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On-Chip Semi-Device-Independent Quantum Random Number Generator Exploiting Contextuality

Maddalena Genzini1, Caterina Vigliar1, Mujtaba Zahidy1, Hamid Tebyanian2, Andrzej Gajda3, Klaus Petermann4, Lars Zimmermann3,5, Davide Bacco6,7, and Francesco Da Ros1

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PRX Quantum 7, 033022 – Published 4 August, 2026

DOI: https://doi.org/10.1103/62lv-gmsz

Abstract

We present a semi-device-independent quantum random number generator (QRNG) based on the violation of a contextuality inequality, implemented by the integration of two silicon photonic chips. Our system combines a heralded single-photon source with a reconfigurable interferometric mesh to implement qutrit state preparation, transformations, and measurements suitable for testing a KCBS contextuality inequality. This architecture enables the generation of random numbers from the intrinsic randomness of single-photon interference in a complex optical network, while simultaneously allowing a quantitative certification of their security without requiring entanglement. We observe a contextuality violation exceeding the classical bound by more than 10σ, unambiguously confirming non-classical behavior. From this violation, we certify a conditional min-entropy per experimental round of Hmin=0.077±0.002, derived via a tailored semidefinite-programming-based security analysis. Each measurement outcome therefore contains at least 0.077±0.002  bits of extractable genuine randomness, corresponding to an asymptotic generation rate of 21.7±0.5  bits/s. These results establish a viable route toward semi-device-independent quantum random number generators compatible with practical integrated photonic quantum networks.

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Popular Summary

True randomness is the cornerstone of security, yet certifying it without trusting every hardware component remains a challenge. We report an on-chip quantum random number generator that exploits quantum contextuality, i.e., the quantum property in which measurement outcomes depend on their experimental context. By manipulating photonic qutrits on a silicon chip, we observed a 10-standard-deviation violation of the KCBS inequality and provided a rigorous mathematical certification of randomness. This work successfully combines foundational quantum tests with scalable silicon photonics, offering a path toward integrating semi-device quantum random generators into future quantum photonic networks.

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PRX Quantum 7, 033022– Published 4 August, 2026
  • Received 17 December 2025
  • Revised 17 April 2026
  • Accepted 12 June 2026
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