“Anyone who has not been shocked by quantum physics has not understood it.”
—Niels Bohr

For all of recorded history human beings have sought to understand ever more deeply the nature of the world around them. It is fair to say that quantum theory (and its offspring, quantum field theory) is the most detailed and successful scientific description of nature we have ever achieved. But it is also one of the strangest, built on counterintuitive features like “superposition” (e.g. a single particle can behave as if it is in many places simultaneously) and “entanglement” (e.g. two particles, even widely separated in space, can behave in some ways as a single entity). After its development in the 1930s by great thinkers such as Max Planck, Niels Bohr, Werner Heisenberg, Erwin Schroedinger and others, it took the scientific community a long time to come to grips with what the theory is telling us about the nature of reality. And even today there are still very deep unresolved mysteries at the conceptual level.

Fortunately, this inherent mysteriousness has not prevented a whole host of spectacular applications of the theory, including the transistor (the basis of much of our current computing technology), the laser (the basis of today’s fibre optic communications networks and many other technologies), MRI (Magnetic Resonance Imaging devices crucial to modern medicine), SQUIDs (Superconducting Quantum Interference Devices used to search for new oil deposits or scan magnetic activity in the brain) and many more. Over the decades since its discovery, understanding of quantum theory has spread from theoretical and experimental physicists to applied physicists and engineers—building practical devices for science and commerce—and finally to the public at large, as witnessed by the many popular books today that intrigue the curious with the sheer weirdness of quantum ideas.

Arguably the most important development in this cycle has been the birth of the new field of science called quantum information theory. It is well-known that modern computers process information based on laws of nature that date back to Galileo and Newton. Theoretical physicists such as Richard Feynman, David Deutsch and others wondered if it might be possible to build an entirely new kind of computer based, instead, on the more accurate and powerful quantum laws, i.e. a quantum computer. It was realized that such a computer would be vastly more powerful than any conventional computer could ever be. Subsequent developments have now brought us to the brink of what might be called the “quantum information age”. On the horizon are wildly fantastic possibilities, including: quantum computers, absolutely secure quantum communication systems and quantum teleportation, to name a few. A more detailed description of the ideas and future potential of quantum information theory can be found here.

Suggested Reading

• Julian Brown, Minds, Machines, and the Multiverse: The Quest for the Quantum Computer (Simon & Schuster, 2000)
• David Deutsch, The Fabric of Reality: The Science of Parallel Universes—and Its Implications (Penguin Books, 1997)
• Gerard Milburn, Schrodinger’s Machines: The Quantum Technology Reshaping Everyday Life (W H Freeman & Co, 1997)