Quantum Computers First Steps Towards a Realization

University of Innsbruck, Austria and University of Oxford, England. 

The idea of building faster computers by exploiting the counterintuitive features of quantum mechanics was conceived more than a decade ago (Feynman 1982). However, the field remained a purely theoretical one until only recently. No experimental physicist would seriously have considered to set up an experiment to realizing a quantum computer (QC) in his/her lab. During the last few years, however, the situation has changed due to some seminal experimental and theoretical developments. The purpose of this chapter is to review important recent results which have nourished the hope that QCs might become feasible technology. 

Non-Standard Computation. T. GramQ, S. Bomholdt, M. GroB, M. Mitchell, T. Pellizzari Copyright 1998 WILEY-VCH Verlag GmbH, Weinheim ISBN 3-527-29427-9 

6 Quantum Computers First Steps Towards a Realization 

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The time evolution of such a system is described by a 2 °x2 °matrix This demonstrates the complexity of quantum mechanical time evolution. At the same time it becomes clear that quantum systems have - due to the fact that they describe the evolution of all possible states simultaneously - a sort of inner parallelism . Therefore, they will be an ideal medium for real parallel computations as soon as the dynamical behaviour of the quantum states can be controlled in isolation from the rest of the world (with which an interaction is only needed if one wants to read out the result). New experimental possibilities for realizing quantum computers, ranging from neutral atoms interacting with microwaves over optical cavities and nuclear spins to trapped ions, offer most promising perspectives [15]. The chapters by Tino Gramss and Thomas Pellizzari on the Theory of Quantum Computation and First Steps Towards a Realization of Quantum Computers, respectively, will introduce the reader to recent developments in this exciting field. 

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