Neutron-scattering experiments and quantum entanglement

R. Moreh

Hidehiko Sugimoto, Aiko Okumura, 寛之 結城

We calculate the scattering function of neutrons, $S(\stackrel{P\vec}{q},\ensuremath{\omega})$, from a pair of nuclei in entangled states caused by the quantum-mechanical indistinguishability of particles. From the calculation, the conditions for detecting the entanglement of protons in solids by neutron scattering experiments are clarified. Our conclusion is that the entangled state of a proton pair, if it exists, can be observed by performing neutron scattering experiments at very low temperatures for elastic scattering and with high energy resolution for inelastic scattering.

F.J. Duarte

E. Karlsson, Stephen William Lovesey

Allegations that our theoretical description of neutron scattering by entangled spin and spatial degrees of freedom is incorrect are shown to be misplaced for the allegations are derived from a naively incomplete, quantum mechanical calculation of neutron scattering by identical nuclei.

F. J. Duarte

Roger Arthur Cowley

It is shown that quantum entanglement in condensed matter can be observed with scattering experiments if the energy resolution of the experiments enables a clear separation between the elastic scattering and the scattering from the excitations in the system. These conditions are not satisfied in recent deep inelastic neutron scattering experiments from hydrogen-containing systems that have been interpreted as showing the existence of quantum entanglement for short times in, for example, water at room temperature. It is shown that the theory put forward to explain these experiments is inconsistent with the first-moment sum rule for the Van Hove scattering function and we suggest that the theory is incorrect. The experiments were performed using the unique EVS spectrometer at ISIS and suggestions are made about how the data and their interpretation should be re-examined.