Abstract – Armin Danner

April 11, 2019 1:28 pm Published by

Spin-Rotation Coupling Observed in Neutron Interferometry

Spin-rotation coupling is an extension of the Sagnac effect, based upon the inertia of intrinsic spin. Its existence was predicted and neutron interferometric experiments to verify it were proposed [1,2]. The latter suggestion was to induce a coupling between the spin and the rotation of a magnetic field. The results of a previous neutron polarimeter experiment are in accordance with the prediction of spin-rotation coupling but can also be explained with the semi-classical Bloch equations.

The technical requirements to conduct a corresponding neutron interferometer experiment are elaborate. As the coupling is small, the required phase stability of interferograms is critical. A spin manipulator is developed [3] which produces a rotating magnetic field while ensuring a non-adiabatic field transition necessary to induce Larmor precession. This is achieved using a geometry without material in the neutron beam to prevent dephasing.

A neutron interferometer experiment is conducted to test for spin rotation coupling [4]. As predicted, the observed phase of the interferograms is linearly dependent on the frequency of the rotating magnetic field. This result is only predicted in quantum mechanics.


  1. B. Mashhoon, Neutron interferometry in a rotating frame of reference, Phys. Rev. Lett. 61, 2639 (1988).
  2. B. Mashhoon and H. Kaiser, Inertia of intrinsic spin, Physica B 385–386, 1381 (2006).
  3. A. Danner et al., Development and perfomance of a miniaturised spin rotator suitable for neutron  interferometer experimentsJ. Phys. Commun. 3, 035001 (2019).
  4. A. Danner et al., Spin-Rotation Coupling Observed in Neutron Interferometry, arXiv 1904.07085 (2019).