  The paper describes a solution to the problem of quantum measurement that has
been proposed recently. The literal understanding of the basic rule of quantum
mechanics on identical particles violates the cluster separation principle and
so leads to difficulties. A proposal due to Peres of how such difficulties
could be removed is reformulated and extended. Cluster separability leads to a
locality requirement on observables and to the key notion of separation status.
Separation status of a microsystem is shown to change in preparation and
registration processes. The indispensability of detectors plays an important
role. Changes of separation status are alterations of kinematic description
rather than some parts of dynamical trajectories and so more radical than
'collapse of the wave function'. Textbook quantum mechanics does not provide
any information of how separation status changes run, hence new rules must be
formulated. This enables to satisfy the objectification requirement for
registrations. To show how the ideas work, a simplified model of registration
apparatus is constructed.

Quantum Physics