Explicit measurement theory for quantum mechanics - art. no. 042109

Motivated by decoherence theory, a heuristic formulation of quantum measure ment theory is produced in which the macroscopic measuring instrument is ex plicitly included on the same footing as the quantum system being measured. The theory takes the form of a master equation for the joint density matri x of the measuring instrument and quantum system. The master equation refer s to both systems in a symmetric way. Solution of the master equation using quantum trajectory theory furnishes a quasi-Hamiltonian evolution of the m easuring process, punctuated by quantum jumps involving both the atomic sys tem and the states of the measuring instrument. The projection postulate of quantum measurement theory emerges as a result from the formalism. A perva sive quantum Zeno effect and delayed detection are two phenomena. usually m asked by the standard treatment of quantum measurement theory, which appear in this formalism.