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arXiv:1907.06707

Position measurement-induced collapse states: Proposal of an experiment

Moncy V. John, Kiran Mathew

Published Jul 15, 2019• 0 citations
arXivHTMLPDF

Abstract

The quantum mechanical treatment of diffraction of particles, based on the standard postulates of quantum mechanics and the postulate of existence of quantum trajectories, leads to the `position measurement-induced collapse' (PMIC) states. An experimental set-up to test these PMIC states is proposed. The apparatus consists of a modified Lloyd's mirror in optics, with two reflectors instead of one. The diffraction patterns for this case predicted by the PMIC formalism are presented. They exhibit quantum fractal structures in space-time called `quantum carpets', first discovered by Berry (1996). The PMIC formalism in this case closely follows the `boundary bound diffraction' analysed in a previous work by Tounli, Alverado and Sanz (2019). In addition to obtaining their results, we have shown that the time evolution of these collapsed states also leads to Fresnel and Fraunhofer diffractions. It is anticipated that the verification of PMIC states by this experiment will help to better understand collapse of the wave function during quantum measurements.

DOI
10.48550/arxiv.1907.06707

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The quantum mechanical treatment of diffraction of particles, based on the standard postulates of quantum mechanics and the postulate of existence of quantum trajectories, leads to the position measurement-induced collapse' (PMIC) states. An experimental set-up to test these PMIC states is proposed. The apparatus consists of a modified Lloyd's mirror in optics, with two reflectors instead of one. The diffraction patterns for this case predicted by the PMIC formalism are presented. They exhibit quantum fractal structures in space-time called quantum carpets', first discovered by Berry (1996). The PMIC formalism in this case closely follows the `boundary bound diffraction' analysed in a previous work by Tounli, Alverado and Sanz (2019). In addition to obtaining their results, we have shown that the time evolution of these collapsed states also leads to Fresnel and Fraunhofer diffractions. It is anticipated that the verification of PMIC states by this experiment will help to better understand collapse of the wave function during quantum measurements.
This paper proposes an experiment designed to distinguish between competing interpretations of quantum mechanics: those that involve wave function collapse and those that assume purely unitary evolution. The experiment tests whether an observer can measure a system without collapsing its wave function. To this end, we introduce the concept of an unconscious observer, defined by two criteria: (1) It measures a quantum system and sets the state of another system based on the result. (2) It allows an external experimentalist to infer the measurement outcome by examining the observer's state. The more distinguishable the observer's resulting states, the more it resembles a conventional measurement apparatus. Using weak measurements, the experimentalist probes these states, thereby testing the second criterion. The interference patterns observed in this setup reveal whether collapse has occurred, allowing experimental discrimination between collapse-based and unitary interpretations.
Quantum mechanics predicts measurement outcomes with remarkable accuracy, yet it does not identify the physical mechanism that produces them. Standard formalisms treat collapse as an external postulate or an informational update, leaving the origin of measurement undefined. This paper develops a substrate-based account in which measurement arises from the structural properties of mass rather than from observation, information, or consciousness. Within the Quantum Substrate Dynamics (QSD) framework, all stable matter possesses a finite coherence envelope and participates in discrete Causality Intervals (CIs) that bound how the substrate can reconfigure. Massless excitations such as photons do not possess coherence envelopes and therefore cannot induce or modify collapse; they only traverse the geometric constraints imposed by nearby mass-phase structures.From this asymmetry, a coherent picture of measurement emerges. Collapse occurs when the envelope of a mass-phase structure overlaps a propagating excitation and enforces local CI pacing and curvature--compliance limits, defining which outcomes are structurally supportable. This mechanism reproduces the behavior of detectors, the material dependence of diffraction, the emergence of interference patterns only at mass-phase boundaries, and the well-established fact that light beams in free space do not interact. Classical paradoxes: Wigner's friend, Schrodinger's cat, contextuality, and delayed-choice interference are resolved without invoking global wavefunctions, observer-dependent realities, or branching worlds.The result is a fully physical, mass-induced account of quantum measurement. Collapse becomes a structural re-lock within the substrate rather than an epistemic update or interpretational supplement. This framework preserves the successful predictions of quantum theory while supplying the missing mechanism: observation is not a special act, but the structural consequence of mass interacting with serialized, massless propagations under finite substrate throughput.Version 2 Revision:The title and abstract have been updated to improve clarity and better reflect the paper’s central mechanism. No changes have been made to the analysis or conclusions.
In a seminal paper, Abbott et al. analyzed the relationship between a particle's trajectory and the resolution of position measurements performed by an observer at fixed time intervals. They predicted that quantum paths exhibit a universal Hausdorff dimension that transitions from d=2d=2d=2 to d=1d=1d=1 as the momentum of the particle increases. However, although measurements were assumed to occur at intervals of time, the calculations only involved evaluating the expectation value of operators for the free evolution of wave function within a single interval, with no actual physical measurements performed. In this work we investigate how quantum measurements alter the fractal geometry of quantum particle paths. By modelling sequential measurements using Gaussian wave packets for both the particle and the apparatus, we reveal that the dynamics of the measurement change the roughness of the path and shift the emergent Hausdorff dimension towards a lower value in nonselective evolution. For selective evolution, feedback control forces must be introduced to counteract stochastic wave function collapse, stabilising trajectories and enabling dimensionality to be tuned. When the contribution of the measurement approaches zero, our result reduces to that of Abbott et al. Our work can thus be regarded as a more realistic formulation of their approach, and it connects theoretical quantum fractality with measurement physics, quantifying how detectors reshape spacetime statistics at quantum scales.
Quantum mechanics is an extremely successful theory that agrees with every experimental test. However, the principle of linear superposition, a central tenet of the theory, apparently contradicts a commonplace observation: macroscopic objects are never found in a linear superposition of position states. Moreover, the theory does not explain why during a quantum measurement, deterministic evolution is replaced by probabilistic evolution, whose random outcomes obey the Born probability rule. In this article a review is given of an experimentally falsifiable phenomenological proposal, known as continuous spontaneous collapse: a stochastic nonlinear modification of the Schr\"odinger equation, which resolves these problems, while giving the same experimental results as quantum theory in the microscopic regime. Two underlying theories for this phenomenology are reviewed: trace dynamics and gravity-induced collapse. As the macroscopic scale is approached, predictions of this proposal begin to differ appreciably from those of quantum theory and are being confronted by ongoing laboratory experiments that include molecular interferometry and optomechanics. These experiments, which test the validity of linear superposition for large systems, are reviewed here, and their technical challenges, current results, and future prospects summarized. It is likely that over the next two decades or so, these experiments can verify or rule out the proposed stochastic modification of quantum theory.