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Entanglement Boosting: Low-Volume Logical Bell Pair Preparation for Distributed Fault-Tolerant Quantum Computation

Shinichi Sunami1,2,*,†, Yutaka Hirano1,*, Toshihide Hinokuma1, and Hayata Yamasaki1,3,‡

  • *These authors contributed equally to this work.
  • †Contact author: shinichi.sunami@nano-qt.com
  • ‡Contact author: hayata.yamasaki@nano-qt.com
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PRX Quantum 7, 033014 – Published 14 July, 2026

DOI: https://doi.org/10.1103/tz8f-6xwk

Abstract

Distributed architecture is a promising route to scaling fault-tolerant quantum computing (FTQC) beyond the inherent limitations of single processors, for which high-fidelity logical Bell pairs need to be prepared from many noisy physical Bell pairs with high efficiency. For practical implementation of distributed FTQC, logical Bell pair preparation must be designed not only for efficient Bell pair consumption but also for the spacetime volume of the protocol; however, entanglement distillation protocols have primarily focused on minimizing the consumption of Bell pairs, often resulting in protocols that require a substantial number of local operations. A key challenge is to find an appropriate balance between these two contrasting features. To resolve this issue, we introduce a metric for characterizing the practical cost of preparing high-fidelity logical Bell pairs, link-limited volume (LLV), which is a circuit-volume metric incorporating, in a single quantity, both the cost of physical Bell pair consumption and the volume associated with local operations. Guided by this metric, we propose the entanglement boosting protocol that achieves efficient preparation of logical Bell pairs encoded in rotated surface code, with LLV reduced by orders of magnitude compared to prior state-of-the-art methods. In this protocol, paralleling recent advances in magic state cultivation, we employ soft-information decoders and postselection to suppress the logical error rates of Bell pairs to practical levels, e.g. less than 10−10 from 86 noisy physical Bell pairs at 1% error, while all local operations are implementable within a spatial region of a single surface-code patch with two-dimensional local connectivity. This is a substantial reduction from other protocols, such as remote lattice surgery operations requiring nearly 1000 physical Bell pairs under the same setting. To further augment the entanglement boosting, we also present a pipelined implementation of entanglement distillation using high-rate quantum error-correcting codes, enabling arbitrarily low logical error rates while also maintaining physically efficient implementations. These results pave the way for the practical implementation of distributed FTQC, reinforcing the benefits of fast interconnect technologies and serving as a guiding principle for the efficient design of protocols and devices.

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Physics Subject Headings (PhySH)

Popular Summary

Useful, large-scale fault-tolerant quantum computers will require far more qubits than a single processor can hold, so a leading strategy is to link many smaller processors into one large machine. These links rely on shared entanglement in the form of Bell pairs. The Bell pairs generated over a network are noisy, so they must be turned into high-fidelity, error-corrected logical Bell pairs before they can support reliable computation. Doing this through entanglement distillation usually demands either many network-generated Bell pairs or a large amount of local quantum processing. In this work, we introduce a single cost measure that captures both factors together, and use it to design a new protocol called entanglement boosting. Our method reaches very low logical error rates while consuming only a small number of physical Bell pairs, while confining all local operations to a small spacetime footprint. This makes linking quantum processors substantially more practical, bringing large-scale distributed fault-tolerant quantum computing closer to reality.

Article Text

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PRX Quantum 7, 033014– Published 14 July, 2026
  • Received 10 December 2025
  • Revised 3 May 2026
  • Accepted 4 June 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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