Superselection rules, quantum measurement, and the Schrödinger's cat

Abstract

A precise formulation of superselection rules in quantum mechanics is presented. An explicit measurement model is then constructed using the idea of superselection rules so formulated. The model is free from the usual difficulties associated with the projection postulate and it also allows a measurement to be completed within finite time interval.

Ensemble interpretations of quantum mechanics. A modern perspective

“…An interesting approach to quantum measurement has been developed by Wan [243] (and later extended by Bub [244]). This is based on the use of superselection rules.…”

Superselection Rules for Philosophers

“…We shall then say that the system possesses superselection rules'' (p. 29). 23 For examples where ''superselection rule'' is taken to mean what is called here a very strong rule, see Bogolubov et al (1975) and Wan (1980). Indeed, most texts simply assume that superselection rules are of the very strong variety.…”

“…Thus, an advocate of the superselection account of measurement must exploit the loophole mentioned above that H 6 2 O: This is done explicitly by Wan (1980). The general sentiment in the philosophical community is that the price is too high (see Hughes 1989, Sec.…”

Structure of the Algebra of Effective Observables in Quantum Mechanics

“…Therefore, P kn | B(EknH) is the conditional expectation onto CE kn and formula (9) follows. K Thus, if r(1)=1 we obtain the Wan scheme [4], while for any r(k)>1 the minimal projectors in a corresponding coherent subspace are of dimension r(k), and so we get the case of generalized rays. The restriction of the gauge group to subspace E kn H is isomorphic to the unitary group U(r(k)).…”