A mesoscopic Stern-Gerlach device

M. I. Shirokov

Marco Frasca

Stern-Gerlach experiment is a paradigm of measurement theory in quantum mechanics. Notwithstanding several analysis given in literature, no clear understanding of the apparent collapse has been given so far. Indeed, one can imagine a Stern-Gerlach device where all environmental effects are removed and ask the question on how the measurement goes on. In this letter we will prove that a the Stern-Gerlach device behaves as a true measurement apparatus, as expected by the Copenaghen interpretation, by the Ehrenfest theorem. In this way we recover, by other means, a limit on the Stern-Gerlach device, given by Bohm, based on scrambling of phases due to a large oscillation frequency.

Marlan O. Scully, Willis E. Lamb, Asım Orhan Barut

Kevin Melin, Pavel Nagornykh, Yu Shan Lu +3 more

M. Steiner, Michael R. Frey, ARMEN M. GULIAN +2 more

The Stern-Gerlach (SG) apparatus for measuring the spin of an uncharged spin-1/2 particle is the archetypal quantum sensing device. We study this device for the new problem of measuring the spin of a particle that is coupled externally to another particle. Specifically, we treat two coupled particles in which a single particle is measured by the SG device while the other is not. We show simulations of how the binding energy associated with the external coupling is completely converted to potential energy and kinetic energy as the single particle separates spatially within the magnetic field of the SG device. Additionally we show simulations of how the initial particle acceleration within the SG devices relates to the coupling, the quantum state of the two-particle system, and the initial spatial dispersion of the particle within the SG device. The results of our analysis, though obtained specifically for the SG apparatus, may be generic to other quantum measurement devices with similar external coupling.

Bipin R. Desai