Reducing the Error Rate of a Superconducting Logical Qubit using Analog Readout Information

Conference Paper (2024)
Author(s)

H.A.S. Ali (TU Delft - QCD/DiCarlo Lab, Kavli institute of nanoscience Delft)

Jorge Marques (Kavli institute of nanoscience Delft)

Ophelia Crawford (Riverlane)

Joonas Majaniemi (Riverlane)

Marc Serra-Peraltal

David Byfield (Riverlane)

Boris Mihailov Varbanov (TU Delft - QCD/Terhal Group)

Barbara M. Terhal (TU Delft - Discrete Mathematics and Optimization)

Leonardo di Carlo (Kavli institute of nanoscience Delft, TU Delft - QN/DiCarlo Lab, TU Delft - QCD/DiCarlo Lab)

Earl Campbell (Riverlane, University of Sheffield)

Research Group
Discrete Mathematics and Optimization
DOI related publication
https://doi.org/10.1109/QCE60285.2024.10316
More Info
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Publication Year
2024
Language
English
Research Group
Discrete Mathematics and Optimization
Bibliographical Note
Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.@en
Pages (from-to)
382-383
ISBN (electronic)
9798331541378
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Abstract

Quantum error correction allows for quantum information to be preserved using logical qubits, which are subject to lower error rates than their constituent physical qubits. The degree of error suppression depends on the choice of error correcting code and distance, the underlying physical error rate, and the accuracy of the decoder. While traditional decoders utilise a binary (hard) syndrome, recent work shows that additional (soft) information captured during qubit readout can be effectively utilised to improve decoding accuracy. In this work, we present experimental results from a distance-three surface code implemented on transmon qubits, where we perform Z-stabiliser measurements to protect the state of the logical qubit against bit-flip errors. We initialise the logical qubit in one of 16 possible computational states representing the logical zero state, and perform repeated stabiliser checks over a variable number of rounds to preserve the state over time. We compare the decoding performance for a hard minimum-weight perfect matching decoder against a soft variant where rich measurement information is incorporated, and demonstrate an improved logical fidelity. Additionally, we employ a recurrent neural network decoder with both soft and hard variants and observe improved performance when soft information is used. The general nature of soft information makes it widely applicable to different physical qubit platforms, where it can be leveraged to shorten measurement times and improve the logical fidelity in quantum error correction experiments. Pre-print available at arXiv:2403.00706.

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