Discriminating quantum gravity models by gravitational decoherence

Several phenomenological approaches to quantum gravity assume the existence of a minimal measurable length and/or a maximum measurable momentum near the Planck scale. When embedded into the framework of quantum mechanics, such constraints induce a modification of the canonical commutation relations and thus a generalization of the Heisenberg uncertainty relations, commonly referred to as generalized uncertainty principle (GUP). Different models of quantum gravity imply different forms of the GUP. For instance, in the framework of string theory the GUP is quadratic in the momentum operator, while in the context of doubly special relativity it includes an additional linear dependence. Among the possible physical consequences, it was recently shown that the quadratic GUP induces a universal decoherence mechanism, provided one assumes a foamy structure of quantum spacetime close to the Planck length. Along this line, in the present work we investigate the gravitational decoherence associated to the linear-quadratic GUP and we compare it with the one associated to the quadratic GUP. We find that, despite their similarities, the two generalizations of the Heisenberg uncertainty principle yield decoherence times that are completely uncorrelated and significantly distinct. Motivated by this result, we introduce a theoretical and experimental scheme based on cavity optomechanics to measure the different time evolution of nonlocal quantum correlations corresponding to the two aforementioned decoherence mechanisms. We find that the deviation between the two predictions occurs on time scales that are macroscopic and thus potentially amenable to experimental verification. This scenario provides a possible setting to discriminate between different forms of the GUP and therefore different models of quantum gravity.Comment: v1: 11 pages, 2 figures; v2: 11 pages, 2 figures, title, abstract and references slightly edited and updated for better clarity; no change in the physics; v3: 14 pages, 3 figures, title changed, new section and clarifications adde

Chemical Vapour Deposition of Graphene—Synthesis, Characterisation, and Applications: A Review

Graphene as the 2D material with extraordinary properties has attracted the interest of research communities to master the synthesis of this remarkable material at a large scale without sacrificing the quality. Although Top-Down and Bottom-Up approaches produce graphene of different quality, chemical vapour deposition (CVD) stands as the most promising technique. This review details the leading CVD methods for graphene growth, including hot-wall, cold-wall and plasma-enhanced CVD. The role of process conditions and growth substrates on the nucleation and growth of graphene film are thoroughly discussed. The essential characterisation techniques in the study of CVD-grown graphene are reported, highlighting the characteristics of a sample which can be extracted from those techniques. This review also offers a brief overview of the applications to which CVD-grown graphene is well-suited, drawing particular attention to its potential in the sectors of energy and electronic devices

Effect of LaNi3 Amorphous Alloy Nanopowders on the Performance and Hydrogen Storage Properties of MgH2

Due to its affordable price, abundance, high storage capacity, low recycling coast, and easy processing, Mg metal is considered as a promising hydrogen storage material. However, the poor de/rehydrogenation kinetics and strong stability of MgH2 must be improved before proposing this material for applications. Doping MgH2 powders with one or more catalytic agents is one common approach leading to obvious improving on the behavior of MgH2. The present study was undertaken to investigate the effect of doping MgH2 with 7 wt% of amorphous(a)-LaNi3 nanopowders on hydrogenation/dehydrogenation behavior of the metal hydride powders. The results have shown that rod milling MgH2 with a-LaNi3 abrasive nanopowders led to disintegrate microscale-MgH2 powders to nanolevel. The final nanocomposite product obtained after 50 h–100 h of rod milling revealed superior hydrogenation kinetics, indexed by short time (8 min) required to absorb 6 wt% of H2 at 200 °C/10 bar. At 225 °C/200 mbar, nanocomposite powders revealed outstanding dehydrogenation kinetics, characterized by very short time (2 min) needed to release 6 wt% of H2. This new tailored solid-hydrogen storage system experienced long cycle-life-time (2000 h) at 225 °C without obeying to sever degradation on its kinetics and/or storage capacity