Direct measurement of Bacon-Shor code stabilizers

TL;DR

This paper demonstrates a method to directly and fault-tolerantly measure stabilizers of Bacon-Shor codes using bare ancillary qubits, improving efficiency and error rates compared to surface codes in small quantum systems.

Contribution

The authors introduce a new circuit construction for direct stabilizer measurement in Bacon-Shor codes, enhancing fault tolerance and efficiency.

Findings

Bacon-Shor code outperforms surface code in small systems

Direct measurement reduces qubit and time requirements

Lower error rates achieved with the new method

Abstract

A Bacon-Shor code is a subsystem quantum error-correcting code on an $L \times L$ lattice where the $2(L-1)$ weight-$2L$ stabilizers are usually inferred from the measurements of $(L-1)^2$ weight-2 gauge operators. Here we show that the stabilizers can be measured directly and fault tolerantly with bare ancillary qubits by constructing circuits that follow the pattern of gauge operators. We then examine the implications of this method for small quantum error-correcting codes by comparing distance 3 versions of the rotated surface code and the Bacon-Shor code with the standard depolarizing model and in the context of a trapped ion quantum computer. We find that for a simple circuit of prepare, error correct and measure the Bacon-Shor code outperforms the surface code by requiring fewer qubits, taking less time, and having a lower error rate.