October 2012
Press release Nobel Prize
The Assembly of Professors of the Collège de France is pleased to announce the award of the Nobel Prize in Physics 2012 to Professor Serge Haroche, Director of the Collège de France
The Nobel Prize in Physics 2012 has been awarded jointly to Serge Haroche in France and David Wineland in America for their research in the field of quantum physics. The Nobel Prize jury made the award for “ground-breaking experimental methods that enable measuring and manipulation of individual quantum systems” and stated that these two researchers had “opened the door to a new era of experimentation with quantum physics by demonstrating the direct observation of individual quantum particles without destroying them”.
The Assembly of Professors believes that this Nobel Prize pays tribute to the work of an exceptional researcher and his experimental successes. It honors the fundamental research which has been the mission of the Institution since its foundation. The Assembly would like to highlight the fact that this is the tenth Nobel Prize awarded to one of its professors, covering the widest range of disciplines after Harvard.
Claude Cohen Tannoudji, winner of the Nobel Prize in Physics in 1997, an honorary professor of the Collège de France and Serge Haroche’s PhD supervisor, stated that the prize recognized “a man with remarkable scientific and human qualities”.
Professor Serge Haroche has held the Chair in Quantum Physics at the Collège de France since 2001 and was appointed Director in September 2012. He began his career at the CNRS (French National Center for Scientific Research) and has carried out most of his research at the Kastler Brossel Laboratory (École normale supérieure/UPMC/CNRS/Collège de France), which specializes in the study of the interaction between light and matter. He heads the Electrodynamics of Simple Systems Group there.
Serge Haroche was initially interested in mathematics, but soon turned to physics; “I was fascinated by the fact that nature can be understood using mathematical laws and I was quickly drawn to physics, which added a major constraint to mathematics – namely reality”.
Atoms and light – thought experiments have become a reality
As a specialist in atomic physics and quantum optics, Serge Haroche is a pioneer of cavity quantum electrodynamics, a field which uses experiments to cast light on the fundamental principles of quantum theory and to produce prototypes based on quantum information processing. Working with his teams, he has designed innovative experimental methods to isolate, measure and manipulate single quantum particles for relatively long periods of time (about one-hundredth of a millisecond).
His research is aimed in particular at understanding the transition from the quantum world to the macroscopic world. This “decoherence” can now be observed using experiments with trapped photons, thus illustrating experimentally certain premises of quantum mechanics and fulfilling Albert Einstein’s dream of isolating and studying an atom or photon.
Although some like to dream of the ultra-powerful and fast supercomputers or extremely accurate clocks which could one day be developed using this research, Serge Haroche prefers to point out that what takes precedence is the desire to understand the world around us, the importance of fundamental research and the fact that the applications facilitated by this fundamental research often take even scientists themselves by surprise. “The majority of modern technologies which very often have their basis in quantum physics, such as transistors, lasers and MRI imaging, are the outcome of chance and the convergence of fundamental research activities which were not focusing on that specific goal. Chance and time are also key elements of fundamental research.”
Professor Serge Haroche’s lectures are available in audio or video format on the Collège de France website (www.college-de-france.fr).
Press contact: Marie Chéron/Cécile Barnier: +33 (0)1 44 27 12 72 - [email protected] October 2012
Serge Haroche’s research field
When thought experiments become a reality
The world is made up of atoms which emit, absorb and diffuse light, the essential vehicle for the information which we receive about our environment. At the beginning of the last century, quantum theory uncovered the enigmatic laws obeyed by matter and radiation at a microscopic level, in a counter-intuitive world in which the notions of waves and particles are closely intertwined. Light is both a continuous stream and a collection of discrete photons. This enigmatic area of physics is based on the principle of superposition. A microscopic system can actually exist in several possible states simultaneously, suspended as it were between various classical realities.
The founding fathers of quantum theory based their famous discussions on thought experiments, manipulating atoms and photons in the virtual realm. Experiments which for a long time were the stuff of dreams then are now being carried out at last. Juggling with atoms and photons and making them interact in a controlled environment is a now a thriving field of experimental research in which Serge Haroche is a pioneer. He has forced an atom to interact with several photons in a “photon box” whose walls offer an almost ideal degree of reflectivity, something of which Bohr and Einstein could only previously dream. He has thus been able to observe the atom-light interaction in its most basic form. Serge Haroche and the ENS team, which he currently leads with the co-authors of this article, were trail blazers in the field of cavity quantum electrodynamics, which has evolved significantly over the last thirty years.
Although simple in theory, the ENS experiments are technically complex. Cavities, which are resonant in the microwave field, are comprised of superconducting mirrors which face each other; these are the highest quality mirrors currently available, off which light bounces several billion times before being absorbed or diffused. The photons therefore travel 40,000 kilometers in the confined 3 cm space between the mirrors, giving the experimenters 13 hundredths of a second to manipulate or observe them. The atoms which interact with these photons are also very unusual. They are atoms in which a single electron has been put into a highly excited orbit, with a radius (0.1µm) which is 2,500 times greater than that of the atom in its basic state. Extensive research has been carried out on these Rydberg atoms in the last thirty years. Serge Haroche was a pioneer of this research in the 1970s, demonstrating the extreme sensitivity of these atoms to microwaves and developing methods to prepare, manipulate and detect them.
Using these ground-breaking tools, Serge Haroche and the ENS team have, for example, recently developed a revolutionary new method for counting photons. Standard detection methods (including the human eye) destroyed the photons they counted, but the team has perfected a “transparent” detection method in which photons interact with the counting equipment, without being absorbed. The experiment consists of making the field, which is trapped in the cavity, interact with atom “probes”. They pass through the cavity one by one carrying an imprint of the state of the field without absorbing light energy. Information relating to the number of photons is acquired progressively, as each atom is detected, making a partial contribution to determining the state of the field. When a photon subsequently disappears, absorbed by the imperfections in the mirrors, the energy in the field undergoes a sudden and discontinuous variation which is detected by the atoms. These quantum jumps, a fundamental quantum principle, had never been observed in relation to light prior to this experiment.
The Zeno effect is another spectacular quantum phenomenon illustrated by these experiments. Adopting a paradoxical line of argument, the Greek philosopher Zeno denied the existence of the movement of an arrow, claiming that it was immobile because it was located in a specific place at any given instant. A succession of immobile states cannot constitute movement. This sophism is of course false in the macroscopic world, but it can become true in quantum physics where observation influences the object being measured. The ENS team has demonstrated that the evolution of a field which they attempt to inject into the cavity is frozen if the number of photons is counted repeatedly and non-destructively. Quantum physics therefore proves that Zeno was right, but the reasons advanced are far more subtle than those posited by the philosopher!
Atoms and cavities can also be used to explore the quantum-classical boundary. In a key experiment, Serge Haroche and his colleagues monitored the state of a field containing several photons and a single atom. The field was in a quantum superposition of two radically different states. In practice, the atom controls the oscillation
Press contact: Marie Chéron/Cécile Barnier: +33 (0)1 44 27 12 72 - [email protected] October 2012
phase, but it is equally valid and simpler to work on the basis that it controls amplitude. After interacting with the atom, the field is in a superposition of a state in which it oscillates strongly (high amplitude) and a state in which it does not oscillate at all (zero amplitude). This situation is impossible in the classical world, but falls within the laws of quantum physics. Such states are referred to as Schrödinger’s cat states, after a thought experiment in which an imaginary cat was sealed in a box with a radioactive atom and placed in the awkward position of being suspended between life and death in quantum terms.
In the real world, a cat is either dead or alive! This is where “decoherence” enters the picture. When macroscopic objects are coupled with their environment their superposition of states rapidly disappears. Quantum ambiguity is replaced by the classical world of everyday experience. The ENS team has successfully traced this phenomenon in real time by observing the development of a “Schrödinger’s cat” state comprising several photons. This proves that the larger the number of photons, the shorter the decoherence time. This explains why macroscopic systems formed from a gigantic number of particles always appear to be classical.
Looking beyond thought experiments, cavity electrodynamics plays an important part in the development of quantum information, the branch of science which is striving to exploit the enigmatic logic of the quantum world to process information. In conventional computers, information is coded as traditional bits with exclusive values of 0 or 1. Quantum information uses quantum bits or “qubits” which can exist in a superposition of states 0 and 1.The principle of superposition opens up a huge number of possibilities. Machines which could juggle these qubits could carry out certain types of calculation faster than current computers, or make the secret of the information communication secure. The ENS team was very quickly able to produce the basic building blocks for this machine. Rydberg atoms will probably not be the qubits of the devices of the future, but they have played their part in demonstrating the feasibility of calculations which have now been followed up with systems which are easier to integrate such as circuit quantum electrodynamics which uses microwave resonators made up of parallel wires on a chip and superconductor junctions instead of Rydberg atoms.
Serge Haroche has recently been awarded the Nobel Prize in Physics 2012 for his research jointly with David J. Wineland from NIST (USA). Their two approaches complement each other. The ENS team traps a few elementary particles of light and photons and manipulates them with elementary particles of matter in the form of atoms. The NIST team traps a few particles of matter (ions) and manipulates their quantum state using lasers, i.e. beams of photons. These two teams have made very similar and sometimes simultaneous discoveries. Their research is stimulated by pure intellectual curiosity. Turning thought experiments into reality involves complex methods and sustained effort, which these two teams have been able to achieve by virtue of stable funding and the generous input of generations of exceptional students and postdoctoral researchers. This work belongs to the realms of pure research and is inconceivable without the constant interaction between fundamental and applied research. It relies on technological advances and yet it will inspire the development of new equipment.
Jean-Michel Raimond, Professor at the Pierre and Marie Curie University, Honorary Member of the Institut Universitaire de France Michel Brune, Research Director at the CNRS
Jean-Michel Raimond and Michel Brune have been working with Serge Haroche since respectively 35 and 27 years in Kastler Brossel laboratory
Press contact: Marie Chéron/Cécile Barnier: +33 (0)1 44 27 12 72 - [email protected] October 2012
The Collège de France, a unique institution
Director, Chairman of the Assembly of Professors: Professor Serge Haroche, holder of the Chair in Quantum Physics Vice‐Chairman: Professor John Scheid, holder of the Chair in Religion, Institutions and Society in Ancient Rome
Founded in 1530 by Francis I, the Collège de France remains a unique institution.
Originally providing six chairs in Hebrew, Greek and mathematics, subjects which were not recognized by the University at that time, the institution has developed over five centuries based on its motto: Docet omnia (All things are taught).
It now has 57 chairs covering a very wide variety of disciplines ranging from mathematics to the study of great civilizations, including life sciences, social sciences and economics, physics, chemistry, linguistics, history, philosophy and sustainable development, to name but a few. Lectures are free and open to all without tuition fees. Although many students attend lectures, the Collège de France is not a degree‐awarding institution. The 6 former lecteurs royaux are now 57 professors of different nationalities chosen by their peers on the basis of the quality of their work and their contribution to their disciplines.
Freedom of research From the very outset, the basic premise that chairs are not permanent has underpinned the creative energy of this academic community. Therefore, when incumbents retire, new appointments are made on the basis of the very latest scientific developments. New members are elected by the Assembly of Professors. There is no specific academic rank stipulated for nominees; the only relevant factors are the significance and originality of their work. The option to modify chairs is a principal which avoids the rigidity of fixed academic disciplines. The Collège de France is therefore permanently adapting to developments in the sciences and remains a focal point for the scientific community.
In recent years, the Collège de France has created five annual chairs to abreast of developments in society: a Chair in Artistic Creation, first held by the French architect Christian de Portzamparc (2004); a Chair in Technological Innovation – Liliane Bettencourt, the first chair to be financed entirely with private funds (2007); * a Chair in Knowledge against Poverty (2008) ; a Chair in Sustainable Development – Environment, Energy and Society (2008)* and finally a Chair in Computer Science (2009)*.
Nearly five centuries after its foundation, the Collège de France therefore continues to pursue its unique mission of “teaching knowledge in the making” in every field of literature, the arts and sciences.
At the Collège de France, education and research go hand in hand. Many laboratories and libraries are spread out across the institution’s different sites in Paris (place Marcelin Berthelot, rue d’Ulm – Institute for the Contemporary World, rue Cardinal Lemoine – Institute of Civilizations). Three phases of work (1992‐2013) are enabling several buildings to be refurbished and new biology, chemistry and physics laboratories covering 16,000 m2 in the very heart of Paris to be created with the institution’s own funds and with major funding from the French Ministry for Higher Education. The Collège de France has been the beneficiary of sponsorship funding allowing it to expand the scientific activity of its annual chairs, to support the development of its libraries and laboratories and to foster the dissemination of knowledge via its International Digital Campus (www.college‐de‐France.fr).
Research The research programs of Collège de France chairs and partnerships with institutions in France (including the CNRS, INSERM and the Institut Pasteur) and abroad also place the French institution in the ranks of world‐class research organizations and French thought in the wider world. This is also a unique place, where Nobel Prize
* These three chairs have been created with assistance from sponsors.
Press contact: Marie Chéron/Cécile Barnier: +33 (0)1 44 27 12 72 - [email protected] October 2012
winners rub shoulders with winners of Fields Medals, the Abel Prize or the Balzan Prize.
Laboratories and institutes The Collège de France laboratories and five specialist institutes (Institute of Biology, Institute of the Contemporary World, Oriental Institute, Institute of Literary Studies and the CIRB) play host to researchers and young guest teams working on medium‐term programs. Internal, hosted or external teams are always affiliated to other research bodies with specialist infrastructures, so that they can work over the long‐term, retaining a degree of flexibility which is the key to innovation.
Disseminating knowledge Lectures, symposia and seminars are attended by a growing number of people in the Collège de France lecture theatres (140,000 per year). Publications and broadcasts of our research and education activities on the France Culture radio station, increase audience reach. However, its key asset is its innovative and pioneering launch of an International Digital Campus in 2007.
Recordings of inaugural lectures, regular lectures and symposia are also available as podcasts in audio and/or video format on the institution’s website and on iTunes U, Youtube or Dailymotion (8,000,000 hours of content downloaded in 2011). These recordings are often supplemented by lecture notes and/or resources. The catalogue of electronic publications is also enhanced on a daily basis. This form of broadcasting throws the doors to the Collège de France and its knowledge base wide open.
Building on this success, the institution is making an even larger contribution to the dissemination of French science with a program to interpret lectures and to translate resources into English. Some lectures are also interpreted into Portuguese and Chinese.
Libraries The Collège de France has valuable resources in the form of rare books and specialist libraries, including libraries specializing in the Near East and Far East (China, Japan, Korea, India, Tibet), as well as the very extensive library of social anthropology, Asiatic society, Byzantium and Egyptology. They house some of the largest and finest collections in Europe.
Fully refurbished premises covering 2,000 m2 offer optimum reading and research conditions for French and overseas researchers. Furthermore, from November 2012, the institution’s archives will be available online and it will be possible to access digitally scanned volumes remotely.
International reach Professors have the opportunity to deliver one third of their education activity in French universities outside Paris or universities abroad. A large percentage of this activity takes the form of partnership agreements, signed with universities in more than fifteen countries around the world or in collaboration with French Institutes.
Every year, the Assembly of Professors of the Collège de France invites over forty notable scientific figures from abroad to deliver a series of lectures. The program to host “young researchers” from abroad extends a welcome to colleagues from all over the world. Lastly, the International Digital Campus offers access to all research and education at the Collège de France.
A desire exists to combine forces and unify and exploit synergies in order to create a world‐class research campus. The Collège de France is developing a policy of greater openness beyond its own campus. Working alongside the ENS, the institution has supported a project for forging links between major establishments in the Montagne Sainte‐Geneviève academic district of Paris in the firm belief that this collaboration offers a unique opportunity to improve synergies, support large‐scale projects, develop the impact and appeal of these institutions abroad, and further to enhance the excellence of these associated institutions.
The Collège de France is the founding member of the Fondation de coopération scientifique Paris Sciences et Lettres, alongside the ENS, the Observatoire de Paris, ESPCI ParisTech and Chimie ParisTech, Dauphine and a dozen other establishments. This excellence cluster will add an extra dimension to the activities of the Collège de France.
Press contact: Marie Chéron/Cécile Barnier: +33 (0)1 44 27 12 72 - [email protected] October 2012
Facts and figures: The Collège de France currently boasts • 2 Abel Prize winners • 4 Fields medalists • 7 Balzan Prize winners 10 Nobel Prize winners. The latest Nobel Prize winner is Professor Serge Haroche, holder of the Chair in Quantum Physics, who was awarded the Nobel Prize in Physics, in 2012.
A few figures . 57 areas of research (Mathematics, Social sciences, Life Sciences, Physics, Chemistry, History, Archaeology, the Environment,Technological Innovation, Digital Sciences, Egyptology, etc.) . 5 Institutes (Institute of Biology, Institute of the Contemporary World, Oriental Institute, Institute for Literary Studies, CIRB) . 300 researchers . 310 engineers, technicians and administrative employees . 133 advanced PhD and post‐doctoral researchers . 12 guest research teams . A heritage of rare books and specialist libraries which are among the finest in Europe . 8 million hours of lectures downloaded in 2011 . 150,000 people attend lectures every year
Press contact: Marie Chéron/Cécile Barnier: +33 (0)1 44 27 12 72 - [email protected] October 2012
The Kastler Brossel Laboratory (LKB) The Kastler Brossel Laboratory (LKB), where Serge Haroche has carried out the majority of his research and where he heads the Electrodynamics of Simple Systems Group, was founded in 1952 by Alfred Kastler (CNRS Gold Medal 1964, Nobel Prize 1966) and Jean Brossel (CNRS Gold Medal 1984) to explore the interaction between light and matter. Their research on optical pumping and their teaching provided the initial impetus and created a research-based culture in the laboratory which bears their names today. The Kastler Brossel Laboratory has become one of the major global players in the fundamental physics of quantum systems today. The LKB is multidisciplinary and conducts research ranging from fundamental interactions and the basic principles of quantum mechanics right through to medical imaging. All of these activities are closely linked to the laboratory’s expertise in the interaction between matter and radiation at a quantum level.
Press contact: Marie Chéron/Cécile Barnier: +33 (0)1 44 27 12 72 - [email protected]