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MON: Monday Contributed Sessions

MON 23: Poster Session: Fundamental Aspects and Model Systems

MON 23.5: Poster

Monday, September 8, 2025, 18:30–20:30, ZHG Foyer 1. OG

Partial distinguishability in the interference of Gaussian states in linear unitary networks — •Matheus Eiji Ohno Bezerra and Valery Shchesnovich — Universidade Federal do ABC, Santo André, State of São Paulo, 09210-170 Brazil

Partial distinguishability of the photons is a fundamental property of the quantum interference and an important source of noise in photonic quantum information protocols, particularly in Boson Sampling schemes. It originates from the imperfect overlap in the internal degrees of freedom of the photons (polarization, spectral profile, arrival time, etc). This effect was first demonstrated in the Hong-Ou-Mandel experiment, where two single photons interfere in a beam splitter and the coincidence events vanish when they are perfectly indistinguishable. Let |ψk⟩ the internal states of the photons, with overlaps given by ⟨ ψi | ψj ⟩ = rij ei θij. When looking to the partial distinguishability, in the two-photon interference, only the modulus rij is important; while in the interference of three and more single photons, the phases θij play an important role. However, these effects of partial distinguishability have not been fully explored in the interference of Gaussian states. In this work, we investigate how the partial distinguishability and these internal phases influence the interference of Gaussian states, specifically coherent and squeezed states, when the photons from each source are partially distinguishable. We find that the coherent states exhibit a classical dependence on the individual phases θij, whereas squeezed states display an additional collective dependence of the phase, reminiscent of the behavior seen in the single-photon interference.

Keywords: Gaussian Boson Sampling; Quantum interference; Gaussian states; Partial distinguishability

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