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arXiv · 2411.04405

On fault tolerant single-shot logical state preparation and robust long-range entanglement

Thiago Bergamaschi·Yunchao Liu
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Abstract

Preparing encoded logical states is the first step in a fault-tolerant quantum computation. Standard approaches based on concatenation or repeated measurement incur a significant time overhead. The Raussendorf-Bravyi-Harrington cluster state offers an alternative: a single-shot preparation of encoded states of the surface code, by means of a constant depth quantum circuit, followed by a single round of measurement and classical feedforward. In this work we generalize this approach and prove that single-shot logical state preparation can be achieved for arbitrary quantum LDPC codes. Our proof relies on a minimum-weight decoder and is based on a generalization of Gottesman's clustering-of-errors argument. As an application, we also prove single-shot preparation of the encoded GHZ state in arbitrary quantum LDPC codes. This shows that adaptive noisy constant depth quantum circuits are capable of generating generic robust long-range entanglement.

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Thiago Bergamaschi, Yunchao Liu. 2024-11-07. On fault tolerant single-shot logical state preparation and robust long-range entanglement. https://doi.org/10.4230/lipics.itcs.2025.16

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