Are you certain, Mr. Heisenberg?

Heisenberg's Uncertainty principle is arguably one of the most famous foundations of quantum physics. It says that not all properties of a quantum particle can be measured with unlimited accuracy. Until now, this has often been justified by the notion that every measurement necessarily has to disturb the quantum particle, which distorts the results of any further measurements. This, however, turns out to be an oversimplification. In neutron experiments carried out by professor Yuji Hasegawa and his team at Vienna University of Technology, different sources of quantum uncertainty can now be distinguished, validating theoretical results by collaborators from Japan. The influence of the measurement on the quantum system is not always the reason for uncertainty. Heisenberg's arguments for the uncertainty principle have to be revisited - the uncertainty principle itself however remains valid.