Delayed-choice erasure is investigated in two-photon two-slit experiments that are generalizations of the micromaser experiment of Scully et al. (Nature 351:111–116, 1991). Applying quantum mechanics to the localization detector, it is shown that erasure with delayed choice in the sense of Scully, has an analogous structure as simple erasure. The description goes beyond probabilities. The EPR-type disentanglement, consisting in two mutually incompatible distant measurements, is used as a general framework in both parts of this study. Two simple coherence cases are (...) shown to emerge naturally, and they are precisely the two experiments of Scully et al. The treatment seems to require the relative-reality-of-unitarily-evolving-state (RRUES) approach. Besides insight in the experiments, this study has also the goal of insight in quantum mechanics. The question is if the latter can be more than just a “book-keeping device” for calculating probabilities as Scully et al. modestly and cautiously claim. (shrink)

It was pointed out in the first part of this study (Herbut in Found. Phys. 38:1046–1064, 2008) that EPR-type entanglement is defined by the possibility of performing any of two mutually incompatible distant, i.e., direct-interaction-free, measurements. They go together under the term ‘EPR-type disentanglement’. In this second part, quantum-mechanical insight is gained in the real random delayed-choice erasure experiment of Kim et al. (Phys. Rev. Lett. 84:1–5, 2000) by a relative-reality-of-unitarily-evolving-state (RRUES) approach (explained in the first part). Finally, it is (...) shown that this remarkable experiment, which performs, by random choice, two incompatible measurements at the same time, is actually an EPR-type disentanglement experiment, closely related to the micromaser experiment discussed in the first part. (shrink)

The concept of retroactive apparent occurrence, the main ingredient of Wheeler's delayed-choice thought experiments, is systematically incorporated into the quantum theory of measurement (in the framework of the recent review of Busch, Lahti, and Mittelstaedt). Besides, the (general) notion of individual-system measurement is introduced, and, due to it, premeasurement is defined by a truly minimal condition. Finally, retroactive apparent occurrence is made use of to derive apparent objectification in measurement. The derivation is discussed in the framework of the quantum mechanical (...) approach to the objectification problem. (shrink)