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arXiv · 2610.05152

The diffusive spectral gap of the qubit eSWAP chain

Yanying Liang·Haoran Zhu
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Abstract

We prove that the second-moment Hamiltonian of the open qubit eSWAP chain has a diffusive spectral gap, resolving a conjecture of Li, Zheng, Liu, Jiang, and Liu. We also characterise the ground space on every connected interaction graph with at least five vertices and prove a uniform lower bound for the unnormalised complete-graph gap. We apply these results to sequential and brickwork circuits and prove that the periodic chain also has a diffusive spectral gap.

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Yanying Liang, Haoran Zhu. 2026-10-04. The diffusive spectral gap of the qubit eSWAP chain. https://arxiv.org/abs/2610.05152

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