Introduction

Abstract

The physical systems realizing quantum objects range from trapped individual atoms to solid-state devices. All of them possess their pros and cons, in the development of quantum technologies. It is not too much to say that such characteristics of quantum systems result from their surrounding environment, as it is apparent in their operating frequency and coherence time. In this introductory chapter, the authors try to set readers’ minds on quantum technologies by presenting a few valuable ideas about its history, notions of various individual and hybrid quantum systems, and the relationship between quantum-bit energies and the temperature of the surrounding environment.