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FM: Fall Meeting

FM 33: Quantum Networks: Concepts & Applications

FM 33.7: Talk

Dienstag, 24. September 2019, 15:45–16:00, 1015

Interaction-free discrimination of quantum channels — •Markus Hasenöhrl and Michael M. Wolf — Technische Universität München, Munich, Germany

Interaction-free measurement, as proposed by Elizur and Vaidman in their famous bomb-tester experiment is a way to employ the counterintuitive laws of quantum mechanics to obtain information about an object, without influencing it in an essential way. For example, finding out if there is an ultra-sensitive bomb in a given black box, without causing the bomb to explode. In my talk, I will show how to reinterpret the bomb-tester experiment as a quantum channel discrimination problem and create a framework that generalizes the notion of interaction-free to arbitrary quantum channels. Furthermore, we explore the implications of this new model. We arrive at two major conclusions: the first one being that we can always find out, whether or not there is an object in a given black box, without influencing the object. This is true, even if we have no prior knowledge which object it might be. The second finding then is that it is impossible to find out, which object is present in the black box, without influencing it. Together these results yield a complete characterization of what is possible and impossible to achieve with interaction-free measurements.