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arXiv:2307.14687 · Quantum Studies Mathematics and Foundations

Delayed choice experiments: an analysis in forward time

Marijn Waaijer, Jan van Neerven

Published Mar 25, 2024• 1 citation
arXivHTMLPDF

Abstract

Abstract In this article, we present a detailed analysis of two famous delayed choice experiments: Wheeler’s classic gedanken-experiment and the delayed quantum eraser. Our analysis shows that the outcomes of both experiments can be fully explained on the basis of the information collected during the experiments using textbook quantum mechanics only. At no point in the argument, information from the future is needed to explain what happens next. In fact, more is true: for both experiments, we show, in a strictly mathematical way, that a modified version in which the time-ordering of the steps is changed to avoid the delayed choice leads to exactly the same final state. In this operational sense, the scenarios are completely equivalent in terms of conclusions that can be drawn from their outcomes.

DOI
10.1007/s40509-024-00328-5

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Abstract In this article, we present a detailed analysis of two famous delayed choice experiments: Wheeler’s classic gedanken-experiment and the delayed quantum eraser. Our analysis shows that the outcomes of both experiments can be fully explained on the basis of the information collected during the experiments using textbook quantum mechanics only. At no point in the argument, information from the future is needed to explain what happens next. In fact, more is true: for both experiments, we show, in a strictly mathematical way, that a modified version in which the time-ordering of the steps is changed to avoid the delayed choice leads to exactly the same final state. In this operational sense, the scenarios are completely equivalent in terms of conclusions that can be drawn from their outcomes.
This work examines the well-known delayed choice Quantum Eraser experiment carried out by Kim et al in 2000 from the standpoint of Classical Physics. I've drawn a diagram of the experiment's setup. I show that the experiment's outcome can be explained using Classical Physics, and that it does not require "spooky action at a distance" owing to entangled particles, as Einstein famously put it, nor events changing the past due to the experiment's delayed choice feature.
The delayed-choice experiment and the quantum eraser experiment are two of the most challenging interpretive problems in quantum mechanics. Standard textbook accounts trace the presence or absence of interference to whether the experimenter "knows" the photon's path — a causal framework implying backward-in-time influence. This article offers an intuitive, diagram-rich account grounded in the wave-or-particle geometric framework, revealing that both experiments share a far simpler backbone: interference depends solely on how many waves reach a given detector. One wave → no interference. Two waves → interference. This conclusion alters no mathematical prediction of quantum mechanics; it merely flips the causal arrow from "knowing the path destroys interference" to "the number of waves creates interference." A forthcoming main paper will present the complete three-column correspondence (experimental step → geometry → QFT standard) with full algebraic verification.
Abstract: Recently the experimental group of A. Aspect published a very interesting experimental realization of the well known Wheeler’s delayed-choice Gedanken Experiment. In the paper the authors refer to the usual, non causal linear explanation of the experiment. In the present work we show how it is possible, and furthermore desirable, to explain the same experiment in terms of the modern local causal and nonlinear quantum theory, inspired in the work of the great physicist Louis de Broglie. In this way we are able to get rid of the mysteries and of the weird features of the orthodox interpretation, like retractions in time, and therefore recover causality and rationality once more.
This paper discusses the well-known delayed choice Quantum Eraser experiment performed by Kim et al. in 2000 and analyzes it from a Classical Physics perspective. I have included a diagram of the setup used in the experiment. I show that the result of the experiment can be explained by Classical Physics and does not require “Spooky action at a distance” due to entangled particles, as Einstein famously once put it, nor events modifying the past due to the delayed choice aspect of the experiment.
John Wheeler devised a gedanken experiment in which a piece of apparatus can be altered just before the arrival of particle, and this “delayed choice ” can, seemingly, alter the quantum state of the particle at a much earlier time, long before the choice is made. A slightly different gedanken experiment, which exhibits the same conceptual difficulty, is analyzed using the techniques of consistent history quantum theory. The idea that the future influences the past disappears when proper account is taken of the diversity of possible quantum descriptions of the world, and their mutual compatibility or incompatibility. John Wheeler proposed a delayed-choice experiment in which the second beam splitter of a Mach-Zehnder interferometer is or is not removed at the very last instant before a photon reaches it and passes out of the interferometer [1]. A modified version which exhibits essentially the same paradox is shown in Fig. 1. A photon enters the interferometer through channel a, and two detectors in the c and d arms are either (a) left in position, or (b) removed just before the photon reaches (one of) them, so that it is free to proceed on to the second
Abstract The delayed-choice quantum eraser has long been a subject of controversy, and has been looked at as being incomprehensible to having retro-causal effect in time. Here the delayed-choice quantum eraser is theoretically analyzed using standard quantum mechanics. Employing a Mach–Zehnder interferometer, instead of a conventional two-slit interference, brings in surprising clarity. Some common mistakes in interpreting the experiment are pointed out. It is demonstrated that in the delayed mode there is no which-way information present after the particle is registered on the screen or the final detectors, contrary to popular belief. However, it is shown that another kind of path information is present even after the particle is registered in the final detectors. The registered particle can be used to predict the results of certain yet to be made measurements on the which-way detector. This novel correlation can be tested in a careful experiment. It is consequently argued that there is no big mystery in the experiment, and no retro-causal effect whatsoever.