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. 
Zong-Quan Zhou, Susana F. Huelga, Chuan-Feng Li, and Guang-Can Guo
quant-ph