Quantum anti-Zeno effect without wave function reduction

We study the measurement-induced enhancement of the spontaneous decay for a two-level subsystem, wheremeasurements are treated as couplings between the excited state and an auxiliary state rather than the vonNeumann’s wave function reduction. The photon radiated in a fast decay of the atom, from the auxiliary state to the excited state, triggers a quasi-measurement, as opposed to a projectionmeasurement. Our use of the term ‘‘quasi-measurement’’ refers to a ‘‘coupling-based measurement’’. Such frequent quasi-measurements result in an exponential decay of the survival probability of atomic initial state with a photon emission following each quasi-measurement. Our calculations show that the effective decay rate is of the same form as the one based on projection measurements. The survival probability of the atomic initial state obtained by tracing over all the photon states is equivalent to that of the atomic initial state with a photon emission following each quasi-measurement.