Some typical Gedanken experiments in quantum mechanics are discussed in a modified form involving phenomenological electrodynamics for their explanation. The examples discussed are: (i) a two-slit experiment with photons, the difference from the standard situation being that two dielectric rods are assumed as photon detectors, (ii) a weighing experiment of a light pulse contained within a dielectric medium (a modified version of the Einstein-Bohr experiment) and (iii) a two-slit experiment in a dielectric environment.
Some typical Gedanken experiments in quantum mechanics are discussed in a modified form involving phenomenological electrodynamics for their explanation. The examples discussed are: (i) a two-slit experiment with photons, the difference from the standard situation being that two dielectric rods are assumed as photon detectors, (ii) a weighing experiment of a light pulse contained within a dielectric medium (a modified version of the Einstein-Bohr experiment) and (iii) a two-slit experiment in a dielectric environment.
Abstract The famous gedanken experiments of quantum mechanics have played crucial roles in developing the Copenhagen interpretation. They are studied here from the perspective of standard quantum mechanics, with no ontological interpretation involved. Bohr's investigation of these gedanken experiments, based on the uncertainty relation with his interpretation, was the origin of the Copenhagen interpretation and is still widely adopted, but is shown to be not consistent with the quantum mechanical view. We point out that in most of these gedanken experiments, entanglement plays a crucial role, while its buildup does not change the uncertainty of the concerned quantity in the way thought by Bohr. Especially, in the gamma ray microscope and recoiling double‐slit gedanken experiments, we expose the entanglement based on momentum exchange. It is shown that even in such cases, the loss of interference is only due to the entanglement with other degrees of freedom, while the uncertainty relation argument, which has not been questioned up to now, is not right.
Delaying Quantum Choice Photons can display wavelike or particle-like behavior, depending on the experimental technique used to measure them. Understanding this duality lies at the heart of quantum mechanics. In two reports, Peruzzo et al. (p. 634 ) and Kaiser et al. (p. 637 ; see the Perspective on both papers by Lloyd ) perform an entangled version of John Wheeler's delayed-choice gedanken experiment, in which the choice of detection can be changed after a photon passes through a double-slit to avoid the measurement process affecting the state of the photon. The original proposal allowed the wave and particle nature of light to be interchanged after the light had entered the interferometer. By contrast in this study, entanglement allowed the wave and particle nature to be interchanged after the light was detected and revealed the quantum nature of the photon, for example, it displays wave- and particle-like behavior simultaneously.
Abstract 1. In the general synthesis of classical dynamics with the quantum theory, the Uncertainty Principle plays a most useful part. It is of course only one aspect of the new mechanics, but it is a very helpful one since by its means it becomes easy to see where the old classical ideas broke down. The state of affairs in the quantum theory is not unlike that of the early days of relativity, when most of those who studied the subject felt the need of supporting the formal theory by seeing how the old ideas failed in specific cases. Here the formal theory is very abstract and is not easy to follow intuitively, and the Uncertainty Principle plays much the same rôle as did the examples of clocks and rods in relativity theory. For this reason it is more appropriate for illustrative examples, than for any extreme generality, and though a number of examples have been already given by Heisenberg and Bohr, it may not be amiss to have some more. There are probably some who will have shared my experience that it is often by no means easy to detect how the uncertainty enters into a given experiment, though once detected the arguments are usually very simple. In a recent conversation Professor Bohr criticised some rather careless remarks that I had made, and the present work was undertaken to clear matters up. It may be shortly described as a study of the Uncertainty Principle in connection with electrometers and magnetometers. It may be of interest to point out that the Uncertainty Principle can be regarded from a rather different aspect. The "resolving power" of optical instruments was discussed very fully by Rayleigh on wave principles, but as long as matter was regarded in the classical manner, a mechanical instrument could be considered as capable of measuring quantities with absolute accuracy. Now that we know that matter also has wave properties, there is need of a theory of the resolving power of mechanical instruments, and this is exactly what the Uncertainty Principle supplies.
The previous chapter surveyed part of the rich variety of physical phenomena that can be understood using the ideas of quantum physics. Now that we are beginning the task of looking more deeply into the subject we shall find it useful to concentrate on examples that are comparatively simple to understand but which still illustrate the fundamental principles and highlight the basic conceptual problems. Some years ago most writers discussing such topics would probably have turned to the example of a ‘particle’ passing through a two-slit apparatus (as in Figure 1.2), whose wave properties are revealed in the interference pattern. Much of the discussion would have been in terms of wave–particle duality and the problems involved in position and momentum measurements, as in the discussion of the uncertainty principle in the last chapter. However, there are essentially an infinite number of places where the particle can be and an infinite number of possible values of its momentum, and this complicates the discussion considerably. We can illustrate all the points of principle we want to discuss by considering situations where a measurement has only a small number of possible outcomes. One such quantity relating to the physics of light beams and photons is known as polarisation . In the next section we discuss it in the context of the classical wave theory of light, and the rest of the chapter extends the concept to situations where the photon nature of light is important.
The previous chapter surveyed part of the rich variety of physical phenomena that can be understood using the ideas of quantum physics. Now that we are beginning the task of looking more deeply into the subject we shall find it useful to concentrate on examples that are comparatively simple to understand but which still illustrate the fundamental principles and highlight the basic conceptual problems. Some years ago most writers discussing such topics would probably have turned to the example of a ‘particle’ passing through a two-slit apparatus (as in Figure 1.2), whose wave properties are revealed in the interference pattern. Much of the discussion would have been in terms of wave–particle duality and the problems involved in position and momentum measurements, as in the discussion of the uncertainty principle in the last chapter. However, there are essentially an infinite number of places where the particle can be and an infinite number of possible values of its momentum, and this complicates the discussion considerably. We can illustrate all the points of principle we want to discuss by considering situations where a measurement has only a small number of possible outcomes. One such quantity relating to the physics of light beams and photons is known as polarisation . In the next section we discuss it in the context of the classical wave theory of light, and the rest of the chapter extends the concept to situations where the photon nature of light is important.
Section I.- Theoretical Implications of Time-Dependent Double Resonance Neutron Interferometry.- Calculations in the Causal Interpretation of Quantum Mechanics.- Calculation of Amplification Processes Generated by Empty Quantum Waves.- Relative Metrics and Physical Models for Non-local Particles.- A Two-Fluid Vacuum, the Photex, and the Photex-Photon Connection.- Discussion I.- Section II.- Summary of F. De Martini's Paper, Testing of Particle Distinguish-ability with Laser Interference Experiments.- Toward a Causal Interpretation of the Relativistic Quantum Mechanics of a Spinning Particle.- Nonlinear Behaviour of Light at Very Low Intensities: The Photon Clump Model.- Geometry-Dependent Predictions of the Quantum Potential Model for the Anomalous Photoelectric Effect.- EPR-Type Experiments and Enhanced Photon Detection.- Discussion II.- Section III.- Stochastic Optics: Wave-Particle Duality Without Particles.- Neo-Hertzian Electromagnetism.- Effective Photon Hypothesis vs. Quantum Potential Theory: Theoretical Predictions and Experimental Verification.- Compositeness of Photons and Its Implications.- Logical Meanings in Quantum Mechanics for Axioms and for Imaginary and Transfinite Numbers and Exponentials.- The Aharonov-Bohn Effect and the Quantum Interference Phase Shift due to an Electrostatic Field.- Discussion III.- Section IV.- Critical Analysis of the Tests of Local Realism Versus Quantum Mechanics.- Physical Photons: Theory, Experiment and Implications.- The Theoretical Nature of a Photon in a Lattice Vacuum.- Is the Photon Concept Really Necessary?.- Beyond Quantum Mechanics Using the Subvac.- Discussion IV.- Section V.- Does Quantum Electrodynamics Explain the Observed Lamb Shift?.- The Quantum and Rest Frame Vacuum - Absolute Motion with Lorentz Covariance.- The Double Slit Experiment and the Nonergodic Interpretation of Quantum Mechanics.- Einstein's Conception of the Ether and Its Up-To-Date Applications in the Relativistic Wave Mechanics.- Discussion V.- Section VI.- Concluding Remarks.- Concluding Remarks.- Comments.- Photo.- Conference Participants and Observers.