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arXiv:1912.09410 · Nature Physics

Repeated quantum error detection in a surface code

Christian Kraglund Andersen, Ants Remm, Stefania Lazar, Sebastian Krinner, Nathan Lacroix, Graham J. Norris, Mihai S. Gabureac, Christopher Eichler, Andreas J. Wallraff

Published Jun 8, 2020• 340 citations
arXivHTMLPDF
DOI
10.1038/s41567-020-0920-y

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Whether it is at the fabrication stage or during the course of the quantum computation, e.g. because of high-energy events like cosmic rays, the qubits constituting an error correcting code may be rendered inoperable. Such defects may correspond to individual qubits or to clusters and could potentially disrupt the code sufficiently to generate logical errors. In this paper, we explore a novel a d a p t i v e approach for surface code quantum error correction on a defective lattice. We show that combining an appropriate defect detection algorithm and a quarantine of the identified zone allows one to preserve the advantage of quantum error correction at finite code sizes, at the cost of a qubit overhead that scales with the size of the defect. Our numerics indicate that the code's threshold need not be significantly affected; for example, for a certain scenario where small defects repeatedly arise in each logical qubit, the noise threshold is 2.7 % (versus the defect-free case of 2.9 % ). These results pave the way to the experimental implementation of large-scale quantum computers where defects will be inevitable.