Quantum computers nuclear magnetic resonance computing

In most fields of physical chemistry, the use of digital computers is considered indispensable. Many things are done today that would be impossible without modem computers. These include Hartree-Fock ab initio quantum mechanical calculations, least-squares refinement of x-ray crystal stmctures with hundreds of adjustable parameters and mar r thousands of observational equations, and Monte Carlo calculations of statistical mechanics, to mention only a few. Moreover computers are now commonly used to control commercial instalments such as Fourier transform infrared (FTIR) and nuclear magnetic resonance (FT-NMR) spectrometers, mass spectrometers, and x-ray single-crystal diffractometers, as well as to control specialized devices that are part of an independently designed experimental apparatus. In this role a computer may give all necessary instaic-tions to the apparatus and record and process the experimental data produced, with relatively little human intervention. 

R291 H. K. Cummings and J. A. Jones, Nuclear Magnetic Resonance A Quantum Technology for Computation and Spectroscopy , Contemp. Phys., 2000, 41, 383... 

Quantum computational methods are mainly used in systems for which electronic properties are of interest, such as molecular orbitals. Nuclear Magnetic Resonance (NMR) spectra, and polarizability. Usually an optimization process is carried out [3]. It consists in finding the structure which exhibits the lowest energy. The prerequisite in manipulating approximations to solve the Schrodinger equation gives rise to different approaches. They can be roughly classified into three major types ab initio (Hartree-Fock method and derivatives), density functional theory (DFT), and semiempirical methods, ab initio is a Latin locution which means from the... 

J.A. Jones, M. Mosca, Implementation of a quantum algorithm on a nuclear magnetic resonance quantum computer, J. Chem. Phys. 109 (1998) 1648. 

M.S. Anwar, D. Blazina, H.A. Carteret, S.B. Duckett, T.K. Halstead, J.A. Jones, C.M. Kozak, R.J.K. Taylor, Preparing highly pure initial states for nuclear magnetic resonance quantum computing, Phys. Rev. Lett. 93 (2004) 040501-1. 

However interesting may be, QC and QIP would be restricted to a bunch of mathematical results if there was no way to implement them in the physical world, as much as a Turing Machine (see below) would be a mere theoretical curiosity without the existence of computers This book deals with a particular way to implement QC and QIP it is called Nuclear Magnetic Resonance, or simply NMR. There are excellent books in the subjects of quantum computation and quantum information [6,7], in NMR [8] and in (classical) computation [9]. This book exploits elements of these three different fields, and put them together in order we can understand NMR-QIP. In this chapter we will introduce the basic elements of computation, and will discuss the physics of computational processes. Chapters 2 and 3 introduce the necessary background of NMR and quantum computation theories, in order we can exploit the realizations of NMR-QIP in the subsequent chapters. 

L.M.K. Vandersypen, C.S. Yannoni, I.L. Chuang, Liquid state NMR quantum computing, in D.M. Grant, R.K. Harris (Eds.), Encyclopedia of Nuclear Magnetic Resonance (John Wiley Sons, Chichester, 2002), pp. 687-397. 

I.L. Chuang, N. Gershenfeld, M.G. Kubinec, D.W. Leung, Bulk quantum computation with nuclear magnetic resonance theory and experiment, Proc. R. Soc. Lond. A 457 (1998) 447-467. 

J.A. Jones, V. Vedral, A. Ekert, G. CastagnoU, Geometric quantum computation using nuclear magnetic resonance. Nature 403 (2000) 869. 

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