# Enhanced violations of Leggett-Garg inequalities in an experimental three-level system

## TL;DR

This paper demonstrates enhanced violations of Leggett-Garg inequalities using a three-level photonic system with three-outcome measurements, revealing stronger quantum temporal correlations than standard tests.

## Contribution

The study implements three-outcome measurements in a three-level system to achieve larger violations of Leggett-Garg inequalities, advancing quantum tests of macroscopic realism.

## Key findings

- Significant excess violations of three- and four-time Leggett-Garg inequalities.
- Violations of the quantum-witness equality up to the maximum for three-outcome measurements.
- Highlighting differences between spatial and temporal quantum correlations.

## Abstract

Leggett-Garg inequalities are tests of macroscopic realism that can be violated by quantum mechanics. In this letter, we realise photonic Leggett-Garg tests on a three-level system and implement measurements that admit three distinct measurement outcomes, rather than the usual two. In this way we obtain violations of three- and four-time Leggett-Garg inequalities that are significantly in excess of those obtainable in standard Leggett-Garg tests. We also report violations the quantum-witness equality up to the maximum permitted for a three-outcome measurement. Our results highlight differences between spatial and temporal correlations in quantum mechanics.