Boson sampling beyond the dilute regime: second moments and anti-concentration

Fuente: arXiv
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Main Authors: Mhiri, Hela, Thomas, Hugo, Monbroussou, Léo, Chabaud, Ulysse, Holmes, Zoë, Kashefi, Elham
Format: Preprint
Published: 2026
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author Mhiri, Hela
Thomas, Hugo
Monbroussou, Léo
Chabaud, Ulysse
Holmes, Zoë
Kashefi, Elham
author_facet Mhiri, Hela
Thomas, Hugo
Monbroussou, Léo
Chabaud, Ulysse
Holmes, Zoë
Kashefi, Elham
contents Boson sampling is a leading candidate for demonstrating quantum advantage in photonic systems. Despite significant experimental and theoretical progress, a characterization of its output statistics remains incomplete. This is especially true beyond the dilute regime, where photon collisions and bunching become significant. The associated saturated regime, characterized by mode number growing linearly with photon number, or more generally sub-quadratically, is precisely the regime of greatest experimental interest. As a consequence, anti-concentration of the output distribution--a key ingredient in hardness arguments--remains poorly understood in boson sampling. In this work, we leverage representation-theoretic tools to address this gap, obtaining closed-form expressions for second moments of generic particle-number-preserving bosonic observables. We express these quantities in terms of Hilbert-Schmidt norms of projections onto irreducible components of the operator space and show that these projection norms admit compact analytical expressions by exploiting the underlying symmetry structure. Focusing on Fock state output probabilities, we further establish anti-concentration beyond the dilute regime. Together with recent complexity-theoretic results, our findings strengthen hardness guarantees for boson sampling in experimentally interesting settings.
format Preprint
id arxiv_https___arxiv_org_abs_2604_14323
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Boson sampling beyond the dilute regime: second moments and anti-concentration
Mhiri, Hela
Thomas, Hugo
Monbroussou, Léo
Chabaud, Ulysse
Holmes, Zoë
Kashefi, Elham
Quantum Physics
Boson sampling is a leading candidate for demonstrating quantum advantage in photonic systems. Despite significant experimental and theoretical progress, a characterization of its output statistics remains incomplete. This is especially true beyond the dilute regime, where photon collisions and bunching become significant. The associated saturated regime, characterized by mode number growing linearly with photon number, or more generally sub-quadratically, is precisely the regime of greatest experimental interest. As a consequence, anti-concentration of the output distribution--a key ingredient in hardness arguments--remains poorly understood in boson sampling. In this work, we leverage representation-theoretic tools to address this gap, obtaining closed-form expressions for second moments of generic particle-number-preserving bosonic observables. We express these quantities in terms of Hilbert-Schmidt norms of projections onto irreducible components of the operator space and show that these projection norms admit compact analytical expressions by exploiting the underlying symmetry structure. Focusing on Fock state output probabilities, we further establish anti-concentration beyond the dilute regime. Together with recent complexity-theoretic results, our findings strengthen hardness guarantees for boson sampling in experimentally interesting settings.
title Boson sampling beyond the dilute regime: second moments and anti-concentration
topic Quantum Physics
url https://arxiv.org/abs/2604.14323