Multiple-measurement Leggett-Garg inequalities

In the investigation of the quantum to classical transition, the Leggett-Garg inequality represents what Bell's inequality is for the study of entanglement and nonlocality: a definite quantitative test showing the inadequacy of familiar lines of thought in interpreting quantum phenomena. Here we discuss the generalization of the Leggett-Garg inequality to an arbitrary number of measurements in the perspective of its use as a tool for characterizing nondestructive measurement devices.