Lattice surgery with Bell measurements: Modular fault-tolerant quantum computation at low entanglement cost

• URL: http://arxiv.org/abs/2510.13541v1
• Date: Wed, 15 Oct 2025 13:38:31 GMT
• Title: Lattice surgery with Bell measurements: Modular fault-tolerant quantum computation at low entanglement cost
• Authors: Trond Hjerpekjøn Haug, Timo Hillmann, Anton Frisk Kockum, Raphaël Van Laer,
• Abstract summary: We introduce a protocol for lattice surgery on surface codes in which all non-local operations are Bell measurements.<n>We evaluate our protocol's performance when two logical qubits on separate modules are prepared in a logical Bell state.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Modular architectures are a promising approach to scaling quantum computers to fault tolerance. Small, low-noise quantum processors connected through relatively noisy quantum links are capable of fault-tolerant operation as long as the noise can be confined to the interface. Finding protocols that implement the quantum links between modules as efficiently as possible is essential because inter-module entanglement is challenging to produce at a similar rate and fidelity as local entanglement. We introduce a protocol for lattice surgery on surface codes in which all non-local operations are Bell measurements. The protocol simultaneously confines the link noise and requires only half as many module-crossing gates as previously proposed protocols. To mitigate distance-reducing hook errors, we introduce a strategy of alternating the gate sequence between rounds of syndrome measurement, which prevents multiple hooks from simultaneously aligning with a logical operator in the code. We evaluate our protocol's performance when two logical qubits on separate modules are prepared in a logical Bell state. Circuit-level simulations under depolarizing noise show that the logical error suppression for a given entanglement rate between modules is consistently stronger compared to the best-performing alternative protocols for a wide range of link noise, with a typical 40% entanglement resource saving for a constant logical error rate. Our approach to protocol design is applicable to any quantum circuit that must be divided across processor modules and can therefore guide development of resource-efficient modular quantum computation beyond the surface code.

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