Friday, February 14, 2025

Bernstein-Aharonov-Susskind Effect: Observable nonlocal neutron spin

 Bernstein-Aharonov-Susskind Effect

 Aharonov and Susskind (1967) and, independently, Bernstein (1967) predicted the observa-
bility of this 4π-symmetry for interferometric experiments and Eder and Zeilinger (1976) gave the theoretical framework for the neutron interferometric realization. Indeed this 4π-symmetry was known from the beginning of quantum mechanics (Dirac 1930), but it was mostly treated as a non-observable property of spinor quantum mechanics.

 

the 360-degree neutron-rotation experiment was proposed by one of us (Bernstein) in 1967. A similar thought experiment was described almost simultaneously by Yakir Aharonov and Leonard Susskind of Yeshiva University. The experiment demonstrates a highly counterintuitive effect whose mathematical equivalent is the one-sidedness of a Mobius strip. At issue is the spin, or intrinsic angular momentum, of a subatomic particle. According to quantum theory, a neutron or another particle with spin does not return to its initial state when its orientation is rotated through 360 degrees. Instead it takes two full turns, a 720-degree rotation, to restore the state of the particle to its initial condition.

 

 https://www.math.stonybrook.edu/~tony/fb-and-qt/Fiber%20Bundles%20and%20Quantum%20Theory.pdf

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