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Demonstration of hardware efficient photonic variational quantum algorithm

Iris Agresti1,*, Koushik Paul2,3,*, Peter Schiansky1,4,9,*, Simon Steiner1,4, Zhenghao Yin1,4, Ciro Pentangelo5, Simone Piacentini5, Andrea Crespi5,6, Yue Ban7 et al.

Francesco Ceccarelli5, Roberto Osellame5, Xi Chen7,†, and Philip Walther1,8,9,‡

  • *These authors contributed equally to this work.
  • †Contact author: xi.chen@csic.es
  • ‡Contact author: philip.walther@univie.ac.at
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Phys. Rev. Research 7, 043021 – Published 8 October, 2025

DOI: https://doi.org/10.1103/d7bb-ybfh

Abstract

Quantum computing has changed the paradigm of computer science, where quantum technologies have promised to outperform classical ones. Such an advantage was only demonstrated for tasks with no application or out of reach for the state-of-the-art quantum technologies. In this context, a promising strategy to find practical use of quantum computers exploits hybrid models, where a quantum device estimates a hard-to-compute quantity, while a classical optimizer trains the parameters. In this work, we demonstrate that single photons and linear optical networks are sufficient for implementing variational quantum algorithms, when the problem specification (ansatz) is tailored to this specific platform. We show this by a proof-of-principle demonstration to tackle an instance of a factorization task, whose solution is encoded in the ground state of a suitable Hamiltonian. This work, which combines Variational Quantum Algorithms with hardware efficient ansätze for linear optics, showcases a promising pathway toward practical applications for photonic quantum platforms.

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Phys. Rev. Research 7, 043021– Published 8 October, 2025
  • Received 7 October 2024
  • Accepted 29 August 2025
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