Journal of Alloys and Compounds 404–406 (2005) 787–789 Short lived protonic quantum entanglement and coupling to the electronic environment in LaH 2 and LaH 3 T. Abdul-Redah a,b, ∗ , P. Georgiev c , D.K. Ross c , M. Krzystyniak d , C.A. Chatzidimitriou-Dreismann d a School of Physical Sciences, The University, CT2 7NR, Canterbury, UK b ISIS Facility, Rutherford Appleton Laboratory, Chilton/Didcot, OX11 0QX, UK c Maxwell Building, University of Salford, Salford, M5 4WT, UK d Institute of Chemistry, Stranski Lab. ER1, TU Berlin, D-10623 Berlin, Germany Received 7 June 2004 Available online 14 July 2005 Abstract Very recently, a temperature dependent decrease of the protonic neutron scattering cross section σ H in LiH using neutron Compton scattering (NCS) has been reported. The decrease of σ H – which has been found in various materials using different experimental methods – is attributed to short-lived protonic quantum entanglement and it was suggested that the novel temperature dependence is due to the different coupling of the protons to the environment. The exact mechanism of the loss of coherence (i.e. decoherence) of the protonic quantum entangled states due to the interaction with the environment in condensed matter is not fully understood yet. To shed more light onto that, the NCS of LaH 2 and LaH 3 has been measured. While LaH 2 is metallic, LaH 3 is an isolator, thus providing completely different electronic environments the protons are coupled to. The experiment shows that σ H is smaller for LaH 3 than it is for LaH 2 . This result strongly suggest that the different couplings of the protons to the different electronic environments lead to different anomalies. © 2005 Elsevier B.V. All rights reserved. Keywords: Hydrogen storage materials; Quantum effects; Neutron Compton scattering; Attosecond physics 1. Introduction The importance of hydrogen in materials in general and in metals in particular for technological applications and in nat- ural sciences is beyond any dispute. The increased awareness of the limitation of the natural fossil fuel reserves triggered a rethinking in new directions about energy generation. The increasing demand on the features of new materials necessi- tates the application of new production processes as well as new fundamental research towards a better understanding of the physical and chemical properties of hydrogen containing materials. In condensed phases interactions of a particle with its en- vironment can lead to quantum entanglement (QE). Such ef- fects are theoretically expected to be extremely short-lived, ∗ Corresponding author. Tel.: +44 1235 445718/445720. E-mail address: t.abdul-redah@rl.ac.uk (T. Abdul-Redah). due to environmental disturbances. Therefore, it has been widely believed that they cannot be experimentally detected. However, based on previous theoretical work [1], the detec- tion of protonic QE in condensed systems using sufficiently “fast” scattering techniques was proposed. Particularly suit- able for this purpose is the neutron Compton scattering (NCS) method the time scale of which lying in the sub-femtosecond range. In recent years we reported on a new fundamental aspect of the quantum dynamics of hydrogen in various condensed systems like water [2], organic compounds [3–6], and inter- stitial [7–9] as well as ionic metal hydrides [10]. The nov- elty of our results lies in the fact that the protons show an effective number density being different from the one sup- posed to be according to sample preparation. Thus, far these effects have not found a common explanation based on exist- ing condensed matter theories. Rather, these anomalies are at- tributed to the existence of short-lived quantum entanglement 0925-8388/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2005.05.004