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arXiv · 2609.37628

Operational theory for photonic circuits: generalizing linear optics beyond quantum theory

Ismaël Septembre·Matthias Kleinmann·Martin Plávala
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Abstract

We use the analogy between the quadrature operators in quantum optics and the phase-space coordinates in a mechanical harmonic oscillator to generalise the theory of linear optics beyond quantum theory. For this, we introduce a framework for analysing photonic circuits within generalised probabilistic theories based on quadrature operators. Using this framework, we ask whether phenomena like the Hong-Ou-Mandel effect, Mach-Zehnder interferometry are specific to quantum theory or also occur across a broader class of theories. We find the latter: the vanishing photon coincidences at the output of a beam splitter also occur for classical light and for a modified version of quantised light. Similarly, for Mach-Zehnder interferometry we find that there is no qualitative difference between quantum theory and these alternative theories. Our framework can serve as a foundation to study generalised theories of complex photonic set-ups and photonic quantum computers.

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Ismaël Septembre, Matthias Kleinmann, Martin Plávala. 2026-09-29. Operational theory for photonic circuits: generalizing linear optics beyond quantum theory. https://arxiv.org/abs/2609.37628

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