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arXiv:0804.4759

Design and control of dynamical quantum processes in ortho para H2 conversion on surfaces

Rifki Muhida, Riza Muhida, Wilson Agerico Diño, Hiroshi Nakanishi, Hideaki Kasai

Published Apr 30, 2008• 0 citations
arXivHTMLPDF

Abstract

We present here a novel, cost-effective method for increasing and controlling the ortho para H2 (o p H2) conversion yield. First, we invoke two processes derived from fundamental, surface science insights, based on the effect of molecular orientation on the hydrogen solid surface reaction, i.e., dynamical quantum filtering and steering, and apply them to enhance the o p H2 conversion yield. Second, we find an important factor that can significantly influence the yield i.e., inhomogeneity of spin density distribution. This factor gives us a promising possibility to increase the yield and to find the best catalyst e.g., design of materials that can function as catalysts for the o p H2 conversion.

DOI
10.48550/arxiv.0804.4759

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We present here a novel, cost-effective method for increasing and controlling the ortho para H2 (o p H2) conversion yield. First, we invoke two processes derived from fundamental, surface science insights, based on the effect of molecular orientation on the hydrogen solid surface reaction, i.e., dynamical quantum filtering and steering, and apply them to enhance the o p H2 conversion yield. Second, we find an important factor that can significantly influence the yield i.e., inhomogeneity of spin density distribution. This factor gives us a promising possibility to increase the yield and to find the best catalyst e.g., design of materials that can function as catalysts for the o p H2 conversion.
Abstract When hydrogen molecules collide with a surface, they can either scatter away from the surface or undergo a dissociation reaction leaving two hydrogen atoms adsorbed on the surface. The relative probabilities of these two potential outcomes could depend on the rotational orientation of the impinging molecules, however, due to the lack of steric control techniques for ground state hydrogen, direct measurements of this dependency were previously inaccessible to experiments. Here, we demonstrate that magnetic field manipulation can be used to control the rotational orientation of the impinging H2 and change the balance between reactive and scattering collision events. Analysing the controlled collision experiments reveals that molecules approaching the surface in a helicopter orientation have a higher probability to react and dissociate, whereas those which approach in a cartwheel orientation are more likely to scatter.
Abstract Hydrogen has emerged as a promising energy source, holding the key to achieve low-carbon and sustainable mobility. However, its applications are still limited by modest conversion efficiency in the electrocatalytic oxygen reduction reaction (ORR) within fuel cells. Consequently, the development of novel catalysts and a profound understanding of the underlying reactions have become of paramount importance. The complex nature of the ORR potential energy landscape and the presence of strong electronic correlations present challenges to atomistic modelling using classical computers. This scenario opens new avenues for the implementation of novel quantum computing workflows to address these molecular systems. Here, we present a pioneering study that combines classical and quantum computational approaches to investigate the ORR on pure platinum and platinum/cobalt surfaces. Our research demonstrates, for the first time, the feasibility of implementing this workflow on the H1-series trapped-ion quantum computer and identify the challenges of the quantum chemistry modelling of this reaction. The results highlight the involvement of strongly correlated species in the cobalt-containing catalyst, suggesting their potential as ideal candidates for showcasing quantum advantage in future applications.
We evaluate a population of ortho nuclear spin states in H2 gas in the 22-pole linear radio-frequency trap using N + ions as a chemical probe. The rate coecient of the reaction N + + H2 ! NH + + H strongly depends on the nuclear spin states of the H2 molecules at the temperature 11 K. To achieve astrophysically relevant conditions in other our experiments, we convert the normal H2 gas (25% of the molecules in para-states) to H2 gas with a distribution of the nuclear spin states corresponding to the temperatures in prestellar cores (> 99 % in para-states at temperatures 20 K) by a catalytic converter (para-hydrogen generator). Tests by the aforementioned probing reaction show that the abundance of ortho-H2 in such H2 gas is (0:5 0:2)% in the trap. Para-to-ortho back-conversion of H2 gas in the generator's outlet tube was studied and its rate was estimated to lie in the interval (10 4 ; 10 2 )s 1 .
Solid-state nuclear magnetic resonance (NMR) has emerged as an important technique for material characterization, finding extensive applications across a diverse range of disciplines including physics, materials science, chemistry, and biology. Its utility stems from the ability to probe the local atomic environments and molecular dynamics within solid materials, which provides information on the composition of the material. In recent years, the scope of solid-state NMR has expanded into the realm of quantum information science and technology, where its abundant many-body interactions pulse control methodologies make it have significant research value and application potential. This paper offers a comprehensive overview of the research objects and theoretical underpinnings of solid-state NMR, delving into the critical nuclear spin interaction mechanisms and their corresponding Hamiltonian forms. These interactions, which include dipolar coupling, chemical shift anisotropy, and quadrupolar interactions, are fundamental to the interpretation of NMR spectra and the understanding of material properties at the atomic level. Moreover, the paper introduces typical dynamical control methods employed in the manipulation of solid-state nuclear spins. Techniques such as dynamical decoupling, which mitigates the effects of spin-spin interactions to extend coherence times, and magic-angle spinning, which averages out anisotropic interactions to yield high-resolution spectra. These methods are essential for enhancing the sensitivity and resolution of NMR experiments, enabling the extraction of detailed structural and dynamic information from complex materials. Then we introduce some recent advancements in quantum control based on solid-state NMR, such as nuclear spin polarization enhancement techniques, which include dynamic nuclear polarization (DNP) and cross polarization (CP), significantly boost the sensitivity of NMR measurements. Additionally, the control techniques of Floquet average Hamiltonians are mentioned, showcasing their role in the precise manipulation of quantum states and the realization of quantum dynamics. Finally, the paper presents a series of seminal research works that illustrate the application of solid-state NMR quantum control technologies in the field of quantum simulation. These studies demonstrate how solid-state NMR can be leveraged to simulate and investigate quantum many-body systems, providing valuable insights into quantum phase transitions, entanglement dynamics, and other phenomena relevant to quantum information science. By bridging the gap between fundamental research and practical applications, solid-state NMR continues to play a crucial role in advancing our understanding of quantum materials and technologies.
The molecular energies of chemical systems have been successfully calculated on quantum computers, however, more attention has been paid to the dynamic process of chemical reactions in practical application, especially in catalyst design, material synthesis. Due to the limited the capabilities of the noisy intermediate scale quantum (NISQ) devices, directly simulating the reaction dynamics and determining reaction pathway still remain a challenge. Here we develop the ab initio molecular dynamics based on quantum computing to simulate reaction dynamics by extending correlated sampling approach. And, we use this approach to calculate Hessian matrix and evaluate computation resources. We test the performance of our approach by simulating hydrogen exchange reaction and bimolecular nucleophilic substitution SN2 reaction. Our results suggest that it is reliable to characterize the molecular structure, property, and reactivity, which is another important expansion of the application of quantum computing
The quantum computation of electronic energies can break the curse of dimensionality that plagues manyparticle quantum mechanics.It is for this reason that a universal quantum computer has the potential to fundamentally change computational chemistry and materials science, areas in which strong electron correlations present severe hurdles for traditional electronic structure methods.Here we present a state-of-the-art analysis of accurate energy measurements on a quantum computer for computational catalysis, using improved quantum algorithms with more than an order of magnitude improvement over the best previous algorithms.As a prototypical example of local catalytic chemical reactivity we consider the case of a ruthenium catalyst that can bind, activate, and transform carbon dioxide to the high-value chemical methanol.We aim at accurate resource estimates for the quantum computing steps required for assessing the electronic energy of key intermediates and transition states of its catalytic cycle.In particular, we present quantum algorithms for double-factorized representations of the four-index integrals that can significantly reduce the computational cost over previous algorithms, and we discuss the challenges of increasing active space sizes to accurately deal with dynamical correlations.We address the requirements for future quantum hardware in order to make a universal quantum computer a successful and reliable tool for quantum computing enhanced computational materials science and chemistry, and identify open questions for further research.