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arXiv:1210.0432

On the question of wavefunction collapse in a double-slit diffraction experiment

Fotini Pallikari

Published Oct 1, 2012• 4 citations
arXivHTMLPDF

Abstract

It was recently proposed that the fringe visibility in the interference pattern of a double-slit diffraction experiment with a HeNe laser beam was reduced as a consequence of the focused attention of participants on the double-slit that initiated the collapse of the photon wavefunction. A thorough examination of the reported apparatus and diffraction pattern data is presented here revealing a number of inconsistencies in the experimental setup. The hypothesis for wavefunction collapse under the proposed experimental conditions is found problematic as the use of single photon sources is demanded.

DOI
10.48550/arxiv.1210.0432

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It was recently proposed that the fringe visibility in the interference pattern of a double-slit diffraction experiment with a HeNe laser beam was reduced as a consequence of the focused attention of participants on the double-slit that initiated the collapse of the photon wavefunction. A thorough examination of the reported apparatus and diffraction pattern data is presented here revealing a number of inconsistencies in the experimental setup. The hypothesis for wavefunction collapse under the proposed experimental conditions is found problematic as the use of single photon sources is demanded.
An experiment was conducted to explore possible psychophysical influences on interference patterns generated by an optical double-slit system. The experiment was motivated by a proposed explanation of the quantum measurement problem by John von Neumann and others, namely that consciousness collapses the quantum wavefunction. The study design generated a single database partitioned into eight differential tests, four in experimental conditions where participants alternately directed their attention toward and away from the optical system, and four in sham conditions when no one was present. The planned analysis was comparison of means in attention-toward vs. attention-away conditions; a secondary analysis added later, but before the data were examined, was comparison of variances. After adjusting the eight mean comparisons for multiple testing, none were statistically significant, but one of the eight variance differences was suggestively significant.To date, 11 of 28 conceptual replications of this experiment, reported by four independent teams, have reported statistically significant outcomes (p < 0.05, two-tail), where only one would be expected by chance. Given the implications of psychophysical effects on our understanding of the role of consciousness in the physical world, we encourage others to attempt to replicate this experiment.
3.1 Interference of a Single Photon The kinds of study originally conducted by Thomas Young - in particular, the celebrated "double slit" experiment that we briefly examined in Chapter 1 (see Fig. 1) - provide a capacity to reveal far more than the wave nature of light, important as that is. True enough, the observed characteristic fringe pattern, when monochromatic light passes through two closely spaced slits onto a screen, appears to be simply explicable on the basis of waves from each slit undergoing constructive and destructive interference at different positions on the screen. Yet, astonishingly, these patterns of interference are still exhibited when individual photons of a low-intensity input beam reach the screen one at a time, showing that it cannot in fact be a matter of different photons having to interfere with each other. Indeed, Dirac enunciated the general principle that photons can never directly interact with each other. The double slit and other such experiments indicate that each photon interacts in a delocalized, wave-like manner with both slits at the same time. Successive experiments build interference patterns that conform to an exact mathematical distribution formula, but the position at which an individual photon is detected in any particular instance cannot be predicted; this is a quintessential illustration of quantum uncertainty. Using the path integral approach of quantum theory, the phenomenon is more accurately represented by introducing a summation over all possible routes between the source and the screen on which the pattern appears, signifying an entire "lifetime" for each photon involved in the experiment. This relates to the fact that the actual trajectory is unknown without an observation, and thus we only obtain the probabilities of the photon striking the screen at different positions and times; all trajectories (potentialities) must be considered in a superposition. Each route is considered equally probable, and the variation in phase produces quantum interference. The differences in phase of each trajectory, at varying positions on the screen, generates the fringe pattern. An intriguing variation on this experiment involves "marking" the photons so that the actual route of each photon to the screen is known. Remarkably, in such a case, the fringe patterns do not appear because quantum interference cannot occur. A consequence of the observation of the photon route is an effect that, in other quantum mechanical connections, is known as a collapse of the wavefunction. However, it is possible for the fringe patterns to reappear when information on the route of the photons is lost; this is known as a quantum eraser.
A double-slit optical system was used to test the possible role of consciousness in the collapse of the quantum wavefunction. The ratio of the interference pattern's double-slit spectral power to its single-slit spectral power was predicted to decrease when attention was focused toward the double slit as compared to away from it. Each test session consisted of 40 counterbalanced attention-toward and attention-away epochs, where each epoch lasted between 15 and 30 s. Data contributed by 137 people in six experiments, involving a total of 250 test sessions, indicate that on average the spectral ratio decreased as predicted (z=-4:36, p=6*10-6). Another 250 control sessions conducted without observers present tested hardware, software, and analytical procedures for potential artifacts; none were identified (z=0:43, p=0:67). Variables including temperature, vibration, and signal drift were also tested, and no spurious influences were identified. By contrast, factors associated with consciousness, such as meditation experience, electrocortical markers of focused attention, and psychological factors including openness and absorption, significantly correlated in predicted ways with perturbations in the double-slit interference pattern. The results appear to be consistent with a consciousness-related interpretation of the quantum measurement problem.