https://doi.org/10.1140/epjd/e2011-10714-3
'Measurement of quantum mechanical operators' revisited
University of York, Department of Mathematics, Mathematical Physics Section,
YO10 5, DD York, UK
a e-mail: paul.busch@york.ac.uk
Received:
20
December
2010
Published online:
25
March
2011
The Wigner-Araki-Yanase (WAY) theorem states a remarkable limitation to quantum mechanical measurements in the presence of additive conserved quantities. Discovered by Wigner in 1952, this limitation is known to induce constraints on the control of individual quantum systems in the context of information processing. It is therefore important to understand the precise conditions and scope of the WAY theorem. Here we elucidate its crucial assumptions, briefly review some generalizations, and show how a particular extension can be obtained by a simple modification of the original proofs. We also describe the evolution of the WAY theorem from a strict no-go verdict for certain, highly idealized, precise measurements into a quantitative constraint on the accuracy and approximate repeatability of imprecise measurements.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2011
