Quantum mechanics is an extremely successful theory, but also a troubling one. For many years progress was made by concentrating on the obvious applications, and not worrying too much about the counterintuitive world view that quantum mechanics implies. More recently, however, the development of quantum-information theory has reversed this approach. If we take seriously what quantum mechanics seems to be telling us about the world, we can use this “quantum weirdness” to do apparently impossible things (see Physics World March 1998 pp33–57).
Quantum mechanics is an extremely successful theory, but also a troubling one. For many years progress was made by concentrating on the obvious applications, and not worrying too much about the counterintuitive world view that quantum mechanics implies. More recently, however, the development of quantum-information theory has reversed this approach. If we take seriously what quantum mechanics seems to be telling us about the world, we can use this “quantum weirdness” to do apparently impossible things (see Physics World March 1998 pp33–57).
Quantum mechanics occupies a unique position in the history of science. It has survived all experimental tests to date, culminating with the most precise comparison of any measurement to any theory – a 1987 measurement of the electron's magnetic moment, or gyromagnetic ratio g e = 2.002 319 304 39 (Van Dyck et al. 1987), agreeing with QED theory to 12 digits. Despite this and other dramatic successes of quantum mechanics, its foundations are often questioned, owing to the glaring difficulties in reconciling quantum physics with the classical laws of physics that govern macroscopic bodies. If quantum mechanics is indeed a complete theory of nature, why does it not apply to everyday life? Even Richard Feynman (1982), a fierce defender of quantum mechanics, memorably stated that: We have always had a great deal of difficulty in understanding the world view that quantum mechanics represents … Okay, I still get nervous with it … It has not yet become obvious to me that there is no real problem. I cannot define the real problem, therefore I suspect there's no real problem, but I'm not sure there's no real problem. In the dawn of the twenty-first century, John A. Wheeler's big question “Why the quantum?” has returned to the forefront of physics with full steam. Advances in experimental physics are beginning to realize the same thought-experiments that proved helpful to Einstein, Bohr, Heisenberg, Schrödinger, and the other founders of quantum mechanics.
Introduction Almost a century after its birth, quantum theory remains odd and counterintuitive. As Richard Feynman wrote, it seems that nobody really understands it. This is indeed true if by understanding we mean being able to explain it using our common sense and everyday experience. The development of some kind of “quantum common sense” has been very slow even though our everyday life is being continuously influenced by technologies whose roots lie in quantum laws. In recent years the growing field of quantum information and quantum computation became a fruitful playground for physicists, mathematicians, computer scientists, and researchers from other fields who developed new interesting ways of storing, transmitting, and processing information using quantum mechanics at its best. Thus, both theoretical and experimental research on multiparticle entanglement, on the manipulation of individual quantum systems, on decoherence, and on the transition from quantum to classical are subjects of interest not only for their basic relevance but also for their potential practical significance as they might be of help for the development of a real quantum computer. Even though this technology may be far in the future, it is interesting to speculate about what lessons on quantum reality could be learned from quantum computation (eg., what would happen if one could operate a quantum computer).
Quantum computing, quantum encryption and quantum teleportation: today's physics journals sound morelike Star Trek than ever. Based on the weird and counterintuitive features of quantum mechanics, these concepts have been brought to fruition in recent years by theorists and experimentalists alike. Indeed, these ideas are now leaving physics laboratories and being used by industry to make real products. Who knows what revolutions await in computation and communications from these budding breakthroughs?
Abstract Quantum theory provides a superb description of physical reality on a small scale, yet it contains many mysteries. Without doubt, it is hard to come to terms with the workings of this theory, and it is particularly difficult to make sense of the kind of ‘physical reality’—or lack of it—that it seems to imply for our world. Taken at its face value, the theory seems to lead to a philosophical standpoint that many (including myself) find deeply unsatisfying. At best, and taking its descriptions at their most literal, it provides us with a very strange view of the world indeed. At worst, and taking literally the proclamations of some of its most famous protagonists, it provides us with no view of the world at all.
“Anyone who is not shocked by quantum theory has not understood it.” Since Niels Bohr said this many years ago, quantum mechanics has only been getting more shocking. We now realize that it’s not really telling us that “weird” things happen out of sight, on the tiniest level, in the atomic world. Rather, we can now see that everything is quantum: our everyday world is simply what quantum becomes at the human scale. But if quantum mechanics is right, what seems obvious and right in our everyday world is built on foundations that don’t seems obvious or right—or even possible. An exhilarating tour of the contemporary quantum landscape, Beyond Weird is a book about what quantum physics really means—and what it doesn’t. Science writer Philip Ball offers an up-to-date, accessible account of the quest to come to grips with the most fundamental theory of physical reality, and to explain how its counterintuitive principles underpin the world we experience. Over the past decade it has become clear that quantum physics is less a theory about particles and waves, uncertainty and fuzziness, than a theory about information and knowledge—about what can be known, and how we know it. Discoveries and experiments over the past few decades have called into question the meanings and limits of space and time, cause and effect, and, ultimately, of knowledge itself. The quantum world Ball shows us isn’t a different world. It is our world, and if anything deserves to be called “weird,” it’s us.