Quantum mechanics is money Text message and take a picture with your smart phone; watch a movie on your Blu-ray player; get the bar code on your bag of chips scanned; obtain an MRI image of your aching shoulder; take a ride on a maglev train. None of these—and countless other—things would be possible without quantum mechanics! Leon Lederman, Nobel Prize winning physicist, is widely quoted as saying that 1/3 of the world’s economy is due to quantum mechanics. Lederman’s estimate is actually probably too low, but what surely is the case is that computers, lasers, and superconducting magnets (to cite a few examples), and all of the very familiar products that rely on them, could not exist in their present forms without knowledge of the quantum mechanics of electrons and photons. A poignant demonstration of this is found in the image to the right. The large crate being “uploaded” to the Pan Am plane is 5 MB of computer memory. The flash drive shown would be only a dot on the side of the crate yet contains 1 Tb of memory— equivalent to about 200,000 crates (and, in today’s dollars, 10 million times cheaper). This huge advance in computer technology is directly due to applied quantum mechanics.
Quantum mechanics is money Text message and take a picture with your smart phone; watch a movie on your Blu-ray player; get the bar code on your bag of chips scanned; obtain an MRI image of your aching shoulder; take a ride on a maglev train. None of these—and countless other—things would be possible without quantum mechanics! Leon Lederman, Nobel Prize winning physicist, is widely quoted as saying that 1/3 of the world’s economy is due to quantum mechanics. Lederman’s estimate is actually probably too low, but what surely is the case is that computers, lasers, and superconducting magnets (to cite a few examples), and all of the very familiar products that rely on them, could not exist in their present forms without knowledge of the quantum mechanics of electrons and photons. A poignant demonstration of this is found in the image to the right. The large crate being “uploaded” to the Pan Am plane is 5 MB of computer memory. The flash drive shown would be only a dot on the side of the crate yet contains 1 Tb of memory— equivalent to about 200,000 crates (and, in today’s dollars, 10 million times cheaper). This huge advance in computer technology is directly due to applied quantum mechanics.
Unlike special relativity, quantum mechanics was not the inspired product of one mind. It developed, in fits and starts, over a period of 25 years (1900–1925), and many cooks stirred the broth. Even now, a century later, quantum mechanics raises profound conceptual questions. Every competent physicist can “do” quantum mechanics, and the predictions it makes are in spectacularly good agreement with experimental results; there can be little doubt that quantum mechanics is “right.” On the other hand, as Richard Feynman once remarked, “nobody understands quantum mechanics.” I'll tell the story in two parts. First the history (how the essential pieces of the puzzle were assembled), and then the implications (what the finished picture has to say about our world). Photons Like relativity, quantum mechanics began with the study of light. In both cases, this historical association is misleading. Relativity, really, has nothing to do with light – to be sure, it involves that magic speed limit, c , and of course the most familiar thing that travels at speed c is light. So light is a convenient vehicle for introducing the subject. But it is perfectly possible to imagine a universe in which there is no such thing as light, and yet relativity might still be valid. Quantum mechanics, too, starts with light – in this case the “quantum” of light (the photon). But, as it turns out, this is just one rather specialized example of much more general principles – in fact, a rather bad example, because photons are by their nature relativistic (they travel at the speed of light), and it would be more natural to begin with the quantum mechanics of slow-moving objects, in analogy with Newtonian mechanics.
What is usually called modern physics is based on two theories: relativity, which we have just nished discussing, and quantum mechanics (also called quantum theory). While some of the ideas of relativity, such as time dilation and length contraction, at rst seemed rather strange, we saw that they followed logically from the two postulates of relativity. We will see below that the ideas of quantum mechanics are also strange. Most physicists would agree that they are much stranger than relativity. In fact, we will see that there are no satisfactory explanations. To quote two Nobel Prize laureates, Murray Gell-Mann and Richard Feynman, “Nobody really understands quantum theory.” Despite this, it is one of the best-tested theories that we have. In some cases, the agreement between the theoretical prediction and experiment is better than 1 part in a million. There are many useful devices that are based on quantum mechanics. They include anything that uses microelectronics, such as a cell phone, DVD player, or computer, nuclear reactors, and medical imaging devices such as MRI and PET.
A picture is worth a thousand words" is one of the rare maxims phrased as an understatement.A high-resolution colour picture contains in fact more information (bit-wise) than a million words.It is in gene ral also faster, easier and more pleasant to grasp than mere words.Our brain is equipped with a rapid and efficient mechanism dedicated to analysing pictures and extracting meaning from them.In spite of our tremendous handicap in arith metic computations, we can still easily beat any computer when it comes to versatile image recognition.We are indeed so good at it that we like the exercise even better when the images are projected at the rate of at least 24 per second, in the form of video or film.For better or for worse, the dominant means of communication today is the ani mated image, and it is here to stay.But there are things we, as humans, would rather express in words, and there are things -quantum mechanics and field theory among them -that we, as scientists, would express more universally in equations and numbers.This should come as no sur prise, you might say: any fundamental theo ry is naturally presented in terms of defini tions, equations and constants of nature.True: but any fundamental theory is then developed and taught with the help of examples, demonstrations, experiments, applications, and images.Practitioners of quantum mechanics somehow managed with few of the last.The reasons for the scarcity of quantum images have very different origins, some valid, some unjustified.The following re marks illustrate the situation: -Quantum mechanics is manifest mainly at the molecular, atomic and subatomic scales.Only recently did microscopes beco me capable of producing "real" images at these scales.Some isolated coherent quan tum effects are known at larger scales (neu tron stars, lasers, superconductivity, liquid helium, etc.), but real images demonstrating clearly their quantum aspect are lacking.-In the domain of "theoretical" images, an overwhelming hurdle has been the rather
The turn of the XXth century witnessed a revolution in physics comparable to Isaac Newton’s discovery of the universal laws of mechanics and of gravitation three centuries earlier. The world required to be described in novel terms, as the immutable, deterministic view of our familiar universe had given way to a new world picture, one which featured chance, flux, and an incessant upsurge of waves of matter. Such a worldview was so radically new and counterintuitive that it gave rise to strong debates, to the effect that Albert Einstein himself tried to oppose it on the grounds that “God does not play dice”. In spite of the intense debates that accompanied its emergence, quantum mechanics quickly proved an incredibly efficacious new tool to understand and to predict a wide array of new phenomena. It was so successful that in no time it broke free from the environment of research labs to become part of daily life, making it possible, for example, to understand why some materials were conductors, while others were insulators. Along with it, came, too, the discovery of transistors, on which much of modern electronics rests. It also led to understand how novel materials known as superconductors allow the transport of electricity with no loss, thus paving the way for new developments in the fields of medical imagery or energy distribution. Other aspects of the quantum theory led to the development of atomic clocks of astounding accuracy, which would be wrong by no more than fifteen seconds, had they been set at the beginning of the universe. A hundred years later, at the turn of the XXIst century, Quantum mechanics has lost none of its astounding power. Contemporary research has undertaken the task of exploring its less immediately perceptible aspects. Groundbreaking developments have ensued, such as the teleportation of grains of light or the possibility, once predicted by the great physicist Richard Feynman, to build, one day, novel computers which, unlike the ones we are familiar with today, will be able to process innumerable numbers of operations in parallel. The Wright Colloquium will be for us the occasion to explore, in the company of five internationallyknown specialists in the field, some of the fascinating aspects of quantum mechanics. We will appraise how efficiently quantum physics can describe our world, and confront its limitation when it is faced with the infinitely small (in relation to recent experiments carried out at the CERN) as with the incommensurably large scale of sidereal spaces. We will appreciate the extent to which quantum physics already has impacted our everyday lives, and evoke the way in which novel fields such as quantum computers and quantum information will entail profound changes in the future. The quantum adventure has only just begun! Monday 15 November 2010 - 18h30 Jochen Mannhart Center for Electronic Correlations and Magnetism, University of Augsburg, Germany Quantum Physics on the Scale of Daily Life Tuesday 16 November 2010 - 18h30 Wolfgang Ketterle Nobel Laureate 2001 (Physics), Department of Physics, Massachusetts Institute of Technology, Cambridge, U.S.A. When freezing cold is not cold enough New forms of matter close to absolute zero temperature Wednesday 17 November 2010 - 18h30 David Gross Nobel Laureate 2004 (Physics), Kavli Institute for Theoretical Physics, University of California, Santa-Barbara, U.S.A. Quantum Mechanics of the Very, Very Small and the Very, Very Large Thursday 18 November 2010 - 18h30 Alain Aspect CNRS senior scientist and Professor Institut d'Optique and Ecole Polytechnique Palaiseau, France. From Einstein’s intuition to quantum bits: a new quantum age? Vendredi 19 novembre 2010 - 18h30 Rainer Blatt Institute of Quantum Optics and Quantum Information, Austrian Academy of Sciences and University of Innsbruck, Austria The Quantum Way of Doing Computations
Abstract When quantum theories were first formulated a century ago, who would have guessed how much technological developments originating from quantum physics shape the way we live and interact today. Whether we work on a computer, use our mobile phones, or get a diagnosis based on magnetic resonance imaging: The understanding of quantum mechanics is the basis for all these technologies. In photonics, the laser and light‐emitting diodes are prime examples, with a current market of more than 12 billion US dollars for lasers alone. Now there are new quantum technologies on the horizon, promising a second quantum revolution.
Quantum Mechanics is an essential topic in today's physics curriculum at both the undergraduate and graduate levels. Quantum mechanics can explain the microscopic world with fantastic accuracy; the fruits from its insights have created technologies that have revolutionized the world. Computers, lasers, mobile telephones, optical communications are but a few examples. The language of quantum mechanics is now an accepted part of the language of physics and day-to-day usage of this language provides physicists with the intuition that is essential for achieving meaningful results. Nevertheless, most physicists acknowledge that, at least once in their scientific career, they have had difficulties understanding the foundations of quantum theory, perhaps even the impression that a really satisfactory and convincing formulation of the theory is still lacking. Numerous quantum mechanics textbooks are available for explaining quantum formalism and applying it to understand problems such as the properties of atoms, molecules, liquids, and solids; the interactions between matter and radiation; and more generally to understand the physical world that surrounds us. Other texts are available for elucidating the historical development of this discipline and describing the steps through which it went before quantum mechanics reached its modern formulation. In contrast, books are rare that review the conceptual difficulties of the theory and then provide a comprehensive overview of the various attempts to reformulate quantum mechanics in order to solve these difficulties. The present text by Franck Laloë does precisely this.