Experimental and theoretical progress in interaction-free measurements

Using a hybrid of a simple interference technique and an application of the quantum Zeno effect, it is possible to optically determine the presence of an absorbing object with an arbitrarily low probability that a photon is actually absorbed. We have demonstrated the feasibility of systems in which up to 85% of the measurements could be "interaction-free". Also, we have started investigating the possibility of using these techniques to allow "interaction-free" imaging of objects; our prototype schemes have shown resolutions of less than 10 mu m. Finally, we present a curious phenomenon that occurs when the object in question is only partially transmitting, which should allow a seeming violation of Beer's law.