Work

Transition from statistical to hardware-limited scaling in photonic quantum state reconstruction

Year: 2026

Type: article

Abstract: 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 characterization of a hardware-induced systematic error floor on integrated photonic processors: an operational Hardware Horizon, where the reconstruction error undergoes a sharp crossover. While the error initially obeys the predicted statistical scaling O ( M − 1 / 2 ) in a variance-dominated regime, it abruptly saturates at a floor determined by the spectral distortions of the realized unitary group, marking a transition to a bias-dominated regime. By deriving a phenomenological error model, we decouple the competing mechanisms of static coherent spectral distortion and dynamic decoherence, demonstrating that this device-specific noise floor imposes a systematic saturation limit 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.

Source: Physical Review A

DOI: 10.1103/3gsc-krrq

Authors: Attila Baumann, Zsolt Kis, János Koltai, Gábor Vattay

Institutions: Eötvös Loránd University, Hungarian Research Network

Language: English

Topic: Quantum Computing Algorithms and Architecture

Subfield: Artificial Intelligence

Field: Computer Science

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $2,675

Funder: Nemzeti Kutatási Fejlesztési és Innovációs Hivatal