title: Position measurements obeying momentum conservation.
abstract: We present a hitherto unknown fundamental limitation to a basic measurement: that of the position of a quantum object when the total momentum of the object and apparatus is conserved. This result extends the famous Wigner-Araki-Yanase theorem, and shows that accurate position measurements are only practically feasible if there is a large momentum uncertainty in the apparatus.
authors.affiliation: Mathematical Physics Section, Department of Mathematics, University of York, York, United Kingdom. paul.busch@york.ac.uk
authors.forename: Paul
authors.initials: P
authors.lastname: Busch
authors.forename: Leon
authors.initials: L
authors.lastname: Loveridge