Optimal interferometric certification of multi-photon indistinguishability
Abstract
Multiphoton indistinguishability is a key resource for photonic quantum technologies, yet its characterization typically relies on resource-intensive methods. In this work, we develop two efficient and experimentally friendly protocols to estimate or bound the fidelity Find of an N-photon state to the closest perfectly indistinguishable state. The first protocol applies to sources preparing separable states, uses a single Fourier interferometer together with photon-number-resolving detection, and yields tight two-sided bounds on Find. The second protocol combines randomized implementations of linear-optical interferometers with photon counting, enabling direct estimation of Find for arbitrary N-photon states. Both protocols can certify Find = 1 − 𝒪(ε) using provably optimal 𝒪(1/ε) samples, in contrast to previous approaches which required prior assumptions on the model of partial distinguishability. Our methods, based on a multiphoton generalization of the Hong-Ou-Mandel test, bring the rigorous and operationally meaningful certification of multiphoton indistinguishability within reach of current photonic technologies.
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BibTeX
@misc{robbio2026optimal,
title = {{Optimal interferometric certification of multi-photon indistinguishability}},
author = {Marco Robbio and Michał Oszmaniec and Nicolas J. Cerf and Ernesto Galvão and Leonardo Novo},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.37620},
eprint = {2609.37620},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.37620},
}
RIS
TY - UNPB
TI - Optimal interferometric certification of multi-photon indistinguishability
AU - Marco Robbio
AU - Michał Oszmaniec
AU - Nicolas J. Cerf
AU - Ernesto Galvão
AU - Leonardo Novo
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2609.37620
UR - https://arxiv.org/abs/2609.37620
AB - Multiphoton indistinguishability is a key resource for photonic quantum technologies, yet its characterization typically relies on resource-intensive methods. In this work, we develop two efficient and experimentally friendly protocols to estimate or bound the fidelity F_ind of an N-photon state to the closest perfectly indistinguishable state. The first protocol applies to sources preparing separable states, uses a single Fourier interferometer together with photon-number-resolving detection, and yields tight two-sided bounds on F_ind. The second protocol combines randomized implementations of linear-optical interferometers with photon counting, enabling direct estimation of F_ind for arbitrary N-photon states. Both protocols can certify F_ind = 1 − 𝒪(ε) using provably optimal 𝒪(1/ε) samples, in contrast to previous approaches which required prior assumptions on the model of partial distinguishability. Our methods, based on a multiphoton generalization of the Hong-Ou-Mandel test, bring the rigorous and operationally meaningful certification of multiphoton indistinguishability within reach of current photonic technologies.
ER -