Automated discovery of heralded ballistic graph state generators for fusion-based photonic quantum computation

[2508.16505] Automated discovery of heralded ballistic graph state generators for fusion-based photonic quantum computation Skip to main content Search Submit Donate Log in Search arXiv Press Enter to search · Advanced search Quantum Physics arXiv:2508.16505 (quant-ph) [Submitted on 22 Aug 2025 ( v1 ), last revised 10 Apr 2026 (this version, v2)] Title: Automated discovery of heralded ballistic graph state generators for fusion-based photonic quantum computation Authors: Gavin S. Hartnett , Dave Kielpinski , Smarak Maity , Pranav S. Mundada , Yuval Baum , Michael R. Hush View a PDF of the paper titled Automated discovery of heralded ballistic graph state generators for fusion-based photonic quantum computation, by Gavin S. Hartnett and 5 other authors View PDF HTML (experimental) Abstract: Designing photonic circuits that prepare graph states with high fidelity and success probability is a central challenge in linear optical quantum computing. Existing approaches rely on hand-crafted designs or fusion-based assemblies. In the absence of multiplexing/boosting, both post-selected ballistic circuits and sequential fusion exhibit exponentially decreasing single-shot yields - a fundamental limitation that makes optimizing individual resource state generators particularly important, as these serve as building blocks in larger FBQC architectures. We present a general-purpose optimization framework for automated photonic circuit discovery using a novel polynomial-based simulation approach, enabling efficient strong simulation and gradient-based optimization. Our framework employs a two-pass optimization procedure: the first pass identifies a unitary transformation that prepares the desired state with perfect fidelity and maximal success probability, and the second pass implements a novel sparsification algorithm that reduces this solution to a compact photonic circuit with minimal beamsplitter count while preserving performance. This sparsification procedure often reveals underlying mathematical structure, producing highly simplified circuits with rational reflection coefficients. We demonstrate our approach by discovering optimized circuits for $3$-, $4$-, and $5$-qubit graph states across multiple equivalence classes. For 4-qubit states, our circuits achieve success probabilities of $2.053 \times 10^{-3}$ to $7.813 \times 10^{-3}$, outperforming the fusion baseline by up to $4.7 \times$. For 5-qubit states, we achieve $5.926 \times 10^{-5}$ to $1.157 \times 10^{-3}$, demonstrating up to $7.5 \times$ improvement. These results include the first known state preparation circuits for certain 5-qubit graph states. Comments: 24 pages, 10 figures Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2508.16505 [quant-ph] (or arXiv:2508.16505v2 [quant-ph] for this version) https://doi.org/10.48550/arXiv.2508.16505 Focus to learn more arXiv-issued DOI via DataCite Related DOI : https://doi.org/10.1103/c4v4-wz65 Focus to learn more DOI(s) linking to related resources Submission history From: Gavin Hartnett S [ view email ] [v1] Fri, 22 Aug 2025 16:30:10 UTC (1,587 KB) [v2] Fri, 10 Apr 2026 19:12:43 UTC (1,610 KB) Full-text links: Access Paper: View a PDF of the paper titled Automated discovery of heralded ballistic graph state generators for fusion-based photonic quantum computation, by Gavin S. Hartnett and 5 other authors View PDF HTML (experimental) TeX Source view license Current browse context: quant-ph < prev | next > new | recent | 2025-08 References & Citations INSPIRE HEP NASA ADS Google Scholar Semantic Scholar export BibTeX citation Loading... BibTeX formatted citation × loading... 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