Automated Compilation Including Dropouts: Tolerating Defective Components in Stabiliser Codes

TL;DR

This paper introduces ACID, an automated framework for generating syndrome extraction circuits for stabiliser codes that tolerates fabrication defects, significantly improving yield and reducing circuit depth overhead in quantum devices.

Contribution

ACID provides a novel optimization-based method for syndrome extraction in the presence of defects, applicable to multiple quantum error-correcting codes, with improved efficiency over prior algorithms.

Findings

ACID achieves circuit depth of 1 to 1.5 times the defect-free circuits.

ACID increases the yield of surface code chips with low logical error rates by up to 3 times.

Demonstrates applicability to surface, bicycle, and colour codes with manageable overhead.

Abstract

Utility-scale solid-state quantum devices will need to fabricate quantum devices at scale using imperfect processes. By introducing tolerance to fabrication defects into the design of the quantum devices, we can improve the yield of usable quantum chips and lower the cost of useful systems. Automated Compilation Including Dropouts (ACID) is a framework that works in the ancilla-free (or `middle-out') paradigm, to generate syndrome extraction circuits for general stabiliser codes in the presence of defective couplers or qubits. In the ancilla-free paradigm, we do not designate particular qubits as measurement ancillas, instead measuring stabilisers using any of the data qubits in their support. This approach leads to a great deal of flexibility in how syndrome extraction circuits can be implemented. ACID works by constructing and solving an optimisation problem within the ancilla-free paradigm to find a short syndrome extraction circuit. Applied to the surface code, ACID produces syndrome-extraction circuits of depth between $1\times$ (no overhead) and $1.5\times$ relative to the depth of defect-free circuits. The LUCI algorithm, the best prior art, yielded a $2 \times$ overhead, so ACID offers a significant time saving. The yield of surface code chips with a logical error rate at most $10\times$ the dropout-free baseline is up to $3\times$ higher using ACID than using LUCI. I demonstrate the broad applicability of ACID by compiling syndrome extraction circuits for bivariate bicycle codes and the colour code. For these circuits, we incur a circuit-depth overhead of between $1\times$ (no overhead) and $2.5\times$ relative to defect-free circuits. I believe this work is the first to simulate both of these families of codes in the presence of fabrication defects.