Experimental demonstration of interaction-free measurements
Paul G. Kwiat, Harald Weinfurter, Anton Zeilinger
Abstract
It is now well-understood that the complementary wave- and particle-like natures of quanta enable one to make measurements that are “interaction-free” -- one can determine the presence or absence of an object, even a completely absorbing object, without any photons being absorbed. The first proposal of such a scheme was limited to an efficiency of 50% -- at most half of the measurements could be interaction free [1]. By using an application of the Quantum Zeno effect, one can in fact have the fraction of interaction-free measurements arbitrarily close to one [2].