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Tuesday, April 08, 2025
10:30 AM - 11:30 AM
CNLS Conference Room (TA-3, Bldg 1690)

Seminar

A simple, practical experiment to investigate atomic wavefunction reduction within a Stern-Gerlach magnet.

Michael Devereux

For nearly one hundred years our quantum-mechanics texts have depicted a continuous, spin-directionsuperposition of the wavefunction of the silver atom traversing a Stern-Gerlach magnet. ButSchrodinger’s equation for that time-independent potential is separable, implying discontinuity inquantum wavefunction development there, resulting in a single atomic trajectory of wavepacketevolution, not a superpositon. Long ago Bohm and Wigner suggested an extended S-G experiment withadditional bending magnets whose putative, anticipated interference pattern was thought to confirm a spin-direction superposition. Schwinger, Englert, and Scully showed that particular experiment to be impractical. Here I’ll describe a remarkably simple, practical experiment, using a micro-fabricated slit screen, instead of bending magnets, to look for that supposed interference. Because the Stern-Gerlach experiment is our prototype for quantum measurement, there are seminal, significant consequences of a realistic appreciation of wavefunction evolution through the S-G magnet. They include questions of the validity of the de Broglie-Bohm interpretation, of “Quantum Erasure”, and a possible explanation, after repeated, unsuccessful attempts, of the Frisch-Segre experiment from 1933.

[1] J. Phys. B, 57 152501 (2024)

Bio: I received my physics PhD from New Mexico State U, while helping to build, operate, and analyze experiments with the EPICS pion spectrometer here at LANL. I subsequently worked at the Swiss Technical University near Zurich on muonium experiments, and other elementary-particle measurements. Since then I've taught at Earlham College in Indiana, and the School of Mines in Colorado. I’ve also occasionally been a visiting scientist here. I’m now a retired physics researcher with an abiding (not to say consuming) interest in quantum measurement. I've published several other articles on the subject.

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Host: Cristiano Nisoli (T-4) and James Colgan (LDRD, acting)