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  • Open Access

Parallel Logical Measurements via Quantum Code Surgery

Alexander Cowtan1,*, Zhiyang He2, Dominic J. Williamson3, and Theodore J. Yoder4

  • *Contact author: akcowtan@gmail.com
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PRX Quantum 7, 020325 – Published 8 May, 2026

DOI: https://doi.org/10.1103/gj8x-n5gg

Abstract

Quantum code surgery is a flexible and low-overhead technique for performing logical measurements on quantum error-correcting codes, which generalizes lattice surgery. In this work, we present a code surgery scheme, applicable to any qubit stabilizer low-density parity check (LDPC) code, that fault-tolerantly measures many logical Pauli operators in parallel. For a collection of logically disjoint Pauli product measurements supported on t logical qubits, our scheme uses O(tω(logt+log3ω)) ancilla qubits, where ω≥d is the maximum weight of the single logical Pauli representatives involved in the measurements and d is the code distance. This is all done in time O(d) independent of t. Our proposed scheme preserves both the LDPC property and the fault-distance of the original code, without requiring ancillary logical codeblocks, which may be costly to prepare. This addresses a shortcoming of several recently introduced surgery schemes, which can only be applied to measure a limited number of logical operators in parallel if they overlap on data qubits.

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Popular Summary

To build large, fault-tolerant quantum computers capable of outperforming classical supercomputers, quantum error-correction is required to protect the quantum memory during computation. An important operation in quantum computing is measurement, which can be used to perform quantum computation and also allows the user to retrieve classical output.

Low-density parity check (LDPC) codes are a type of error-corrected quantum memory, which have the potential to store data more efficiently than previous quantum error-correction codes. In this work, we introduce a scheme for performing many parallel measurements on any quantum LDPC code. Our scheme is efficient and preserves the error-correction properties throughout. This is accomplished by combining several LDPC code surgery techniques, and constitutes a step toward computing efficiently on large quantum error-correction codes with low overhead.

Article Text

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PRX Quantum 7, 020325– Published 8 May, 2026
  • Received 9 August 2025
  • Revised 21 January 2026
  • Accepted 7 April 2026
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