Fuelled by the invention of the transistor, integrated circuit, laser and optical fiber by physicists and engineers around the world, the 20th century was without a doubt the Information and Communication Century. The development of the computer, personal communication devices and of the internet has changed the world we live in. But the physicists keep tinkering with our understanding of the laws of nature. Some of them are trying to control individual electrons, spins, atoms and photons. Others are asking whether a quantum computer would be much more powerful than the classical one, or whether it is possible to create an absolutely secure communication channel. This is the emerging area in physics of quantum computation and quantum information processing.
The present issue of Physics in Canada introduces quantum information and computation, presents some of the current issues in this area and gives a sample of the recent work done by physicists in Canada.
The issue starts with Ghose and Sanders, who give a review of open quantum systems and the quantum and classical boundary. The quantum systems are always embedded in a classical environment and the understanding of this boundary is important in selecting systems where quantum information processing can be achieved. The coupling of the quantum system to the environment leads to decoherence and errors. The question of whether one can carry quantum computation plagued by errors, called fault tolerant computation, is reviewed by Gottesman. This ability to correct errors without destroying a quantum state has been a critical development assuring that quantum information processing devices could be built in principle. This is also an important step toward the development of means to control quantum systems in a scalable way. The application of quantum systems in quantum cryptography is based on the fact that information gain by eavesdropping implies disturbance of quantum states. Quantum cryptography is a quickly developing field, with commercial systems already available. The path from theory to practical applications of quantum cryptography is reviewed by Lo and Lütkenhaus.
This is followed by a series of articles on quantum computing. The prototypes of rudimentary quantum computers are already available. They use nuclear spins, photons, Cooper pairs in superconductors, and electron spins in field effect transistors as qubits. Baugh et al. review recent progress in Quantum Information Processing using Nuclear Magnetic Resonance (NMR) and prospects for using electron spin resonance. A fundamental building block for quantum information processing using photons is a source of single photons on-demand and entangled photon pairs. Frederick et al. review recent progress in the application of semiconductor self-assembled quantum dots as sources of single photons. Zagoskin and Blais describe the application of macroscopic, solid state quantum circuits made of superconductors for quantum information processing, Finally, Korkusinski et al. describe progress in localizing, controlling and manipulating spins of individual electrons as qubits in semiconductor based field effect transistors.
This theme issue of Physics in Canada is not intended to give an authoritative review of this rapidly developing field, but is instead intended to highlight and showcase work done in Canada on Quantum Computing and Information. It is hoped that it will provide an overview and/or reference source for students and researchers entering this field.
Finally, we wish to thank all the Authors for their contributions and on their behalf, the Editorial Board, for the opportunity to share our excitement with quantum computation and information with the readers of Physics in Canada.
Pawel Hawrylak and Raymond Laflamme
Guest Editors, Physics in Canada
We invite our readers to submit comments on the contents of this editorial.
The Editorial Board welcomes articles from readers suitable for, and understandable to, any practising or student physicist. Review papers and contributions of general interest are particularly welcome.