Attosecond protonic quantum entanglement in collision experiments with neutrons and electrons

Several neutron Compton scattering (NCS) experiments on liquid and solid samples containing protons or deuterons show a striking anomaly, namely, a shortfall in the intensity of energetic neutrons scattered by the protons; e.g., neutrons colliding with water for just 50-500 attoseconds (as) will see a ratio of hydrogen to oxygen of roughly 1.5 to 1, instead of the 2 to 1 ratio corresponding to the chemical formula H2O. Due to the large energy and momentum transfers applied, the duration of a neutron-proton scattering event (the so-called scattering time) is a fraction of a femtosecond, which is extremely short compared to condensed matter relaxation times. Very recently, this new effect was independently confirmed by electron-proton Compton scattering (ECS) from a solid polymer. The similarity of the ECS and NCS results is striking, because the two projectiles interact with protons via fundamentally different forces, namely, the electromagnetic and strong forces. Theoretical considerations suggest the presence of attosecond entanglement, in which the quantum dynamics of the scattering protons and the surrounding particles are all connected; this in turn changes the nature of the scattering results. The scattering times of NCS and ECS are similar to the characteristic time of "electron motion," so that the Born-Oppenheimer approximation is not applicable here. The results and their interpretation provide novel insights into dynamical processes (e.g., the onset of elementary chemical reactions) in molecules and condensed matter at the attosecond scale.