Neutron interferometry and the joint measurement of incompatible observables

Abstract

Different neutron-interferometric setups for the joint detection of ``path'' and ``interference'' are investigated from the point of view of the theory of joint measurement. It is seen that this joint detection can only be done with limited quality. This substantiates Bohr's insistence that the impossibility of jointly seeing interference and path is a consequence of the uncertainty principle. A connection between joint measurement and Wigner distributions is noted.