting qubit experiment.

Findings

Achieved up to 38.3% reduction in logical error rate.

Implemented a distance-5 dynamic compass code on superconducting qubits.

Showed that detailed noise characterization improves decoder performance.

Abstract

To produce an operable quantum computer that is made with imperfect hardware, we must design and test scalable quantum error correcting codes that are suited for the devices we can build and, in unison, develop decoding strategies that accommodate device-specific noise characteristics. Here, we introduce the \emph{dynamic compass code}, a subsystem code with a novel syndrome extraction cycle, that has a competitive threshold while making efficient use of qubits arranged on a heavy-hex lattice. We use a superconducting qubit array to implement a distance-5 instance of this code, and demonstrate how detailed noise characterisation can boost decoder performance to yield significant improvements in logical error rates. We perform averaged circuit eigenvalue sampling (ACES) to acquire detailed context-dependent error information on all elements of the syndrome extraction process. Furthermore, we leverage soft information produced from measurement devices to augment the decoder with measurement error information and detect leakage errors for exclusion through post-selection. Our noise-informed approach yields up to 38.3\% improvement in the logical error rate of a distance-5 implementation of the dynamic compass code in experiment.