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Quantum Snakes on a Plane: Mobile, Low-Dimensional Logical Qubits on a 2D Surface

Adam Siegel1,2,*, Zhenyu Cai1,2, Hamza Jnane1,2, Balint Koczor1,3, Shaun Pexton1, Armands Strikis1,4, and Simon Benjamin1,2

  • *Contact author: adam@quantummotion.tech
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PRX Quantum 7, 010339 – Published 25 February, 2026

DOI: https://doi.org/10.1103/494s-jd8h

Abstract

Recent demonstrations indicate that silicon-spin quantum processing unit will be able to shuttle physical qubits rapidly and with high fidelity—a desirable feature for maximizing logical connectivity, supporting new codes, and routing around damage. However it may seem that shuttling at the logical level is unwise: static defects in the device may “scratch” a logical qubit as it passes, causing correlated errors to which the code is highly vulnerable. Here we explore an architecture where logical qubits are 1D strings (“snakes”) which can be moved freely over a planar latticework. Possible scratch events are inferred via monitor qubits and the complementary gap; if deemed a risk, remarkably the shuttle process can be undone in a way that negates any corruption. This leads to high levels of tolerance against shuttling-related imperfections and enables logical operations between snakes by a semitransversal method. We conclude that this approach is suitable for fault-tolerant computing in both near-term and long-term, mature-era silicon devices.

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Popular Summary

Recent experiments suggest that silicon-based quantum processors will be able to move (or “shuttle”) qubits rapidly and with very high fidelity. This mobility could greatly enhance how qubits are connected, allow new types of error-correcting codes, and even let quantum circuits route around damaged regions of a chip. In this work, we capitalize on this asset to propose a fault-tolerant fully scalable architecture with all-to-all logical-level connectivity. Logical qubits take the form of one-dimensional strings of physical qubits, which we call snakes, that can move freely across a two-dimensional lattice.

At first glance however, shuttling logical qubits seems risky: fixed defects in the hardware could ”scratch” a logical qubit as it moves, introducing correlated errors that standard error-correction schemes struggle to handle. We however show that logical shuttling can in fact be made safe and useful. Potential damage events during motion are detected indirectly using nearby monitor qubits and decoder confidence. If a move is judged to be dangerous, the shuttling operation can be reversed via a tailored protocol, effectively undoing the motion in a way that cancels any corruption of the logical information. We also show how these mobile logical qubits can interact using a semitransversal gate protocol.

Together, these results demonstrate that mobile logical qubits are not only viable, but may offer a powerful approach to building flexible, defect-tolerant silicon-spin quantum computers.

Article Text

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Outline

Information

PRX Quantum 7, 010339– Published 25 February, 2026
  • Received 15 February 2025
  • Revised 2 July 2025
  • Accepted 17 December 2025
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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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