Entangled Neutron Beams: A possible new avenue to exploring Quantum Materials

We have recently demonstrated that the Larmor instrument at ISIS can be used to construct two and three-fold entangled states in a neutron beam [1]. Entanglement among the spin, energy, and trajectory degrees of freedom for neutrons was indicated by observing clear violations of both the Clauser-Horne-Shimony-Holt and Mermin contextuality inequalities in the same experimental setup. Moreover, the entanglement length associated with this experiment was 1 micron (as opposed to the cm length scales previously seen with neutron interferometer experiments [2]), and could be experimentally varied from several nm to several microns. We suggest that such a beam, with an experimentally controllable microscopic length scale, may represent a fundamentally new probe of correlated matter. Experiments are planned to demonstrate these methods to probe entanglement in quantum spin chains.

[1] J. Shen et al., arXiv:1908.09823
[2] Hasegawa et al., Phys. Rev. A 81, 032121 (2010).