Quantum Computation: Models

Documentation "

" explains how quantum computation works under the assumption that elementary quantum logic gates are available. But how can one build a quantum computer, a machine, that allows such quantum logic gates? Quantum computers are physical systems and the implementation of all quantum logic gates is governed by the laws of physics. In this documentation, we discuss the basic physical principles that are directly involved in the implementation of quantum logic gates. Through the course of the discussion, we will find some basic conditions and requirements that one has to fulfill to build a quantum computer.
By now, there are many quantum computer architectures that have not only been proposed and tested at the research level but are also actually running. However, understanding each architecture requires a certain level of knowledge regarding the physical systems. For example, to understand a quantum computer based on superconducting circuits, one has to first understand the superconductivity, Josephson effect, flux quantization, Josephson inductance, and the interaction of superconducting circuits with electromagnetic fields. Such discussions often hinder access to the essential part of the operating principle of a quantum computer, and are beyond the scope of this documentation.
Here, we consider an idealistic and minimal quantum system that is suitable for quantum computation, and we discuss how to control it to implement the desired quantum logic gates. It is certainly impractical, yet it will highlight the key requirements when one wants to actually develop a quantum computer based on practical devices. Through the discussions, we will indicate how the relevant parts are related to actual quantum computer architectures.

See also Chapter 3 of the