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Disentanglement of a Singlet Spin State in a Coincidence Stern-Gerlach Device
Umeå University, Faculty of Science and Technology, Department of Chemistry.ORCID iD: 0000-0002-9277-4534
Department of Physical Chemistry, Lund University, Lund, Sweden.
2019 (English)In: Journal of Modern Physics, ISSN 2153-1196, E-ISSN 2153-120X, Vol. 10, no 10, p. 1247-1254Article in journal (Refereed) Published
Abstract [en]

We analyze the spin coincidence experiment considered by Bell in the derivation of Bells theorem. We solve the equation of motion for the spin system with a spin Hamiltonian, Hz, where the magnetic field is only in the z-direction. For the specific case of the coincidence experiment where the two magnets have the same orientation the Hamiltonian Hz commutes with the total spin Iz, which thus emerges as a constant of the motion. Bells argument is then that an observation of spin up at one magnet A necessarily implies spin down at the other B. For an isolated spin system A-B with classical translational degrees of freedom and an initial spin singlet state there is no force on the spin particles A and B. The spins are fully entangled but none of the spin particles A or B are deflected by the Stern-Gerlach magnets. This result is not compatible with Bells assumption that spin 1/2 particles are deected in a Stern-Gerlach device. Assuming a more realistic Hamiltonian Hz + Hx including a gradient in x direction the total Iz is not conserved and fully entanglement is not expected in this case. The conclusion is that Bells theorem is not applicable to spin coincidence measurement originally discussed by Bell.

Place, publisher, year, edition, pages
2019. Vol. 10, no 10, p. 1247-1254
Keywords [en]
Bells Theorem, Disentanglement, Stern-Gerlach Coincident Measurement, Singlet Spin State
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:umu:diva-164094DOI: 10.4236/jmp.2019.1010083OAI: oai:DiVA.org:umu-164094DiVA, id: diva2:1360654
Funder
Swedish Research CouncilAvailable from: 2019-10-14 Created: 2019-10-14 Last updated: 2019-11-05Bibliographically approved

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Westlund, Per-Olof
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