Experimental Detection of Quantum Coherent Evolution through the Violation of Leggett-Garg-Type Inequalities

We discuss the use of inequalities of the Leggett-Garg type (LGtI) to witness quantum coherence and present the first experimental violation of this type of inequalities using a light-matter interfaced system. By separately benchmarking the Markovian character of the evolution and the translational invariance of the conditional probabilities, the observed violation of a LGtI is attributed to the quantum coherent character of the process. These results provide a general method to benchmark quantumness when the absence of memory effects can be independently certified and confirm the persistence of quantum coherent features within systems of increasing complexity.