This paper briefly comments on the current state of quantum optics. This volume contains some papers related to the 17th Central European Workshop on Quantum Optics in St Andrews, Scotland. Apparently, the notion of Central Europe has moved—the Scottish coast traditionally belongs to the north of Western Europe and St Andrews has been the end of the world by definition1. Has quantum optics moved as well? Clearly, modern trends such as quantum communication or experiments with ultracold atoms were nearly unthinkable when quantum optics began as a research area in the 1950s. Quantum optics began in astronomy with the Hanbury–Brown–Twiss experiment [1] where the statistics of thermal photons was used to measure the size of stars. These days, we discuss Hanbury–Brown–Twiss correlations in ultracold atoms [2]. Quantum optics has always been inspired by the foundations of quantum mechanics, by our attempts to make sense of quantum weirdness. In recent times, quantum information scientists managed to extract substantial funds for research on quantum weirdness that fueled a renaissance in the study of the foundations of quantum mechanics. Some of the ultramodern trends such as connections between quantum optics and general relativity [3] or the enigma of the momentum of light in media [4] date back to the beginning of the 20th century [5–7]. It seems that the further we go into the future the farther we go back in the past. Is this good or bad? Remember the saying that if you write a book about a subject that has been around for a century your book may last 1 According to an ancient legend, St Andrews was founded by the Greek monk St Regulus who, following divine command, brought the relics of the apostle Saint Andrew to the end of the world. for a century, if the subject is a decade old, the book may last a decade, if it is last year’s news . . . . No matter where Central Europe is going to be for the next workshops, quantum optics will be with us.
This paper briefly comments on the current state of quantum optics. This volume contains some papers related to the 17th Central European Workshop on Quantum Optics in St Andrews, Scotland. Apparently, the notion of Central Europe has moved—the Scottish coast traditionally belongs to the north of Western Europe and St Andrews has been the end of the world by definition1. Has quantum optics moved as well? Clearly, modern trends such as quantum communication or experiments with ultracold atoms were nearly unthinkable when quantum optics began as a research area in the 1950s. Quantum optics began in astronomy with the Hanbury–Brown–Twiss experiment [1] where the statistics of thermal photons was used to measure the size of stars. These days, we discuss Hanbury–Brown–Twiss correlations in ultracold atoms [2]. Quantum optics has always been inspired by the foundations of quantum mechanics, by our attempts to make sense of quantum weirdness. In recent times, quantum information scientists managed to extract substantial funds for research on quantum weirdness that fueled a renaissance in the study of the foundations of quantum mechanics. Some of the ultramodern trends such as connections between quantum optics and general relativity [3] or the enigma of the momentum of light in media [4] date back to the beginning of the 20th century [5–7]. It seems that the further we go into the future the farther we go back in the past. Is this good or bad? Remember the saying that if you write a book about a subject that has been around for a century your book may last 1 According to an ancient legend, St Andrews was founded by the Greek monk St Regulus who, following divine command, brought the relics of the apostle Saint Andrew to the end of the world. for a century, if the subject is a decade old, the book may last a decade, if it is last year’s news . . . . No matter where Central Europe is going to be for the next workshops, quantum optics will be with us.
Although the origin of quantum optics can be traced back to the beginning of the 20th century, when the fundamental ideas about the quantum nature of the interaction between light and matter were put forward, the splendid blossoming of this part of physics began half a century later, after the invention of masers and lasers. It is remarkable that after another half a century the tree of quantum optics is not only very strong and spreading, but all its branches continue to grow, showing new beautiful blossoms and giving very useful fruits. A reflection of this progress has been the origin and development of the series of annual events called the Central European Workshops on Quantum Optics (CEWQO). They started at the beginning of the 1990s as rather small meetings of physicists from a few countries in central-eastern Europe, but in less than two decades they have transformed into important events, gathering 100 to 200 participants from practically all European countries. Moreover, many specialists from other continents like to attend these meetings, since they provide an excellent chance to hear about the latest results and new directions of research. Regarding this, it seems worth mentioning at least some of the most interesting and important areas of quantum optics that have attracted the attention of researchers for the past two decades. One of these areas is quantum information, which over the course of time has become an almost independent area of quantum physics. But it still maintains very close ties with quantum optics. The specific parts of this area are, in particular, quantum computing, quantum communication and quantum cryptography, and the problem of quantitative description of such genuine quantum phenomena as entanglement is one of the central items in the current stream of publications. Theory and experiment related to quantum tomography have also become important to contemporary quantum optics. They are closely related to the subject of so-called quantum-state engineering. Different schemes proposed within the framework of this new area enabled the creation in laboratories of various superpositions of quantum states which had previously existed only as beautiful mathematical constructions by theoreticians. Connected to this, recent experiments related to such old problems as decoherence and quantum–classical transition are quite impressive. The same can be said about the interrelations between quantum optics and physics of ultracold atoms and Bose–Einstein condensates. Great progress has been made in cavity quantum electrodynamics, and the past decade gave rise to the new area of circuit quantum electrodynamics. Nowadays, we are very close to the observation of the quantum behavior of macroscopic bodies (mirrors), and the methods used in quantum optics help to achieve this goal. Quantum optics over the past two decades has resulted in such impressive discoveries as the slowing down of light to extremely low velocities and the creation of photonic crystals. The new methods of achieving very strong coupling coefficients between quantized field modes and atomic degrees of freedom open new possibilities for storing and retrieving quantum information transmitted by light. New areas of terahertz, femto- and atto-second optics were born or were significantly developed during the past two decades. In addition, the tomographic-probability representation of photon-quantum states has created new possibilities both in theoretical and experimental aspects of quantum optics. Traditionally, measured optical tomograms of photon states were considered as a technical tool for reconstructing the Wigner functions of quantum states. It became clear that these measured tomograms are primary objects; one does not need to reconstruct the Wigner function to extract information on physical properties of the state, for example, on the state purity. Purity is experimentally obtained directly from measured optical tomograms of photon states. The uncertainty relations for photon quadratures were also checked for the thermal photon state using experimental values of optical tomograms and avoiding the reconstruction procedure of the Wigner function and its associated precision constrains. In the tomographic-probability representation of quantum mechanics and quantum optics, tomograms are used for the description of quantum states as an alternative to the wave function and density matrix. The purity, fidelity, entropy and photon temperature associated with quantum states are expressed in terms of tomograms. This provides the possibility of measuring these characteristics directly by taking optical tomograms and checking basic inequalities like entropic uncertainty relations, temperature-dependent quadrature uncertainty relations, etc. The better understanding that quantum states can be identified with measurable probability distributions like optical tomograms opens new prospects in quantum optics, for example, to check experimentally the uncertainty relations for higher quadrature momenta and to control the precision with which the fundamental inequalities of quantum mechanics are experimentally confirmed. This Topical Issue is a collection of papers presented at the 17th Central European Workshops on Quantum Optics (CEWQO10) held at the University of St Andrews, Scotland, UK, 6–11 June 2010. The other collaborators from different scientific centers who could not, due to different reasons, come to St Andrews but participated in the previous CEWQOs and plan to participate in future CEWQOs also contributed to this issue. The paper by Ulf Leonhardt and Natalia Korolkova, the CEWQO10 Organizers, opens this issue. The order of the following papers corresponds to the alphabetical order of the first author of the paper. The history of CEWQOs can be found in the Preface to the Proceedings of the 15th CEWQO (2009 Phys. Scr. T135 011005 ). The Proceedings of the 16th Central European Workshop on Quantum Optics (CEWQO09), held at the University of Turku, are also available (2010 Phys. Scr. T140 ). The 18th Central European Workshop on Quantum Optics (CEWQO11) will be held in Madrid, Spain on 30 May--3 June 2011. It will be chaired by Professor Luis Lorenzo Sanchez Soto from the Complutense University of Madrid. List of Papers The 17th Central European Workshop on Quantum Optics in St Andrews, Scotland Ulf Leonhardt and Natalia Korolkova Double self-Kerr scheme for optical Schrödinger-cat state preparation P Adam, Z Darázs, T Kiss and M Mechler Relations between scaling transformed Husimi functions, Wigner functions and symplectic tomograms describing corresponding physical states V A Andreev, D M Davidović, L D Davidović and M D Davidović Entanglement dynamics of two independent cavity-embedded quantum dots B Bellomo, G Compagno, R Lo Franco, A Ridolfo and S Savasta Dynamical stabilization of spin systems in time-dependent magnetic fields Yu V Bezvershenko, P I Holod and A Messina Entanglement dynamics of a bipartite system in squeezed vacuum reservoirs Smail Bougouffa and Awatif Hindi On Wheeler's delayed-choice Gedankenexperiment and its laboratory realization M Božić, L Vušković, M Davidović and Á S Sanz A smooth, holographically generated ring trap for the investigation of superfluidity in ultracold atoms Graham D Bruce, James Mayoh, Giuseppe Smirne, Lara Torralbo-Campo and Donatella Cassettari Parametric amplification of the classical field in cavities with photoexcited semiconductors V V Dodonov Mutually unbiased bases: tomography of spin states and the star-product scheme S N Filippov and V I Man'ko Quantum trajectory model for photon detectors and optoelectronic devices Teppo Häyrynen, Jani Oksanen and Jukka Tulkki Entanglement in two-mode continuous variable open quantum systems Aurelian Isar A classical field comeback? The classical field viewpoint on triparticle entanglement Andrei Khrennikov Experimental investigation of the enhancement factor and the cross-correlation function for graphs with and without time-reversal symmetry: the open system case Michał Ławniczak, Szymon Bauch, Oleh Hul and Leszek Sirko Independent nonclassical tests for states and measurements in the same experiment Alfredo Luis and Ángel Rivas On the classical capacity of quantum Gaussian channels Cosmo Lupo, Stefano Pirandola, Paolo Aniello and Stefano Mancini Entropic inequalities for center-of-mass tomograms Margarita A Man'ko Semiclassical dynamics for an ion confined within a nonlinear electromagnetic trap Bogdan M Mihalcea Zeno-like phenomena in STIRAP processes B Militello, M Scala, A Messina and N V Vitanov A beam splitter with second-order nonlinearity modeled as a nonlinear coupler V Peřinová, A Lukš and J Křepelka Energy-level shifts of a uniformly accelerated atom between two reflecting plates L Rizzuto and S Spagnolo Cross-Kerr nonlinearities in an optically dressed periodic medium K Słowik, A Raczyński, J Zaremba, S Zielińska-Kaniasty, M Artoni and G C La Rocca An approximate effective beamsplitter interaction between light and atomic ensembles Richard Tatham, David Menzies and Natalia Korolkova Stochastic simulation of long-time nonadiabatic dynamics Daniel A Uken, Alessandro Sergi and Francesco Petruccione
The series of Central European Workshops on Quantum Optics looks back on a successful annual sequence of ten meetings, previously held at locations in Slovakia, Hungary, the Czech Republic, and most recently in Germany. The goal to provide a forum for quantum optics specialists from both Central Europe and elsewhere has always been accompanied by an attempt to provide a small-sized and affordable meeting. Together with the contributions of the participants and the many discussion during the meetings, the special flair of this series of Workshops has become well established. This special issue of Journal of Optics B: Quantum and Semiclassical Optics is devoted to the tenth anniversary Workshop, held during 4–7th April 2003 at Rostock-Warnemünde, Germany, on the coast of the Baltic Sea. It contains selected articles by the participants of the Workshop, who came not only from Central Europe but also from other parts of the world. Their contributions cover a variety of subjects, reflecting the fact that, stimulated by the progress of experimental techniques, quantum optics has become a rapidly growing field of research.
Much of our present understanding of the microscopic world is based on quantum mechanics. The field owes much of its existence to the venerable science of optics, since the fundamental ideas on the nature of the interaction between light and matter lie at the roots of its origin. We have now reached one century of quantum mechanics. In contrast, the splendid blossoming of quantum optics began only after the comparatively recent invention of the laser. Since then, it has become an exciting and always expanding area at the cutting-edge of research, in part because theory and experiment are more closely connected in this field than any other. Moreover, the technological distance between fundamental studies and practical applications has always been very short in quantum optics. As a result, modern engineering is increasingly based on quantum rather than classical physics; we are facing a transition similar to the one society confronted 200 years ago, at the start of the Industrial Revolution. In parallel with this, the physics community is witnessing the recent and vigorous emergence of quantum information. It aims at exploring the physical foundations of information and at developing efficient methods for processing quantum information. The questions driving this field reveal a profound change in attitude towards fundamental aspects of quantum theory. The photon turns out to be a tool extremely well suited to exploring theoretical quantum information schemes and their experimental implementations. Mirroring this continued progress has been the growth and development of the series of annual Central European Workshops on Quantum Optics (CEWQO). The series started at the beginning of the 1990s, as rather small meetings of physicists from a few countries in central-eastern Europe. In two decades, the workshops have transformed into important events that reach well beyond the original rather restricted geographical limits. The history of CEWQOs can be found in the preface to the proceedings of the 15th CEWQO ( Physica Scripta 2009 T135 011005 ). The 18th edition of CEWQO (CEWQO11) was held in Madrid in 2011. There were about 250 participants, from practically every European country. Many colleagues from other continents also joined the event, including well-established researchers in the field. This is a clear demonstration that these meetings provide an excellent chance to hear about the latest results and new directions of research. The organization of CEWQO11 was carried out by a committee consisting of members active in this topic in Madrid. From Universidad Complutense, Alberto Galindo and Luis L Sánchez-Soto; from Universidad Autónoma, Jose Calleja and Carlos Tejedor; from Universidad Politécnica, Enrique Calleja; from Universidad Carlos III, Alberto Ibort; and from the National Research Council (CSIC), Juan León and Juan J García-Ripoll. Special thanks go to the Spanish Ministry for Science and Innovation, Universidad Complutense and the Quitemad Consortium for financial support. The proceedings of the 16th CEWQO held at the University of Turku, Finland and the 17th CEWQO held at the University of St Andrews, Scotland, UK are also available ( Physica Scripta 2010 T140 and Physica Scripta 2011 T143 ). The present Topical Issue is a collection of papers presented in Madrid; they represent an illustrative sample of the major achievements and trends in this area. In turn, they reflect the wide range of interests in this rapidly evolving field. Some collaborators from different scientific centres who could not, due to different reasons, come to Madrid, but participated in previous CEWQOs and plan to participate in future CEWQOs, also contributed to this issue. The papers are arranged alphabetically by the name of the first author. Special thanks goes to Roger Wäppling, the Managing Editor of Physica Scripta , and Graeme Watt, the Publisher, for the opportunity to publish CEWQO11. From a Physica Scripta Editorial Board meeting it was decided that Physica Scripta could offer a poster prize (200 euros + certificate) for young scientists (less than 30 years old) at the annual CEWQO conference. A panel of experts was formed to judge the posters which included Apostol Vourdas, University of Bradford, UK (Chairman), Alberto Ibort, University Carlos III of Madrid, Spain, Andrei Klimov, University of Guadalajara, Mexico, Margarita A Man'ko, P N Lebedev Physical Institute, Moscow, Russia and Antonino Messina, University of Palermo, Italy. The poster ''How can we check the uncertainty relation?'' by Vladimir Chernega, PhD student of the P N Lebedev Physical Institute, won the prize. The 19th Central European Workshop on Quantum Optics will be held in Sinaia, Romania on 2–6 July 2012. It will be chaired by Professor Aurelian Isar from the Horia Hulubei National Institute for Research and Development in Physics and Nuclear Engineering, Bucharest.
The development of quantum optics was part and parcel of the formation of modern physics following the fundamental work of Max Planck and Albert Einstein, which gave rise to quantum mechanics. The possibility of working with pure quantum objects, like single atoms and single photons, has turned quantum optics into the main tool for testing the fundamentals of quantum physics. Thus, despite a long history, quantum optics nowadays remains an extremely important branch of physics. It represents a natural base for the development of advanced technologies, like quantum information processing and quantum computing. Previous Central European Workshops on Quantum Optics (CEWQO) took place in Palermo (2007), Vienna (2006), Ankara (2005), Trieste (2004), Rostock (2003), Szeged (2002), Prague (2001), Balatonfüred (2000), Olomouc (1999), Prague (1997), Budmerice (1995, 1996), Budapest (1994) and Bratislava (1993). Those meetings offered excellent opportunities for the exchange of knowledge and ideas between leading scientists and young researchers in quantum optics, foundations of quantum mechanics, cavity quantum electrodynamics, photonics, atom optics, condensed matter optics, and quantum informatics, etc. The collaborative spirit and tradition of CEWQO were a great inspiration and help to the Institute of Physics, Belgrade, and the Serbian Academy of Sciences and Arts, as the organizers of CEWQO 2008. The 16th CEWQO will take place in 2009 in Turku, Finland, and the 17th CEWQO will be organized in 2010 in St Andrews, United Kingdom. The 15th CEWQO was organized under the auspices and support of the Ministry of Science of the Republic of Serbia, the Serbian Physical Society, the European Physical Society with sponsorship from the University of Belgrade, the Central European Initiative, the FP6 Program of the European Commission under INCO project QUPOM No 026322, the FP7 Program of the European Commission under project NANOCHARM, Europhysics Letters (EPL), The European Physical Journal (EPJ), and John Wiley and Sons.
We are glad to welcome you at the 21st Central European Workshop on Quantum Optics. Started in 1993 in Bratislava within a European project aimed at collaborating with Central-European countries, the Central European Workshops on Quantum Optics have evolved into a central annual gathering of European researchers working in this fast growing field as well as its applications to quantum information sciences and the foundations of quantum mechanics. For two decades, the workshops traveled all over the continent, reaching its geographical edges. This year, the 21st edition comes to the of Europe.We thank all the participants for the abstract submissions. The peer-review has shown a high level of contributions accepted for oral and poster presentations. As usual, we see a substantial participation of students and young postdocs from around the world and we are happy that our field attracts new generations of researchers. CEWQO 2014 in Brussels would have been impossible without the steering of Prof. Antonino Messina and Prof. Margarita Man'ko,who kindly proposed to locate the 21st edition here and provided a priceless help at all stages of its preparation. We would like to acknowledge also the previous organizers of CEWQO workshops for sharing their experience, in particular Prof. Gunnar Bjork and Prof. Aurelian Isar. A valuable help in the selection of invited speakers and in reviewing the contributions was given by the members of the International Advisory Board.We have received financial support from the Brussels Capital Region via its agency VISITBRUSSELS, the two National Research Funds, F.R.S.-FNRS and FWO, the Interuniversity Attraction Poles program of the Belgian Science Policy Office (BELSPO) via project Photonics@be,and the European program CHIST-ERA via projects HIPERCOM and QSCALE.Among our sponsors are the European Physical Society (via the journal EuroPhysics Letters) which supported student grants, the American Institute of Publishing (via Physica Scripta) which offered the Best Poster Award for young scientists, and Springer Publishing (via The European Physical Journal) which contributed to the organization of a plenary session, along with the company IDQ.We would like to thank all members of the local organizing committee and our colleagues, who invested their time for making this conference happen.
More than a century after the beginning of the quantum revolution, historians continue to explore new facets in the history of quantum physics, and to re-examine some of its better-known aspects. The thirteen papers collected in this volume, by authors from five continents, present central trends in the current study of quantum physics within its theoretical, experimental, philosophical, technological and social contexts. They discuss developments from the late nineteenth to the early twenty-first century and go beyond the traditional focus on Europe and North America to include China and Japan, and beyond the Heisenbergs and Diracs to reveal the role of actors who hitherto have played only a marginal role in historical account, but left their mark on the development of quantum physics. Also a wider array of subdisciplines comes into view, from optics to quantum gravity through quantum electrodynamics, from atomic and nuclear to condense matter physics and foundations of physics. Moreover, the volume shows that fields such as dispersion, physical chemistry and solid state physics should not be seen merely as areas of applications of ideas that evolved in other contexts, but should be regarded as birthplaces of important theoretical insights. The perspective of the papers ranges from local histories to global discussions, from conceptual changes via the role of experimentation to interactions with social and technological forces and to the interpretation of the theory.