Insolubility from No-Signalling

This paper improves on the result in my (Bacciagaluppi in Eur. J. Philos. Sci. 3: 87–100, 2013), showing that within the framework of the unitary Schrödinger equation it is impossible to reproduce the phenomenological description of quantum mechanical measurements (in particular the collapse of the state of the measured system) by assuming a suitable mixed initial state of the apparatus. The result follows directly from the no-signalling theorem...