Heisenberg in 1929 introduced the “collapse of the wavepacket” into quantum theory. We review here an experiment at Berkeley which demonstrated several aspects of this idea. In this experiment, a pair of daughter photons was produced in an entangled state, in which the sum of their two energies was equal to the sharp energy of their parent photon, in the nonlinear optical process of spontaneous parametric down-conversion. The wavepacket of one daughter photon collapsed upon a measurement-at-a-distance of the other daughter's energy, in such a way that the total energy of the two-photon system was conserved. Heisenberg's energy-time uncertainty principle was also demonstrated to hold in this experiment.
Standard interpretations of the quantum double-slit experiment rely on non-local wave-function collapse, single-particle self-interference across multiple apertures simultaneously, or retrocausal mechanisms. In this paper, I propose a strictly local, causal thought experiment in which individual quanta propagate as spatially extended, cohesive wavepackets carrying localized forward momentum. In my framework, a single wavepacket traverses only one aperture at a time by undergoing rotational boundary-wall scattering at the slit edges, while transferring its momentum to a single impact point on the detector screen and embedding a temporary spatial phase imprint ("skid mark") into the local quantum surface. Subsequent quanta of identical wavelength absorb and interact with the immediately preceding surface imprint, modifying their peak-and-trough trajectory distribution and overwriting the surface state in a strictly one-by-one sequential (Markovian) relay. Furthermore, I preemptively address key theoretical objections—including special-relativistic speed-of-light constraints, classical momentum transfer mechanics, non-local entanglement signaling paradoxes, planetary motion in local reference frames, and multi-wavelength cross-talk—demonstrating a self-consistent local-realist framework.
Standard interpretations of the quantum double-slit experiment rely on non-local wave-function collapse, single-particle self-interference across multiple apertures simultaneously, or retrocausal mechanisms. In this paper, I propose a strictly local, causal thought experiment in which individual quanta propagate as spatially extended, cohesive wavepackets carrying localized forward momentum. In my framework, a single wavepacket traverses only one aperture at a time by undergoing rotational boundary-wall scattering at the slit edges, while transferring its momentum to a single impact point on the detector screen and embedding a temporary spatial phase imprint ("skid mark") into the local quantum surface. Subsequent quanta of identical wavelength absorb and interact with the immediately preceding surface imprint, modifying their peak-and-trough trajectory distribution and overwriting the surface state in a strictly one-by-one sequential (Markovian) relay. Furthermore, I preemptively address key theoretical objections—including special-relativistic speed-of-light constraints, classical momentum transfer mechanics, non-local entanglement signaling paradoxes, planetary motion in local reference frames, and multi-wavelength cross-talk—demonstrating a self-consistent local-realist framework.