Quantum chemistry is the use of quantum mechanics to model molecules and their dynamics. In this article we will seek to understand quantum chemical practice via the lens of `de-idealization' based upon a selection of examples together with a more general survey of relevant scientific literature. We will offer some general remarks regarding the problem of modelling molecules and the different approach quantum chemists have developed. We will then consider features of two particular models relating to diatomic molecules and environmental interaction before returning to a more general discussion of the different dimensions of de-idealization relevant to quantum chemistry. Our discussion will support the general claim of continuity between the various families of models in quantum chemistry show and other areas of quantum matter modelling and of the commonness of de-idealization approach under which a model can be modified to be more realistic model in the sense of empirical adequacy without necessarily involving constructing representations that are more veridical.
Quantum chemistry is the use of quantum mechanics to model molecules and their dynamics. In this article we will seek to understand quantum chemical practice via the lens of `de-idealization' based upon a selection of examples together with a more general survey of relevant scientific literature. We will offer some general remarks regarding the problem of modelling molecules and the different approach quantum chemists have developed. We will then consider features of two particular models relating to diatomic molecules and environmental interaction before returning to a more general discussion of the different dimensions of de-idealization relevant to quantum chemistry. Our discussion will support the general claim of continuity between the various families of models in quantum chemistry show and other areas of quantum matter modelling and of the commonness of de-idealization approach under which a model can be modified to be more realistic model in the sense of empirical adequacy without necessarily involving constructing representations that are more veridical.
This introductory chapter provides an overview of quantum mechanics, which is a subject of central importance in chemistry, and is by nature a mathematical theory. The chemist's approach to the understanding of matter and its chemical transformations is to take a microscopic view, connecting experimental observation with the properties of constituent molecules. However, at the microscopic level, atoms, molecules, and their constituent particles do not obey the familiar laws of mechanics that pertain to the everyday macroscopic world. For example, the existence of molecular line spectra indicates that molecules can be found only at certain well-defined energies, unlike objects at our own scale whose energy appears to be continuously variable. This book aims to explain the fundamentals of quantum mechanics from the point of view of chemistry; describe the areas of chemistry where quantum mechanics is most important; and show how quantum mechanics is applied to chemical problems.
Practical challenges in simulating quantum systems on classical computers have been widely recognized in the quantum physics and quantum chemistry communities over the past century. Although many approximation methods have been introduced, the complexity of quantum mechanics remains hard to appease. The advent of quantum computation brings new pathways to navigate this challenging and complex landscape. By manipulating quantum states of matter and taking advantage of their unique features such as superposition and entanglement, quantum computers promise to efficiently deliver accurate results for many important problems in quantum chemistry, such as the electronic structure of molecules. In the past two decades, significant advances have been made in developing algorithms and physical hardware for quantum computing, heralding a revolution in simulation of quantum systems. This Review provides an overview of the algorithms and results that are relevant for quantum chemistry. The intended audience is both quantum chemists who seek to learn more about quantum computing and quantum computing researchers who would like to explore applications in quantum chemistry.
The field of quantum chemistry is concerned with the modelling and simulation of the behaviour of molecular systems on the basis of the fundamental equations of quantum mechanics. Since these equations exhibit an extreme case of the curse of dimensionality (the Schrödinger equation for N electrons being a partial differential equation on \mathbb R^{3N} ), the quantum-chemical simulation of even moderate-size molecules already requires highly sophisticated model-reduction, approximation, and simulation techniques. The workshop brought together selected quantum chemists and physicists, and the growing community of mathematicians working in the area, to report and discuss recent advances on topics such as coupled-cluster theory, direct approximation schemes in full configuration-interaction (FCI) theory, interacting Green’s functions, foundations and computational aspects of density-functional theory (DFT), low-rank tensor methods, quantum chemistry in the presence of a strong magnetic field, and multiscale coupling of quantum simulations.
Abstract Philosophers have claimed that: (a) Born–Oppenheimer approximation methods for solving molecular Schrödinger equations violate the Heisenberg uncertainty relations; therefore, (b) ‘quantum chemistry’ is not fully quantum; and (c) therefore chemistry does not reduce to physics. This paper analyses the reasoning behind Born–Oppenheimer methods and shows that they are internally consistent and fully quantum mechanical, contrary to (a)–(c). Our analysis addresses important issues of mathematical rigour, physical idealization, reduction, and classicality in the quantum theory of molecules, and we propose an agenda for the philosophy of quantum chemistry more grounded in scientific practice.
Quantum Mechanics 2 opens by stating that the chemist's approach to the understanding of matter and its chemical transformations is to take a microscopic view, connecting experimental observation with the properties of the constituent molecules. Atoms and sub-atomic particles do not obey the classical laws of mechanics but conform rather to the laws of quantum mechanics. Quantum mechanics is thus of central importance in chemistry. In order to understand the behaviour of molecules and their constituent particles it is necessary to have a thorough grounding in the principles and applications of quantum mechanics. This text provides a toolkit for applying quantum mechanics to chemical problems, introducing more advanced approaches using approximate methods. It describes areas of chemistry where quantum mechanics is important, and shows how quantum mechanics can be applied to chemical problems.
Abstract The rapid and successful strides in quantum chemistry in the past decades can be largely credited to a conspicuous synergy between theoretical and computational advancements. However, the architectural computer archetype that enabled such a progress is approaching a state of more stagnant development. One of the most promising technological avenues for the continuing progress of quantum chemistry is the emerging quantum computing paradigm. This revolutionary proposal comes with several challenges, which span a wide array of disciplines. In chemistry, it implies, among other things, a need to reformulate some of its long established cornerstones in order to adjust to the operational demands and constraints of quantum computers. Due to its relatively recent emergence, much of quantum computing may still seem fairly nebulous and largely unknown to most chemists. It is in this context that here we review and illustrate the basic aspects of quantum information and their relation to quantum computing insofar as enabling simulations of quantum chemistry. We consider some of the most relevant developments in light of these aspects and discuss the current landscape when of relevance to quantum chemical simulations in quantum computers.