Quantumness of correlations and Maxwell's demon in molecular excitations created by neutron scattering

Abstract

Modern neutron scattering instruments provide a "two-dimensional spectroscopy", measuring not only the energy of a molecular excitation but also the momentum transfer causing the excitation. Experiments with H2O (ice, single molecules) and other systems reveal a thus far unknown quantum-correlation property involving the molecule's environment. Applying quantum-information concepts, like 'discord' and 'Maxwell's demon', a striking "anomalous" Q-E-spectral position of several excitations is qualitatively explained. Nonclassical correlations known as entanglement, quantum discord, quantum deficit, measurement-induced disturbance, quantum Maxwell's demon, etc., may provide novel insights into quantum-information processing, quantum-thermodynamics processes, open-system dynamics, quantum molecular dynamics, and general quantum chemistry. We study a new effect of quantumness of correlations accompanying collision of two distinguishable quantum systems A and B, the latter being part of a larger (interacting) system B-+-D. In contrast to the common assumption of a classical environment or "demon" D, the quantum case exhibits striking new qualitative features. Here, in the context of incoherent inelastic neutron scattering from H-atoms which create molecular excitations (vibration, rotation, translation), we report theoretical and experimental evidence of a new phenomenon: a considerably reduced effective mass of H, or equivalently, an anomalous momentum-transfer deficit in the neutron-H collision. These findings contradict conventional theoretical expectations even qualitatively, but find a straightforward interpretation in the new theoretical frame under consideration.