Interaction-free measurements

Following the last speakers example I put on my quantum hat
and take off my many-body hat. In other words, this talk is a bit
different from talks I usually give – less formal and maybe more fun.The
term “interaction-free measurements” poped up the first time in the
80’th by Dicke, but it became more generally known in the early 90’th
after a paper by Elitzur and Vaidman. Seemingly you can measure (affect)
a system without interacting with it. Not surprisingly, the term was
critized by many, but Vaidman seemed to cling on to the idea of the
correctness of the term. I will give my view on it, and also discuss how
it all is related to the work of a former bachelor student of mine.