Comments on recent which-way experiments proposed by Scully, Englert, and Walther introducing the idea of quantum erasure

IICQI 2007

Here, we first survey all possible situations of a recent series of Which-Way (WW) experiments proposed by Scully, Englert and Walther introducing the idea of Quantum Erasure (QE). Since their erasing process is a quantum measurement, we argue that all situations of QE can be statistically described by a given joint probability. So it can be easily concluded that the delayed-mode of measurement has no special importance for QE and the time ordering of measurements has no effect too. This is a consequence of the Bayesian rule for the joint probability of two events when the time ordering of the events is arbitrary. We conclude, then, that none of the QE proposals fulfill the bizarre implications of a delayed-choice experiment including the backward causation and the role and meaning of the arrow of time in quantum mechanics. Subsequently, we suggested a new simple experimental arrangement in which the path information could be erased without measurement. Here, the time ordering of detections has a direct effect on the final pattern. Thus the idea of delayed-choice (and its possible interpretations including the backward causation, non-locality and the role of physical reality) is directly introduced here. In interpreting our thought experiment, we argue that whenever one neglects the role of reality assumption in quantum realm, many misleading attitude and misconceptions may arise. In a realistic perspective, however, the state function in quantum mechanics does not completely describe the physical reality. So, the controversial problems, such as the delayed-choice effect, are interpreted subordinately. For example, in Bohm's approach, all of the bizarre aspects of micro world are resolved by considering the real character of particles guided (and influenced) by waves through a quantum potential. We believe that the controversial problems in quantum domain show that the quantum formalism misses some definite elements of physical reality. Correspondingly, our proposed experiment shows that the reality assumption has a primary role in expounding the peculiar features of WW experiments.