A Transactional Analysis of Quantum Interaction-Free Measurements

J. G. Cramer

Avshalom C. Elitzur, Shahar Dolev

Cramer’s analysis of interaction‐free measurement in terms of his Transactional Interpretation is critically reviewed. Next we attempt to apply it to some varieties of IFM that have been devised during the last decade, pointing out the challenges posed by such attempt We then discuss the possible bearings of these experiments on the Transactional Interpretation as well as on the nature of spacetime.

Yong-Yi Huang

Onofrio L. Russo, Liang Jiang

J. G. Cramer

In 1993 Elitzur and Vaidmannl (EV) demonstrated that quantum mechanics permits the use of light quanta to examine an object without a single photon having actually interacted with the object, requiring only the possibility of such an interaction. The EV scenario has recently been carried out in the laboratory and its predictions verified. EV discussed their scenario in terms of the Copenhagen interpretation of quantum mechanics, in which the interaction-free result is rather mysterious, using a “knowledge” not available classically. They also used the Everett-Wheeler interpretation and suggested that the information indicating the presence of the opaque object comes from an interaction in a separate Everett-Wheeler universe, with the information communicated to our universe through the absence of interference. In the present work, we will examine the EV interaction-free scenario in terms of the transactional interpretation of quantum mechanics2 and will provide a more plausible account of the physical processes that make possible quantum interaction-free measurements.

Louis Marchildon

The transactional interpretation of quantum mechanics, following the time-symmetric formulation of electrodynamics, uses retarded and advanced solutions of the Schrodinger equation and its complex conjugate to understand quantum phenomena by means of transactions. A transaction occurs between an emitter and a specific absorber when the emitter has received advanced waves from all possible absorbers. Advanced causation always raises the specter of paradoxes, and it must be addressed carefully. In particular, different devices involving contingent absorbers or various types of interaction-free measurements have been proposed as threatening the original version of the transactional interpretation. These proposals will be analyzed by examining in each case the configuration of absorbers and, in the special case of the so-called quantum liar experiment, by carefully following the development of retarded and advanced waves through the Mach-Zehnder interferometer. We will show that there is no need to resort to the hierarchy of transactions that some have proposed, and will argue that the transactional interpretation is consistent with the block-universe picture of time.