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Fortschritte der Physik

Momentum changes due to quantum localization

A.J. Short

Published Apr 24, 2003• 3 citations
Publisher

Abstract

Abstract The momentum changes caused by localization are a central feature of wave‐particle duality. Investigating these changes in more detail, we find that single‐slit diffraction relies on a form of `interaction‐free' scattering, and that an ideal which‐way measurement can be made without any back‐reaction on the detector. We also consider Kim and Shih's recent realization of Popper's experiment, involving diffraction of entangled particles, and offer an explanation for the results.

DOI
10.1002/prop.200310067

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Momentum kicks due to quantum localization

Short, A. J.

The momentum changes caused by position measurements are a central feature of wave-particle duality. Here we investigate two cases - localization by a single slit, and which-way detection in the double-slit interference experiment - and examine in detail the associated momentum changes. Particular attention is given to the transfer of momentum between particle and detector, and the recoil of the measuring device. We find that single-slit diffraction relies on a form of `interaction-free' scattering, and that an ideal which-way measurement can be made without any back-reaction on the detector.

arXiv:quant-ph/0112121•Dec 20, 2001•0 citations

Realism in the Realized Popper’s Experiment

Geoffrey Hunter

The realization of Karl Popper’s EPR‐like experiment by Shih and Kim (published 1999) produced the result that Popper hoped for: no “action at a distance” on one photon of an entangled pair when a measurement is made on the other photon. This experimental result is interpretable in local realistic terms: each photon has a definite position and transverse momentum most of the time; the position measurement on one photon (localization within a slit) disturbs the transverse momentum of that photon in a non‐predictable way in accordance with the uncertainty principle; however, there is no effect on the other photon (the photon that is not in a slit) no action at a distance. The position measurement (localization within a slit) of the one photon destroys the coherence (entanglement) between the photons; i.e. decoherence occurs. This realistic (albeit retrodictive) interpretation of the Shih‐Kim realization of what Popper called his “crucial experiment” is in accord with Bohr’s original concept of the nature of the uncertainty principle, as being an inevitable effect of the disturbance of the measured system by the measuring apparatus. In this experiment the impact parameter of an incident photon with the centerline of the slit is an uncontrollable parameter of each individual photon scattering event; this impact parameter is variable for every incident photon, the variations being a statistical aspect of the beam of photons produced by the experimental arrangement. These experimental results are also in accord with the proposition of Einstein, Podolski and Rosen’s 1935 paper: that quantum mechanics provides only a statistical, physically incomplete, theory of microscopic physical processes, for the quantum mechanical description of the experiment does not describe or explain the individual photon scattering events that are actually observed; the angle by which an individual photon is scattered is not predictable, because the photon’s impact parameter with the centerline of the slit is not observable, and because the electromagnetic interaction between the photon and the matter forming the walls of the slit is not calculable.

arXiv:quant-ph/0507011•AIP conference proceedings•Jan 1, 2002•4 citations

Realism in the Realized Popper's Experiment

Geoffrey Hunter

The realization of Karl Popper's experiment by Shih and Kim (published 1999) produced the result that Popper hoped for: no ``action at a distance'' on one photon of an entangled pair when a measurement is made on the other photon. This experimental result is interpretable in local realistic terms: each photon has a definite position and transverse momentum most of the time; the position measurement on one photon (localization in a slit) disturbs the transverse momentum of that photon in a non-predictable way in accordance with the uncertainty principle; however, there is no effect on the other photon (the photon that is not in a slit) no action at a distance. The position measurement (localization within a slit) of the one photon destroys the coherence (entanglement) between the photons; i.e. decoherence occurs. This can be understood physically as an electromagnetic interaction between the photon in the slit and the electrons of the atoms in the surface of the solid that forms the slit.

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Quantum physics of entangled systems: Wave‐particle duality and atom‐photon molecules

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Abstract One of the cornerstones of quantum physics is the wave nature of matter. It explains experimentally observed effects like interference and diffraction, occurring when an object moves from one place to another along several indistinguishable ways simultaneously. The wave nature disappears when the individual ways are distinguishable. In this case, the particle nature of the object becomes visible. To determine the particle nature quantitatively, the way of the object has to be measured. Here, large progress has been made recently with new techniques, enabling one to investigate single moving atoms in a controlled manner. Two examples are discussed in the following two sections. The first experiment describes an atom interferometer, where the way of the atom is entangled with its internal state. This allows one to explore the origin of wave‐particle duality and perform a quantitative test of this fundamental principle. The second experiment reports on the observation of an atom‐photon molecule, a bound state between an atom and a single photon. A fascinating aspect of this system is that it makes possible to monitor the motion of a single neutral atom in real time.

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ABSTRACT In this study, we propose a formula to characterize the mechanical properties of microscopic particles from the particle‐wave interaction perspective, defining the corresponding interaction as a velocity‐perpendicular interaction force. Traditional single‐slit diffraction is mainly explained by wave theory and the Huygens–Fresnel principle. However, the single‐photon momentum recoil in diffraction suggests that it is feasible to decouple the particle and wave natures of both photons and the slit, thereby exploring the interaction force between them in depth. We find that photons at different positions inside the slit experience velocity‐perpendicular interaction force, leading to net interaction time differences related to their distances to the slit edges. Based on wave‐particle duality, the modulation quantity formed by the interaction force, net interaction time, slit scale, and Planck constant exerts an on‐off modulation effect. Within this model, photons form clear diffraction fringes, which are rigorously verified to be fully consistent with the Huygens–Fresnel principle. This work provides a dynamical reinterpretation of single‐slit diffraction and establishes a mechanical framework for quantitatively describing quantum phenomena involving particle‐wave interaction.

Annalen der Physik•Jul 1, 2026•0 citations

Reconsidering the Relation Between “Matter Wave Interference” and “Wave–Particle Duality”

Lukas Mairhofer, O. Passon

Abstract Interference of more and more massive objects provides a spectacular confirmation of quantum theory. It is usually regarded as support for “wave–particle duality” and in an extension of this duality even as support for “complementarity”. We first give an outline of the historical development of these notions. Already here it becomes evident that they are hard to define rigorously, i.e. have mainly a heuristic function. Then we discuss recent interference experiments of large and complex molecules which seem to support this heuristic function of “duality”. However, we show that in these experiments the diffraction of a delocalized center-of-mass wave function depends on the interaction of the localized structure of the molecule with the diffraction element. Thus, the molecules display “dual features” at the same time, which contradicts the usual understanding of wave–particle duality. We conclude that the notion of “wave–particle duality” deserves no place in modern quantum physics.

arXiv:2203.08691•Foundations of Physics•Feb 26, 2022•4 citations
Abstract The momentum changes caused by localization are a central feature of wave‐particle duality. Investigating these changes in more detail, we find that single‐slit diffraction relies on a form of `interaction‐free' scattering, and that an ideal which‐way measurement can be made without any back‐reaction on the detector. We also consider Kim and Shih's recent realization of Popper's experiment, involving diffraction of entangled particles, and offer an explanation for the results.
The momentum changes caused by position measurements are a central feature of wave-particle duality. Here we investigate two cases - localization by a single slit, and which-way detection in the double-slit interference experiment - and examine in detail the associated momentum changes. Particular attention is given to the transfer of momentum between particle and detector, and the recoil of the measuring device. We find that single-slit diffraction relies on a form of `interaction-free' scattering, and that an ideal which-way measurement can be made without any back-reaction on the detector.
The realization of Karl Popper’s EPR‐like experiment by Shih and Kim (published 1999) produced the result that Popper hoped for: no “action at a distance” on one photon of an entangled pair when a measurement is made on the other photon. This experimental result is interpretable in local realistic terms: each photon has a definite position and transverse momentum most of the time; the position measurement on one photon (localization within a slit) disturbs the transverse momentum of that photon in a non‐predictable way in accordance with the uncertainty principle; however, there is no effect on the other photon (the photon that is not in a slit) no action at a distance. The position measurement (localization within a slit) of the one photon destroys the coherence (entanglement) between the photons; i.e. decoherence occurs. This realistic (albeit retrodictive) interpretation of the Shih‐Kim realization of what Popper called his “crucial experiment” is in accord with Bohr’s original concept of the nature of the uncertainty principle, as being an inevitable effect of the disturbance of the measured system by the measuring apparatus. In this experiment the impact parameter of an incident photon with the centerline of the slit is an uncontrollable parameter of each individual photon scattering event; this impact parameter is variable for every incident photon, the variations being a statistical aspect of the beam of photons produced by the experimental arrangement. These experimental results are also in accord with the proposition of Einstein, Podolski and Rosen’s 1935 paper: that quantum mechanics provides only a statistical, physically incomplete, theory of microscopic physical processes, for the quantum mechanical description of the experiment does not describe or explain the individual photon scattering events that are actually observed; the angle by which an individual photon is scattered is not predictable, because the photon’s impact parameter with the centerline of the slit is not observable, and because the electromagnetic interaction between the photon and the matter forming the walls of the slit is not calculable.
The realization of Karl Popper's experiment by Shih and Kim (published 1999) produced the result that Popper hoped for: no ``action at a distance'' on one photon of an entangled pair when a measurement is made on the other photon. This experimental result is interpretable in local realistic terms: each photon has a definite position and transverse momentum most of the time; the position measurement on one photon (localization in a slit) disturbs the transverse momentum of that photon in a non-predictable way in accordance with the uncertainty principle; however, there is no effect on the other photon (the photon that is not in a slit) no action at a distance. The position measurement (localization within a slit) of the one photon destroys the coherence (entanglement) between the photons; i.e. decoherence occurs. This can be understood physically as an electromagnetic interaction between the photon in the slit and the electrons of the atoms in the surface of the solid that forms the slit.
Abstract One of the cornerstones of quantum physics is the wave nature of matter. It explains experimentally observed effects like interference and diffraction, occurring when an object moves from one place to another along several indistinguishable ways simultaneously. The wave nature disappears when the individual ways are distinguishable. In this case, the particle nature of the object becomes visible. To determine the particle nature quantitatively, the way of the object has to be measured. Here, large progress has been made recently with new techniques, enabling one to investigate single moving atoms in a controlled manner. Two examples are discussed in the following two sections. The first experiment describes an atom interferometer, where the way of the atom is entangled with its internal state. This allows one to explore the origin of wave‐particle duality and perform a quantitative test of this fundamental principle. The second experiment reports on the observation of an atom‐photon molecule, a bound state between an atom and a single photon. A fascinating aspect of this system is that it makes possible to monitor the motion of a single neutral atom in real time.
ABSTRACT In this study, we propose a formula to characterize the mechanical properties of microscopic particles from the particle‐wave interaction perspective, defining the corresponding interaction as a velocity‐perpendicular interaction force. Traditional single‐slit diffraction is mainly explained by wave theory and the Huygens–Fresnel principle. However, the single‐photon momentum recoil in diffraction suggests that it is feasible to decouple the particle and wave natures of both photons and the slit, thereby exploring the interaction force between them in depth. We find that photons at different positions inside the slit experience velocity‐perpendicular interaction force, leading to net interaction time differences related to their distances to the slit edges. Based on wave‐particle duality, the modulation quantity formed by the interaction force, net interaction time, slit scale, and Planck constant exerts an on‐off modulation effect. Within this model, photons form clear diffraction fringes, which are rigorously verified to be fully consistent with the Huygens–Fresnel principle. This work provides a dynamical reinterpretation of single‐slit diffraction and establishes a mechanical framework for quantitatively describing quantum phenomena involving particle‐wave interaction.
Abstract Interference of more and more massive objects provides a spectacular confirmation of quantum theory. It is usually regarded as support for “wave–particle duality” and in an extension of this duality even as support for “complementarity”. We first give an outline of the historical development of these notions. Already here it becomes evident that they are hard to define rigorously, i.e. have mainly a heuristic function. Then we discuss recent interference experiments of large and complex molecules which seem to support this heuristic function of “duality”. However, we show that in these experiments the diffraction of a delocalized center-of-mass wave function depends on the interaction of the localized structure of the molecule with the diffraction element. Thus, the molecules display “dual features” at the same time, which contradicts the usual understanding of wave–particle duality. We conclude that the notion of “wave–particle duality” deserves no place in modern quantum physics.