Quantum computing is scalable on a planar array of qubits with fabrication defects

TL;DR

This paper demonstrates that large-scale quantum computing is feasible on a planar array of qubits even with fabrication defects, using a robust surface code protocol to maintain fault tolerance.

Contribution

It introduces a threshold theorem for scalable quantum computing on defective 2D qubit arrays, employing a new stabilizer measurement protocol within a surface code architecture.

Findings

Quantum computation can be reliably performed despite fabrication defects.

A robust stabilizer measurement protocol compensates for inactive qubits.

Scalability is achievable with current experimental approaches.

Abstract

To successfully execute large-scale algorithms, a quantum computer will need to perform its elementary operations near perfectly. This is a fundamental challenge since all physical qubits suffer a considerable level of noise. Moreover, real systems are likely to have a finite yield, i.e. some non-zero proportion of the components in a complex device may be irredeemably broken at the fabrication stage. We present a threshold theorem showing that an arbitrarily large quantum computation can be completed with a vanishing probability of failure using a two-dimensional array of noisy qubits with a finite density of fabrication defects. To complete our proof we introduce a robust protocol to measure high-weight stabilizers to compensate for large regions of inactive qubits. We obtain our result using a surface code architecture. Our approach is therefore readily compatible with ongoing experimental efforts to build a large-scale quantum computer.