Experimental demonstration of an efficient interaction-free measurement in a Fabry-Perot interferometer

Summary form only given.The purpose of an interaction-free measurement is to detect the presence of an object without letting any energy quanta be absorbed by the object. In this work we present interaction-free measurement results using a Fabry-Perot interferometer as a measurement apparatus. If the cavity of the interferometer is empty, an incoming photon will be transmitted through the interferometer. If an absorbent is placed between the mirrors, the photon will be reflected by the first mirror. By detecting which way the photon takes, we will gain information about the presence of the absorbent without losses/interaction. For a perfect measurement, the figure of merit will be equal to the mirror reflectivity R. Thus, in theory, one can approach the perfect interaction-free measurement simply by increasing R.