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The Experiments

To date, quantum theory has been overwhelmingly confirmed by physical experiments. The need for such a theory in the first place began as the experimental results of the early 1900's could not be explained by contemporary theories. For compactness, I will describe only the quantum interference effects of photons, but note that electrons and neutrons have been observed to display quantum interference as well. Below is a review of three interesting experiments, our understanding of which is controversial. These provide a good survey of the weirdness of QM. In Sections 5 and 7, the ProWave Interpretation is applied to these experiments.

A) The infamous two-slit experiment involves passing light through two slits and allowing the radiation from both slits to diffract and overlap on a distant screen. The interference fringes that are observed are attributed to the wavelike and coherent nature of the photons as they emerge from the slits. If the flux of photons is low enough such that one photon is present in the system at once, then each photon (event) produces only one localized detection at the screen. By integration of many such events, an interference pattern emerges, as predicted by the probability distribution of the wavefunction. Note that if the screen were placed sufficiently close to the slits so as to prevent overlap of diffracted waves from the slits, then each event induces local detection corresponding to the photon having been present at one of the two slits. In this case, the system probability is determined by an incoherent mixture of quantum states, where the quantum states refer to slit passage. The philosophical question raised by this whole experiment is: Does the photon pass through only one slit, or both, or can we even ask this question?

B) The Einstein, Podolsky, Rosen (EPR) Paradox [1] has been the subject of many discussions on quantum interpretations. In 1985, Alain Aspect et. al. measured the polarizations of two correlated photons at various rotation positions of his detectors [3, 4, 5]. Their coincidence count violated Bell's Inequality and experimentally verified that the nonlocal nature of quantum theory is real. The main question here is: How can two particles apparently ``instantaneously'' communicate with each other while being physically separated by an arbitrary distance?

C) In one type of quantum eraser experiment, polarization-correlated photon pairs are emitted in opposite directions [11]. (Refer to Figure 3 later in Section 6.) They are allowed to recombine and interfere at a 50% beam splitter, with detectors at each output port. The apparatus is set up and phase controlled such that both photons of each pair are detected by the same detector, as predicted by QM. Now, a half-wave plate is inserted in one of the paths so as to rotate the polarization by tex2html_wrap_inline289 with respect to the other path. This removes the guarantee of interference at the beam splitter, and it becomes possible to get one ``click'' at each detector from a pair of correlated photons. Building on this further, inserting linear polarizers at tex2html_wrap_inline291 (with respect to each photon path) directly in front of each detector returns the original interference results. It is amazing that we no longer see the effect of the half-wave plate. We have essentially erased its effect. The deepest question raised by this experiment seems to be: Can we affect the nature of the photons in the past by manipulating the present?


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Dan Provenzano
Thu Jan 15 19:33:34 PST 1998