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arXiv · 2608.15608

Linear optical fan-out gates using fewer ancillary single photons with enhanced success probability

Wen-Qiang Liu·Hai-Rui Wei
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Abstract

Photonic quantum gates are fundamental building blocks for a wide range of optical quantum information processing tasks. We propose an efficient linear-optical scheme for implementing a post-selected three-qubit fan-out gate (also known as a controlled-NOT-NOT gate) using only two ancillary single photons and linear optical elements. The scheme can be generalized to an $n$-qubit fan-out gate, requiring $(n-1)$ ancillary single photons and $(3n-3)$ polarizing beam splitters (PBSs), with a success probability of $\left(\frac{1}{4}\right)^{n-1}$. Compared to the standard gate decomposition approach, which requires $(2n-2)$ ancillary single photons, $(5n-5)$ PBSs, and yields a success probability of $\left(\frac{1}{8}\right)^{n-1}$. Our scheme significantly reduces the resource overhead and improves the success probability. We further evaluate the gate performance and demonstrate improved robustness compared to gate decomposition-based methods.

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Wen-Qiang Liu, Hai-Rui Wei. 2026-08-16. Linear optical fan-out gates using fewer ancillary single photons with enhanced success probability. https://doi.org/10.1103/cs4d-lpfj

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