Introductory Chapter: Panorama of Contemporary Quantum Mechanics - Concepts and Applications

1. Introduction

Quantum mechanics has been around for more than a century. Since its birth at the beginning of the twentieth century, it has undergone a tremendous growth. But, it is only now that quantum mechanics has emerged in our daily life. This is just a normal evolution for any branch of physics. Take for example, the electromagnetic theory. It came into existence with the stunning work of James Clerk Maxwell in 1865 [1], which predicted the existence of radio waves, and this has led to the tremendous development of electronics throughout the twentieth century in the fields of communication, detection, and transmission of information and data.

Quantum mechanics is the physics of subatomic phenomena, which has remained a mysterious domain for a long time. Its laws have bewildered many because they are quite counter-intuitive. Its development has started with the very concept of “quantization,” which entails the absorption as well as the emission of energy in discrete amounts and not continuous as it is usually perceived in classical physics. This milestone principle, established by Max Planck toward the end of the nineteenth century, has started a golden age of discoveries during almost three decades.

2. The present role of quantum mechanics in technologies

Since then, quantum principles have been at the foundations of our day-to-day technologies, such as the transistor, computer chip, LASER, GPS, NMR imaging system, LED lamps, solar cells, etc. to name a few. The working of transistors is based simultaneously on the quantum description of matter, namely, the wave-particle duality and the Heisenberg uncertainty principle, which is inherent to quantum evolution equations. In recent years, with the appearance of Big data, massive exchange of information, and the ensuing cryptography challenges, it becomes necessary to turn to quantum engineering to find a way out to manage these problems. A full array of “quantum” technologies has been initiated since the seminal paper of R. P. Feynman “Simulating Physics with Computers” [2], in which the notion of quantum computer was introduced as it is built on new quantum engineering (quantum electronics/spintronics).

There is no doubt that quantum principles are here to stay and will continue to be at the origin of new technological innovations in coming years. This book is intended to give a first glimpse on a few topics of this fascinating development perspective on the future of the real world and to stimulate research in order to meet the futures challenges. Most urgent is the investigation into the quantum behavior of large systems such as populations of photons or atoms in the regime of Bose condensates in which unexpected properties may arise. In particular, some macroscopic effects may be explained from microscopic levels, thanks to quantum mechanics which governs the evolution rules at the atomic level.

One of the most salient features of modern physics is the inherent existence of hidden symmetry in nature. The discovery of such symmetries is often very fruitful in the sense that it leads to further discoveries and predictions. Strangely enough, even symmetry breaking can also be a source of new phenomena occurrence. This is why since decades, one has sought to make quantum mechanics supersymmetric and the pursuit of supersymmetry in elementary particles is still ongoing these days in large particle accelerators.

Finally, it should be mentioned that quantum mechanics has ushered mankind into the area of fictional reality with the search for the realization and exploitation of the quantum concept of entanglement. In 1935, analyzing the possible outcome of a Gedankenexperiment following the rules of quantum mechanics by Einstein, Podolski, and Rosen has arrived at a paradoxical conclusion, known for a long time as the EPR Paradox [3]. This is because one can predict the value of a dynamical quantity of a system, which has classically nothing to do with a companion system on which measurements are performed. Quantum mechanics coins these systems as “entangled.” Nowadays, quantum entanglement has been experimentally demonstrated and considered to be the main ingredient in the working of a quantum computer.

As computing is an exponentially growing activity in science and technology as well as in economics, finance, and management, “classical” computers have reached their limits as far as performance and costs are concerned. Quantum computers which are based on totally new quantum concepts (superposition and entanglement) with their revolutionary capacity for data storage and speed of calculation seem to be the ideal solution to the previous problem. Basic logic gates and circuits are cast and discussed in the language of the so-called quantum bits or q-bits (instead of classical bits) which are their building blocks. They open the way to mastering cyber security in data transfer, Big data mining, and the like.

Thus, our future appeared to be structured by quantum principles via quantum technology and engineering, and this book offers a view of what might be the coming reality we will have to deal with.