Transition from Statistical to Hardware-Limited Scaling in Photonic Quantum State Reconstruction

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Main Authors: Baumann, Attila, Kis, Zsolt, Koltai, János, Vattay, Gábor
Format: Preprint
Published: 2026
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author Baumann, Attila
Kis, Zsolt
Koltai, János
Vattay, Gábor
author_facet Baumann, Attila
Kis, Zsolt
Koltai, János
Vattay, Gábor
contents The theoretical efficiency of classical shadow tomography is predicated on a perfect Haar-random unitary ensemble, yet this mathematical ideal remains physically unattainable in near-term hardware. Here, we report the experimental discovery of a fundamental accuracy bound on integrated photonic processors: a ``Hardware Horizon'' where the reconstruction error undergoes a sharp phase transition. While the error initially obeys the predicted statistical scaling $\mathcal{O}(M^{-1/2})$, it abruptly saturates at a floor determined by the spectral distortions of the realized unitary group. By deriving a phenomenological error model, we decouple the competing mechanisms of static coherent spectral distortion and dynamic decoherence, demonstrating that this intrinsic noise floor imposes a hard bound that statistical accumulation cannot overcome. These findings establish that the utility of shadow tomography on NISQ (noisy intermediate-scale quantum) hardware is defined by a specific scaling law involving hardware parameters, necessitating active compensation strategies to bridge the gap between theoretical purity and the noisy reality of integrated photonics.
format Preprint
id arxiv_https___arxiv_org_abs_2603_12235
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Transition from Statistical to Hardware-Limited Scaling in Photonic Quantum State Reconstruction
Baumann, Attila
Kis, Zsolt
Koltai, János
Vattay, Gábor
Quantum Physics
Disordered Systems and Neural Networks
Emerging Technologies
Optics
The theoretical efficiency of classical shadow tomography is predicated on a perfect Haar-random unitary ensemble, yet this mathematical ideal remains physically unattainable in near-term hardware. Here, we report the experimental discovery of a fundamental accuracy bound on integrated photonic processors: a ``Hardware Horizon'' where the reconstruction error undergoes a sharp phase transition. While the error initially obeys the predicted statistical scaling $\mathcal{O}(M^{-1/2})$, it abruptly saturates at a floor determined by the spectral distortions of the realized unitary group. By deriving a phenomenological error model, we decouple the competing mechanisms of static coherent spectral distortion and dynamic decoherence, demonstrating that this intrinsic noise floor imposes a hard bound that statistical accumulation cannot overcome. These findings establish that the utility of shadow tomography on NISQ (noisy intermediate-scale quantum) hardware is defined by a specific scaling law involving hardware parameters, necessitating active compensation strategies to bridge the gap between theoretical purity and the noisy reality of integrated photonics.
title Transition from Statistical to Hardware-Limited Scaling in Photonic Quantum State Reconstruction
topic Quantum Physics
Disordered Systems and Neural Networks
Emerging Technologies
Optics
url https://arxiv.org/abs/2603.12235