# Single-photon quantum contextuality on a chip

## TL;DR

This paper demonstrates quantum contextuality in a compact integrated photonic chip by violating a non-contextuality inequality, highlighting potential for portable quantum devices leveraging contextuality.

## Contribution

First demonstration of quantum contextuality on a chip using integrated photonics, enabling scalable and portable quantum information processing.

## Key findings

- Violates a CHSH-like inequality by 14 standard deviations
- Uses a single photon delocalized over four spatial modes
- Paves the way for portable contextuality-based quantum devices

## Abstract

In classical physics, properties of the objects exist independently on the context, i.e. whether and how measurements are performed. Quantum physics showed this assumption to be wrong and that Nature is indeed "contextual". Contextuality has been observed in the simplest physical systems such as single particles, and plays fundamental roles in quantum computation advantage. Here, we demonstrate for the first time quantum contextuality in an integrated photonic chip. The chip implements different combinations of measurements on a single photon delocalized on four distinct spatial modes. We show violations of a CHSH-like non-contextuality inequality by 14 standard deviations. This paves the way to compact and portable devices for contextuality-based quantum-powered protocols.