Quantum mechanics is the most ground-breaking and fascinating theoretical concept developed in physics during the past century. Much of our present understanding of the microscopic world and its extension into the macroscopic world, including modern technical applications, is based upon quantum mechanics. We have experienced a remarkable development of information and communication technology during the past two decades, to a large extent depending upon successful fabrication of smaller and smaller components and circuits. However, we are finally approaching the physical limits of component miniaturization as we enter a microscopic world ruled by quantum mechanics. Present technology is mainly based upon classical physics such as mechanics and electromagnetism. We now face a similar paradigm shift as was experienced two hundred years ago, at the time of the industrial revolution. Engineered construction of systems is currently increasingly based on quantum physics instead of classical physics, and quantum information is replacing much of classical communication. Quantum computing is one of the most exciting sub-fields of this revolution. Individual quantum systems can be used to store and process information. They are called quantum bits, or qubits for short. A quantum computer could eventually be constructed by combining a number of qubits that act coherently. Important computations can be performed much more quickly than by classical computers. However, while we control and measure a qubit, it must be sufficiently isolated from its environment to avoid noise that causes decoherence at the same time. Currently, low temperature is generally needed to obtain sufficiently long decoherence times. Single qubits of many different kinds can be built and manipulated; some research groups have managed to successfully couple qubits and perform rudimentary logic operations. However, the fundamental problems, such as decoherence, entanglement, quantum measurements and error correction, have yet to be solved. It has been predicted that quantum computers will be able to perform certain complicated computations or simulations in minutes or hours instead of years as with present computers. So far there exist very few useful quantum algorithms; however there is hope that the development of these will be stimulated once there is a breakthrough in hardware. Remarkable progress has been made in quantum engineering and quantum measurements, but a large scale quantum computer is still far off. Quantum communication and cryptography are much closer to the market than a quantum computer. The development of quantum information has meant a large push in the field of quantum physics, that previously could only be studied in the microscopic world. Artificial atoms, realized by circuit technology and mimicking the properties of 'natural' atoms, are one example of the new possibilities opened up by quantum engineering. Several different types of qubits have been suggested. Some are based upon microscopic entities, like atoms and ions in traps, or nuclear spins in molecules. They can have long coherence times (i.e. a long period allowing many operations, of the order of 10 000, to be performed before the state needs to be refreshed) but they are difficult to integrate into large systems. Other qubits are based upon solid state components that facilitate integration and coupling between qubits, but they suffer from interactions with the environment and their coherent states have a limited lifetime. Advanced experiments have been performed with superconducting Josephson junctions and many breakthroughs have been reported in the last few years. They have an advantage in the inherent coherence of superconducting Cooper pairs over macroscopic distances. We chose to focus the Nobel Symposium on Qubits for Future Quantum Information on superconducting qubits to allow for depth in discussions, but at the same time to allow comparison with other types of qubits that may prevail in the long run. The purpose of the symposium was to bring together leading researchers in adjoining fields. Often, microscopic qubits are considered at conferences within atomic, molecular and optical physics, while macroscopic ones belong to the solid state community. At the symposium, we experienced objective comparisons between different types of qubits—pros and cons as well as prospects. One example was the topic of quantum electrodynamics of superconducting circuits where qubits are coupled to a high- Q microwave resonator. This breakthrough technology was covered in several talks and was compared, in detail, with the corresponding case of light coupled to atoms in a cavity. A highlight was the presentation of how arbitrary photon states can be created in a cavity and the measurement of the corresponding Wigner functions. A Nobel Symposium provides an excellent opportunity to bring together a group of outstanding scientists for a stimulating exchange of ideas and results. The present symposium took place in Gothenburg, 25–28 May 2009. In order to allow local researchers and students to get a feeling of what is happening in the field, the first day of the symposium was held at the Chalmers campus. The remaining three days were spent at the mansion built by William Chalmers, the benefactor behind Chalmers University of Technology. Thirty-three speakers gave popular lectures open to the general public, overviews of different types of qubits, quantum phenomena, and quantum computing requirements, as well as specialized contributions in six sessions, and ten posters were displayed. The list of participants, program, abstracts and summaries of presentations is given at www.chalmers.se/mc2/EN/nobel-symposium-2009 . In order to encourage constructive interactions and discussions, ample time was given to extensive critical discussions and to individual meetings in relaxing and stimulating environments. Questions and discussions followed all talks but longer, more extensive, discussions of about one hour ended each session. These discussions were initiated by a special questioner (a kind of 'devil's advocate'). Receptions were given by the President of Chalmers and by the City of Gothenburg. The participants also sailed with SS Bohuslän in the archipelago outside the city. The symposium was sponsored by the Nobel Foundation through its Nobel Symposium Committee and was organized by Thilo Bauch, Tord Claeson, Per Delsing, Ann-Marie Frykestig, Eva Hellberg, Göran Johansson, Göoran Wendin, and Chris Wilson. Special thanks are given to the program committee: John Clarke, Daniel Estève, Steve Girvin, Anne l'Huillier, Anthony Leggett, and Mikko Paalanen. The editor of the proceedings is Göran Johansson.
Quantum mechanics is the most ground-breaking and fascinating theoretical concept developed in physics during the past century. Much of our present understanding of the microscopic world and its extension into the macroscopic world, including modern technical applications, is based upon quantum mechanics. We have experienced a remarkable development of information and communication technology during the past two decades, to a large extent depending upon successful fabrication of smaller and smaller components and circuits. However, we are finally approaching the physical limits of component miniaturization as we enter a microscopic world ruled by quantum mechanics. Present technology is mainly based upon classical physics such as mechanics and electromagnetism. We now face a similar paradigm shift as was experienced two hundred years ago, at the time of the industrial revolution. Engineered construction of systems is currently increasingly based on quantum physics instead of classical physics, and quantum information is replacing much of classical communication. Quantum computing is one of the most exciting sub-fields of this revolution. Individual quantum systems can be used to store and process information. They are called quantum bits, or qubits for short. A quantum computer could eventually be constructed by combining a number of qubits that act coherently. Important computations can be performed much more quickly than by classical computers. However, while we control and measure a qubit, it must be sufficiently isolated from its environment to avoid noise that causes decoherence at the same time. Currently, low temperature is generally needed to obtain sufficiently long decoherence times. Single qubits of many different kinds can be built and manipulated; some research groups have managed to successfully couple qubits and perform rudimentary logic operations. However, the fundamental problems, such as decoherence, entanglement, quantum measurements and error correction, have yet to be solved. It has been predicted that quantum computers will be able to perform certain complicated computations or simulations in minutes or hours instead of years as with present computers. So far there exist very few useful quantum algorithms; however there is hope that the development of these will be stimulated once there is a breakthrough in hardware. Remarkable progress has been made in quantum engineering and quantum measurements, but a large scale quantum computer is still far off. Quantum communication and cryptography are much closer to the market than a quantum computer. The development of quantum information has meant a large push in the field of quantum physics, that previously could only be studied in the microscopic world. Artificial atoms, realized by circuit technology and mimicking the properties of 'natural' atoms, are one example of the new possibilities opened up by quantum engineering. Several different types of qubits have been suggested. Some are based upon microscopic entities, like atoms and ions in traps, or nuclear spins in molecules. They can have long coherence times (i.e. a long period allowing many operations, of the order of 10 000, to be performed before the state needs to be refreshed) but they are difficult to integrate into large systems. Other qubits are based upon solid state components that facilitate integration and coupling between qubits, but they suffer from interactions with the environment and their coherent states have a limited lifetime. Advanced experiments have been performed with superconducting Josephson junctions and many breakthroughs have been reported in the last few years. They have an advantage in the inherent coherence of superconducting Cooper pairs over macroscopic distances. We chose to focus the Nobel Symposium on Qubits for Future Quantum Information on superconducting qubits to allow for depth in discussions, but at the same time to allow comparison with other types of qubits that may prevail in the long run. The purpose of the symposium was to bring together leading researchers in adjoining fields. Often, microscopic qubits are considered at conferences within atomic, molecular and optical physics, while macroscopic ones belong to the solid state community. At the symposium, we experienced objective comparisons between different types of qubits—pros and cons as well as prospects. One example was the topic of quantum electrodynamics of superconducting circuits where qubits are coupled to a high- Q microwave resonator. This breakthrough technology was covered in several talks and was compared, in detail, with the corresponding case of light coupled to atoms in a cavity. A highlight was the presentation of how arbitrary photon states can be created in a cavity and the measurement of the corresponding Wigner functions. A Nobel Symposium provides an excellent opportunity to bring together a group of outstanding scientists for a stimulating exchange of ideas and results. The present symposium took place in Gothenburg, 25–28 May 2009. In order to allow local researchers and students to get a feeling of what is happening in the field, the first day of the symposium was held at the Chalmers campus. The remaining three days were spent at the mansion built by William Chalmers, the benefactor behind Chalmers University of Technology. Thirty-three speakers gave popular lectures open to the general public, overviews of different types of qubits, quantum phenomena, and quantum computing requirements, as well as specialized contributions in six sessions, and ten posters were displayed. The list of participants, program, abstracts and summaries of presentations is given at www.chalmers.se/mc2/EN/nobel-symposium-2009 . In order to encourage constructive interactions and discussions, ample time was given to extensive critical discussions and to individual meetings in relaxing and stimulating environments. Questions and discussions followed all talks but longer, more extensive, discussions of about one hour ended each session. These discussions were initiated by a special questioner (a kind of 'devil's advocate'). Receptions were given by the President of Chalmers and by the City of Gothenburg. The participants also sailed with SS Bohuslän in the archipelago outside the city. The symposium was sponsored by the Nobel Foundation through its Nobel Symposium Committee and was organized by Thilo Bauch, Tord Claeson, Per Delsing, Ann-Marie Frykestig, Eva Hellberg, Göran Johansson, Göoran Wendin, and Chris Wilson. Special thanks are given to the program committee: John Clarke, Daniel Estève, Steve Girvin, Anne l'Huillier, Anthony Leggett, and Mikko Paalanen. The editor of the proceedings is Göran Johansson.
Quantum Information Science is a cross-disciplinary subject that has arisen in the last twenty years. It concerns itself with the consequences of our most complete description of the physical world (that is, quantum mechanics) for the reliable, secure, private, and rapid processing of information, both in communication and computation. While its invention is often ascribed to the famous theoretical physicist Richard Feynman in the 1980s, his contributions were only one of many that initiated the field around that time. While he perceived that new types of physical devices, in which the quantum laws of superposition and entanglement function at the logical level, could give new power in the simulation of quantum physics, it was others (Bennett, Brassard) who showed that the uncertainty principle led to fundamentally more secure ways of communicating secret messages. It was yet others (Deutsch, Vazirani) who understood that quantum theory defined a new kind of Turing machine, and that not only quantum physics simulations, but potentially many other computational problems, are sped up in this machine. And it was yet another (Shor) who found a simple, very fast algorithm for prime factorization. The word "qubit" was coined only in 1995. Its introduction is indicative of a new mindset that has developed in recent years for studying and using quantum systems. "Qubit" now stands for a durable paradigm that spans a very wide variety of fields. It thus has many sub-meanings: first, it is the basic abstract unit of information for workers ranging from optical communication engineers to NMR spectroscopists to black-hole theorists. Second, it is the name we now routinely give to physical two level systems, as they are realized by photons, atomic and ionic eigenlevels, electronic and nuclear spin, structural defects in solids, and circulating-current states of superconducting devices. Physics has long dealt with some of these two-level systems, but calling them qubits implies a whole suite of interrelated ideas and capabilities that we ascribe to these systems: the ability to precisely set, and to precisely measure, the quantum state of one unique specimen, to avoid its coupling with the environment while at the same time strongly and controllably coupling the qubits together, to exploit the resulting quantum entanglement as a resource for metrological, cryptographic, and computational tasks. Quantum Information is a very diverse subject pursued today in many different directions, by many hundreds of researchers internationally: In theoretical physics, it has enlivened and sharpened the understanding of efficient representations of entangled many-particle wavefunctions, and has provided the prospect of applications for new concepts such as anyons and majorana fermions. Information theorists has benefitted from having a rigorous extension of the basis of their field, in which classical information theory is subsumed into a greatly broader subject. Theoretical computer scientists continue the search for new quantum algorithms, and have used quantum concepts to prove new results about the classification of computational complexity. Coding theorists have had the new and subtle problem of quantum error correction to analyse and conquer. Most strikingly, the program of experimental physics has been influenced in many directions by Quantum Information Science. State-of-the-art optics experiments transmit quantum states over long distances and perform precision manipulations in single quanta (atomic ions, impurity spins, quantum dots) in the quest to have working quantum cyptography and quantum computing. Quantum Hall systems, and topological insulators, are being assiduously examined for new elementary excitations for use as qubits. In the course of ten years, superconducting devices have improved by over four orders of magnitude in their quantum coherence, a metric made precise by the ideas of quantum computing. [...] DiVincenzo, David
Quantum mini-toc
In a world overwhelmed by increasing amounts of data, finding new ways to store and process information has become a necessity. Conventional silicon-based electronics has experienced rapid and steady growth, thanks to the progressive miniaturization of its basic component, the transistor, but that trend cannot continue indefinitely.
![Figure][1]
CREDIT: PHOTO: CURT SUPLEE AND EMILY EDWARDS, JOINT QUANTUM INSTITUTE AND UNIVERSITY OF MARYLAND; CHIP FABRICATION: SANDIA NATIONAL LABORATORIES WITH SUPPORT FROM THE INTELLIGENCE ADVANCED RESEARCH PROJECTS ACTIVITY
In conventional devices, information is stored and manipulated in binary form: The elementary components of these devices—the so-called bits—have two states, each of which encodes the binary 0 or 1. To move beyond the binary system, one can exploit the laws of quantum mechanics. A quantum-mechanical object with two energy levels at its disposal can occupy either of those two levels, but also an arbitrary combination (superposition) of the two, much like an electron in a two-slit experiment can go through both slits at once. This results in infinitely many quantum states that a single quantum bit, or qubit, can take; together with another strange property of quantum mechanics—entanglement—it allows for a much more powerful information platform than is possible with conventional components.
Quantum information processing (QIP) uses qubits as its basic information units. QIP has many facets, from quantum simulation, to cryptography, to quantum computation, which is expected to solve problems more complex than those within the capabilities of conventional computers. To be useful for QIP, a qubit needs to be both isolated from its environment and tightly controllable, which places stringent requirements on its physical realization. But this is only the first step; to build a quantum computer, for example, we must also have a scalable architecture and error correction that can be performed in parallel with computation; in addition, efficient quantum algorithms must exist for solving the problem at hand—a considerable theoretical challenge.
A number of qubit types have been proposed and experimentally realized that satisfy at least some of these criteria, and tremendous progress has been made over the past decade in improving the figures of merit, such as the coherence time. In this special section, four Reviews look into the future of QIP in some of its most promising physical realizations. On p. [1164][2], Monroe and Kim discuss the challenges of scaling trapped ion architectures to hundreds and thousands of qubits and beyond. Devoret and Schoelkopf (p. [1169][3]) speculate on the future of superconducting circuits, whereas Awschalom et al. (p. [1174][4]) focus on the many promising qubit flavors based on spins in semiconductors. Finally, Stern and Lindner (p. [1179][5]) lay out the prospects for quantum computation using the entirely different approach of topologically protected states.
The future of QIP appears bright in spite of the many remaining challenges. As a bonus, overcoming these challenges will probably also advance basic research.
[1]: pending:yes
[2]: /lookup/volpage/339/1164?iss=6124
[3]: /lookup/volpage/339/1169?iss=6124
[4]: /lookup/volpage/339/1174?iss=6124
[5]: /lookup/volpage/339/1179?iss=6124
The development of quantum mechanics and quantum physics in general is one of the greatest intellectual achievements of the 20th century. Initially, quantum physicists focused on mathematically describing and understanding the laws of a micro-world, comprised of atoms, molecules and photons. Nuclei and sub-atomic particles were discovered, particle physics evolved, and complex quantum systems in chemistry and solid-state physics are now described in terms of quantum physics. Within a century, quantum physics became the framework, which allows us to describe and predict, albeit with probabilities, the behavior of the microscopic world as we know it. The powerful quantum framework led to revolutionary technical advances for a century, such as semiconductor technology and the entire electronics industry based on it, enabling computers and the information age. The development of lasers found applications in many areas of our current technologies; we use them for printers, storing and retrieving information using CDs, industrial welding, medical surgery, and for range finding and communication purposes. Medical imaging using MRI is now a routine instrument, as are precision measurements using tunneling and atomic force microscopes. Superconducting technologies are used for high magnetic fields and many more current technologies are based on and enabled by the laws of quantum physics. While the framework of quantum physics has thus proven to be extremely successful and powerful, throughout the last century there were many conceptual, and to some extent philosophical, discussions on our understanding of quantum physics. As early as the 1930s, Einstein and Schrödinger realized that quantum physics allows for some peculiar states, which Schrödinger called “entangled”, which have a non-local character and thus do find an easy interpretation in our classical world. It took a few more decades until John Bell conceived a way to quantify such states, which thus became amenable to measurements. Only in the eighties and nineties of the last century did the generation of entangled states, their characterization and their subsequent application become feasible and accessible in laboratories. Early on, Bell states were proposed for applications in quantum communication, employing protocols based on teleportation. Soon, entanglement was recognized to be useful also for sensing, for precision measurements and eventually for quantum information processing. Starting with the early concept of a trapped-ion quantum computer introduced by Ignacio Cirac and Peter Zoller in 1995, many other platforms were proposed for quantum information processing, based on superconducting quantum bits, photonic processes, engineered quantum dots and many more. The first decade of the 21st century saw an explosive development of quantum information physics, which is by now a mature field and increasingly focuses on applications. Worldwide efforts are ongoing to realize quantum networks for secure communication and to implement quantum computers. Enhanced sensing has been demonstrated using advanced quantum states, and quantum simulators have been developed, already tackling problems that are hard to compute with classical computers. While architectures for full-fledged quantum computers are already available, the realization of such computers still requires the routine implementation of error correction, which is not yet available, for full scalability. Currently, noisy intermediate-scale quantum (NISQ) processors are already used for computations and are even accessible via cloud services. Since about 2000, quantum technologies have been developed for many platforms with the aim to surpass the capablities of their classical counterparts. Many such devices now make use of entangled states, which are seen as the new resource for advanced quantum technologies. For this, describing, understanding and generally mastering the generation and manipulation of entanglement is a key element. Moreover, both hardware and software technologies have to be improved in order to better control quantum devices. Mastering quantum phenomena for communication, metrology, simulation and computation purposes is currently one of the hottest topics in science since the wide applicability of quantum technologies will revolutionize these fields. The development of advanced quantum technologies is thus seen worldwide as a strategic area for generating technical knowledge and industrial evolution. This special issue intends to showcase the breadth and impact of the ongoing research in advancing quantum technologies. We have invited a selection of renowned scientists to present their work, and we are confident that this issue will find a broad readership and attract much interest within the scientific community.
In the twentieth century, quantum physics is one of the most successful approaches in scientific progress. To theorize the concept of quantum computing Max Planck's idea of the existence of energy in individual units like matter was used. Since then, the idea of manufacturing quantum computers for everyday use is becoming more plausible with technological advances in quantum theory. A classical computer carries out logical operations using a bit which is either 1 or 0. In contrast to a classical computer, a quantum computer works with a quantum bit or qubit, which is not limited to two states only. Qubits can exist in a superposition of the two states creating parallelism. Qubit represents the state of atoms, ions, photons or electrons. These qubits which work together with a control device act as a computer memory.Quantum computers have the potential to become million times more potent than present-day supercomputers due to the presence of these multiple states simultaneously. Concepts and ideas of quantum computing have been demonstrated by different methods like Ion Trap, Quantum Dot methods etc. However, the actual realization of such a superior system is still in the future. A strategy must be formulated to maintain decoherence and other potential sources of error at a permissible level.Astonishingly, quantum computing took a long time to take off, even though the physicists have known about the world of subatomic particles. Even so, it took computer scientists another half-century to consider harnessing quantum effects for computation. Also, it was later discovered that quantum computers could solve quantum mechanical many-body problems that are impractical to solve on a classical computer. The foundations of the subject of quantum computation may have become well-published, but the knowledge is still growing. Hence here is a research paper based on the study of quantum computation.
The XXVIth International Conference on Photonic, Electronic and Atomic Collisions was held on the campus of Western Michigan University (WMU) in Kalamazoo during 22–28 July 2009. Kalamazoo, the home of a major state university amid pleasant surroundings, was a delightful place for the conference. The 473 scientific participants, 111 of whom were students, had many fruitful discussions and exchanges that contributed to the success of the conference. Participants from 43 countries made the conference truly international in scope. The 590 abstracts that were presented on the first four days formed the heart of the conference and provided ample opportunity for discussion. This change, allowing the conference to end with invited talks, was a departure from the format used at previous ICPEAC gatherings in which the conferences ended with a poster session. The abstracts were split almost equally between the three main conference areas, i.e., photonic, electronic, and atomic collisions, and the posters were distributed across the days of the conference so that approximately equal numbers of abstracts in the different areas were scheduled for each day. Of the total number of presented abstracts, 517 of these are included in this proceedings volume, the first time that abstracts have been published by ICPEAC. There were 5 plenary lectures covering the different areas of the conference: Paul Corkum (University of Ottawa) talked on attosecond physics with atoms and molecules, Serge Haroche (Collège de France) on non-destructive photon counting, Toshiyuki Azuma (Tokyo Metropolitan University) on resonant coherent excitation of highly-charged ions in crystals, Eva Lindroth (Stockholm University) on atomic structure effects, and Alfred Müller (Justus Liebig University) on resonance phenomena in electron- and photon-ion collisions. Two speakers gave very illuminating public lectures that drew many people from the local area, as well as conference participants: Patricia Dehmer (US DOE) gave a talk on 'Facing Our Energy Challenges in a New Era of Science' and William Phillips (Nobel laureate, NIST) presented a talk on 'Time, Einstein, and the Coolest Stuff in the Universe'. These public talks, held on Thursday and Friday evenings, respectively, were very accessible to a general audience. In addition, there were 61 progress reports on ongoing current research, and 26 special reports selected from the submitted abstracts based on their relevance and importance. These talks covered the full range of the conference topics. Notably, this was the 50th anniversary of ICPEAC and a formal session was held the first day to honor the event as well as those who were instrumental in initiating the conference. Thirteen scientists, representing both those from the early days of ICPEAC as well as chairs of previous ICPEACs, were present and called to the stage, including Benjamin Bederson, Lewis Branscomb, Robert Crompton, Alexander Dalgarno, Gordon Dunn, Werner Eissner, Brian Gilbody, Edward Gerjuoy, Hartmut Hotop, Eugen Merzbacher, Eugene Rudd, Felix Smith, and Aaron Temkin. Steven Manson was the chair of the session and he introduced those present from the early days. Joachim Burgdörfer presented an overview of the history of ICPEAC. This session was followed by a special anniversary reception to honor all of the early 'ICPEACers'. Generous support for the conference was provided by IUPAP, the WMU President's office, and the National Science Foundation. The funds were sizeable, timely, and greatly appreciated, and permitted us to support a significant number of young scientists (postdocs and students) and persons from developing/disadvantaged countries. Nevertheless, the number of requests was far greater than the total support available (by about a factor of five!), and we had to turn down many financial requests. We encourage the organizers of the next ICPEAC to seek a higher level of funding for supporting young scientists and scientists from developing/disadvantaged countries. All in all, the XXVIth ICPEAC in Kalamazoo was very successful. The plenary lectures and the progress and special reports bridged the gap between the different fields of collision physics, making it possible for non-experts in a given area to gain insight into new areas. Also, included among the speakers were several young scientists, namely, postdocs and students, who brought new perspectives to their fields. The next ICPEAC will take place in Belfast in 2011, and the ones after that will be in Lanzhou in 2013 and Madrid in 2015. Given the rapidity with which science is advancing in all of the areas covered by ICPEAC, we expect that these future ICPEAC conferences will be as stimulating as this most recent one was, as indicated by the contributions presented in this proceedings volume. Ann Orel, University of California-Davis Anthony F Starace, University of Nebraska-Lincoln Dragan Nikolić, Western Michigan University Nora Berrah, Western Michigan University Thomas W Gorczyca, Western Michigan University Emanuel Y Kamber, Western Michigan University John A Tanis, Western Michigan University The PDF file contains details of the Sponsors and Exhibitors, Committees and Previous Proceedings.
This year in October the Humboldt Foundation invited its award winners, fellows, alumni, top league scientists and young researchers to discuss problems and successes in quantum optics. It was the third Humboldt Award Winners‘ Forum held in Bonn from 9–12 October. The first one “Frontiers in Macromolecular and Material Science” was held in 2011, followed by “The New Desire for Metaphysics” the year after. This year, about 180 participants from all over the world attended the forum “Frontiers in Quantum Optics: Taming the World of Atoms and Photons – 100 Years after Niels Bohr” which took place at the Hotel Bristol and, partly, at the University of Bonn, Germany. Jürgen Fohrmann, rector of the university in Bonn, opened the conference with his welcome address, followed by Jürgen Nimptsch, the Lord Mayor of the City of Bonn, and Helmut Schwarz, President of the Alexander von Humboldt Foundation. The first keynote lecture was given by Serge Haroche (Collège de France, Paris) titled “Controlling photons in a box to explore the quantum world”. His talk outlined his Nobel Prize winning work and new developments (see Fig. 1).1 The next day (Thursday, 10), further welcome and introduction speeches were given by Enno Aufderheide, Secretary General of the Alexander von Humboldt Foundation, Wolfgang Sandner, Vice-President of the Deutsche Physikalische Gesellschaft, and Dieter Meschede from the University Bonn who organized the meeting. The forum was organized in four panels. The first one “Exploring the Quantum World with Atoms and Photons” was introduced and chaired by Jean-Michel Raimond. Howard J. Carmichael held a keynote lecture about 100 years of quantum jumps, outlining the history from Bohr and Einstein's A and B coefficients to the works by Haroche's group and beyond. Vahid Sandoghdar talked about the efficient coupling of single photons and single quantum emitters in a cavity-free way, Nir Davidson continued the session by talking about long coherence times in dense ultracold atomic ensembles, and Atac Imamoglu finished the session by outlining recent developments in solid-state quantum optics. The panel “Cold Atoms and Many Body Physics” was chaired by Wolfgang Ketterle who also introduced the topic in a brief presentation. Ketterle showed how physics is interconnected and that the study of cold atoms can indeed help solving problems in many-body (solid-state) physics. There is a quest for new materials, like high-temperature superconductors, new carbon-based materials (e.g. nanotubes or graphene) or materials revealing colossal magnetoresistance, to name just a few. There will be more materials needed in the future. To newly discover or to further understand these materials “we like to use paradigmatic models”, he said, “some sort of atomic ‘legos’ that help us understand complex systems”. We are now in a process of quantum “engineering” that will most likely guide future progress in the field. The following lectures further outlined this vision. Georgii V. Shlyapnikov talked about many-body physics of quantum gases in disorder. Of special interest was his discussion about work based on D.M. Basko, I.L. Aleiner, B.L. Altshuler (the AAH model) in which fluid–insulator transitions of disordered quantum gases were discussed. In these systems a surprising effect can occur. Shlyapnikov said: “Imagine you boil a pot of water and then discover that you got ice cubes as a result”, i.e. phase transitions can occur that are unique and do not appear in other systems or materials. Massimo Inguscio continued the session with a discussion about ultracold fermions and novel one-dimensional matter, and Michael Köhl talked about photonic coupling of atoms and solid-state quantum systems, asking the question “Can we make different quantum systems communicate with each other?” – a theme that will keep many scientists busy over the next few years or decades. Finally, Tilman Pfau showed the potential of using electrons of Rydberg atoms to probe Bose–Einstein condensates (BEC). As he showed, the electrons of Rydberg atoms with very high principal quantum numbers (e.g. around n = 100 to 200) can enclose up to several thousand atoms of a Bose–Einstein condensate – a remarkable achievement which allows the investigation of electron–phonon scattering in the BEC. After a full day of science William A. Kinderman gave a lecture on Ludwig van Beethoven's 1823 composed Diabelli variations and completed his presentation with a first-class performance of the piano sonata in C minor, Opus 111, at the Beethovenhaus in Bonn. The next day (Friday, 11) started with the panel “Quantum Information Science”, which was introduced and chaired by Michael Fleischhauer. Arno Rauschenbeutel talked about the possibilities to trap and investigate ions using an optical nanofiber, a technique that has potential as a quantum memory and processing device for quantum computing. Jian-Wei Pan discussed recent experimental progress in quantum manipulation with photons and cold atoms, specifically in quantum information processing (QIP). He showed that linear system equations of the form ; can be solved faster using QIP (with O(log(N)) steps) than in a classical way (with O(N) steps), but that the scalability of QIP is still a challenge as it requires quantum repeaters and quantum memories. He also showed the latest achievements in long-range free-space quantum communication of around 100 km in China and other places and noted that the next step would be to cover a 1200-km distance via satellite. The ultimate aim is to enable and set up large-scale, long-range quantum communication networks. Andrea Alberti discussed transport phenomena in quantum systems. Using quantum walks with neutral atoms as an example he showed that classical and quantum systems differ strongly in their behavior. The last session contribution was by David DiVincenzo talking about prospects for superconducting qubits including some outlook for “Moore's law” of coherence times, and surface code error correction using resonators or cavities. Elisabeth Giacobino then introduced the panel “Precision Measurements and Hot Topics”, with keynote lecturer Jun Ye talking about probing exotic quantum matter (e.g. many-body quantum spin dynamics in which quantum fluctuations become correlated) with clock precision. Edward A. Hinds discussed how cold atoms can be used to test fundamental physics, and Gerald Gabrielse continued in this direction with his talk about measured and calculated properties of elementary particles. For example: Is there an electron electric dipole moment? According to the current standard model it is nearly nonexistent (around ). Gabrielse and his coworkers want to challenge this by going beyond the current experimental limit of by one or more orders of magnitude. A positive result would have tremendous effect on the standard model and could help to decide on recent predictions by supersymmetric and technicolor models. Quantum optomechanics on various scales, from nano- to macromechanics was discussed by Markus Aspelmeyer. He also showed that this research field has potential to make contributions at the absolute limit of the physical realm, testing fundamental physical aspects where quantum and space–time (i.e. gravity) aspects become relevant. In the evening, Hans Bachor (Australian National University, Wamboin) gave the dinner speech, or what he called “the after soup” speech as he was placed between the starter and the main course. Among other things, Bachor recalled how science was done in the early times of quantum mechanics and pointed to the central role of personal relationships and friendships among scientists. Bohr was put forward as a memorable example who brought forward many of the central ideas of quantum mechanics by walking and discussing matters with his colleagues, like Heisenberg and Einstein. It is this deep, sometimes controversial, but continuous thinking that enables us to solve sheer insurmountable problems jointly as an interactive science community. The Alexander von Humboldt (AvH) foundation sets great value on promoting excellent scientists, but it does not stop with a one-time support. It goes beyond the usual sponsorship by continued fostering of its award winners, fellows and alumni. It is the networking aspect that makes the foundation a key player in Germany's scientific landscape and unique among international science founders. Steffan Mehlich (AvH representative) emphasized that the family aspect of the Alexander von Humboldt foundation is key to its success and helps strengthen the links within the network. Consequently, the forum did not end with the scientific talks but continued with a cultural program. Here, the participants could visit the castle “Burg Satzvey”, the Radio Telescope Effelsberg at Bad Münstereifel-Effelsberg (Max Planck Institute for Radio Astronomy), and the winery “Kloster Marienthal” (Bad Neuenahr), thus getting into closer contact with each other. Helmut Schwarz formulated it at the beginning of the meeting: “Science is made by individuals, not by projects”. In the end it needs both – individuals and projects – but the meeting showed that without a strong focus on the researcher as a person there will be no progress. This meeting was in the right spirit to bring together outstanding individuals and to make them think and work together.