We report on neutron-proton Compton scattering experiments on various hydrogen containing materials like water, an organic polymer and an ionic metal hydride. Furthermore, results of an electron-proton Compton scattering experiment on the polymer are presented. The results reveal a strong decrease of the scattering integral intensities due to the protons in these materials. Thus far these effects have found no common explanation based on existing condensed matter theories. Rather, they invoke the existence of quantum correlations (also called quantum entanglement-QE) and decoherence between the particles. Of particular importance in the present context is the fact that the interaction time of the probe (i.e. neutron or electron) must be of the same order of magnitude as the decay of the coherence (also called decoherence) of the correlated particles. The found experimental effects and their possible explanations may have far reaching consequences for condensed matter physics and in particular for the theoretical treatment of hydrogen containing materials. (c) 2005 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.