The interpretation of quantum theory has always been a controversial subject. Since its inception early this century, it has been apparent that the rules that govern the quantum domain appear to be at odds with the familiar classical universe. Yet quantum theory is without doubt more fundamental. Whenever anything is investigated in detail, quantum rules invariably prevail, yielding correct predictions in all of the tested cases. But everything, including all of the objects we encounter in the "classical domain" of our everyday experience, is undoubtedly made out of quantum pieces. So how can it be that the quantum weirdness never makes it out of the quantum underworld? An ingenious experiment recently carried out at the Kastler-Brossel Laboratory of the Ecole Normale Supérieure in Paris has just begun to explore the quantum-classical boundary (M Brune et al. 1996 Phys. Rev. Lett. 77 4887).
The interpretation of quantum theory has always been a controversial subject. Since its inception early this century, it has been apparent that the rules that govern the quantum domain appear to be at odds with the familiar classical universe. Yet quantum theory is without doubt more fundamental. Whenever anything is investigated in detail, quantum rules invariably prevail, yielding correct predictions in all of the tested cases. But everything, including all of the objects we encounter in the "classical domain" of our everyday experience, is undoubtedly made out of quantum pieces. So how can it be that the quantum weirdness never makes it out of the quantum underworld? An ingenious experiment recently carried out at the Kastler-Brossel Laboratory of the Ecole Normale Supérieure in Paris has just begun to explore the quantum-classical boundary (M Brune et al. 1996 Phys. Rev. Lett. 77 4887).
Quantum mechanics works exceedingly well in all practical applications. No example of conflict between its predictions and experiment is known. Without quantum physics we could not explain the behavior of solids, the structure and function of DNA, the color of the stars, the action of lasers or the properties of superfluids. Yet well over half a century after its inception, the debate about the relation of quantum mechanics to the familiar physical world continues. How can a theory that can account ith precision for everything we can measure still be deemed lacking?
Ever since quantum theory was developed during the first quarter of the 20th century, we have lived with a strange division. Objects in our daily lives behave “normally” – they appear to obey classical physics – whereas microscopic objects can behave counter-intuitively and reveal intriguing features of quantum physics. But where exactly is the boundary between the quantum and classical worlds – if, indeed, there is one? If quantum physics is a universal theory, why is it respectable to talk about the quantum behaviour of electrons but not, say, of footballs?
Exploring quantum reality? Twentieth-century physics bequeaths us an unruly enigma in the equivocal dichotomy between quantum and classical. Mesoscopic systems: which are they, or when? To some this distinction is but a matter of modeling convenience; to others, the partition bears ontological weight. Whichever one's stance, debates on this issue sharpen our introspection on “Why the quantum?” by demanding rigorous justification for choices of calculative consequence, intuitively made on every day in every field of physics. The limits seem clear. For few particles, left to their own devices, quantum mechanics runs rampant with its nonclassical phenomenology, viz. superposition, tunneling, and entanglement. But for the largish objects of our everyday experience, the sensory familiarity of classical mechanics holds sway: each object has its (singular) place, and every obstacle must be gone round or over. Strange, then, to ponder how big things are made from small! Somehow the assemblage of perceivable matter inevitably converts quantum constituents to classical collective, as if the ordering of the universe were ruled by atoms' aversion to the public embarrassment of quantum behavior writ large. It's a shame in a sense, for the senses slighted of paranormal experience, but superposition … what would it look like anyway?
Abstract A scientist in the late nineteenth century could be forgiven for thinking that the major elements of physics were built on unshakeable foundations and effectively established for all time. The inspirational work of Galileo Galilei and Isaac Newton in the seventeenth century had been shaped by a further 200 years of theoretical and, in particular, experimental science into a marvellous construction which we now call classical physics. This physics appeared to explain almost every aspect of the physical world: the dynamics of moving objects, thermodynamics, optics, electricity, magnetism, gravitation, etc. So closely did theory agree with and explain experimental observations of the everyday world that there could be no doubt about its basic correctness- its essential ‘truth’. Admittedly, there were a few remaining problems but these seemed to be trivial compared with the fundamentals - a matter of dotting a few is and crossing some ts.
We observe non destructively photons trapped in a high Q cavity, generate quantum fields in “Schrödinger cat” like states and study their decoherence. Application of these studies to the processing of quantum information will be discussed. 150-word Biography: Serge Haroche, born in 1944 in Casablanca, graduated from Ecole Normale Supérieure (ENS), receiving his doctorate from Paris VI University in 1971. After a post-doctoral visit to Stanford University (1972-73), he became full professor at Paris VI University in 1975, a position he held until 2001, when he was appointed Professor at Collège de France. Since September 2012, he is the President (Administrateur) of this institution. Haroche’s research has mostly taken place in the laboratory Kastler Brossel at ENS. His main research activities have been in quantum optics and quantum information science. He has made important contributions to Cavity Quantum Electrodynamics (Cavity QED), the domain of quantum optics which studies the behaviour of atoms interacting strongly with the field confined in a high-Q cavity. An atom-photon system isolated from the outside world by metallic walls realizes a very simple experimental model which Serge Haroche and his team have used to test fundamental aspects of quantum physics such as state superposition, entanglement, complementarity and decoherence. Serge Haroche has received many prizes and awards, culminating in the 2012 Nobel Prize in physics, shared with David Wineland. Article not available.
In classical physics there is, in accordance with common sense, an objective world ‘out there’. That world evolves in a clear and deterministic way, being governed by precisely formulated mathematical equations. This is as true for the theories of Maxwell and Einstein as it is for the original Newtonian scheme. Physical reality is taken to exist independently of ourselves; and exactly how the classical world ‘is’ is not affected by how we might choose to look at it. Moreover, our bodies and our brains are themselves to be part of that world. They, also, are viewed as evolving according to the same precise and deterministic classical equations. All our actions are to be fixed by these equations - no matter how we might feel that our conscious wills may be influencing how we behave. Such a picture appears to lie at the background of most serious 1 philosophical arguments concerned with the nature of reality, of our conscious perceptions, and of our apparent free will. Some people might have an uncomfortable feeling that there should also be a role for quantum theory - that fundamental but disturbing scheme of things which, in the first quarter of this century, arose out of observations of subtle discrepancies between the actual behaviour of the world and the descriptions of classical physics. To many, the term ‘quantum theory’ evokes merely some vague concept of an ‘uncertainty principle’, which, at the level of particles, atoms or molecules, forbids precision in our descriptions and yields merely probabilistic behaviour. Actually, quantum descriptions are very precise, as we shall see, although radically different from the familiar classical ones. Moreover, we shall find, despite a common view to the contrary, that probabilities do not arise at the minute quantum level of particles, atoms, or molecules - those evolve deterministically - but, seemingly, via some mysterious larger-scale action connected with the emergence of a classical world that we can consciously perceive. We must try to understand this, and how quantum theory forces us to change our view of physical reality.