Explicit measurement theory for quantum mechanics

Motivated by decoherence theory, a heuristic formulation of quantum measurement theory is produced in which the macroscopic measuring instrument is explicitly included on the same footing as the quantum system being measured. The theory takes the form of a master equation for the joint density matrix of the measuring instrument and quantum system. The master equation refers to both systems in a symmetric way. Solution of the master equation using quantum trajectory theory furnishes a quasi-Hamiltonian evolution of the measuring process, punctuated by quantum jumps involving both the atomic system and the states of the measuring instrument. The projection postulate of quantum measurement theory emerges as a result from the formalism. A pervasive quantum Zeno effect and delayed detection are two phenomena, usually masked by the standard treatment of quantum measurement theory, which appear in this formalism.