Guest Editors: W Lange Max-Planck-Institut für Quantenoptik, Garching, Germany J-M Gerard Laboratoire de Physique des Semiconducteurs, Grenoble, France Cavity QED interactions of light and matter have been investigated in a wide range of systems covering the spectrum from microwaves to optical frequencies, using media as diverse as single atoms and semiconductors. Impressive progress has been achieved technologically as well as conceptually. This topical issue of Journal of Optics B: Quantum and Semiclassical Optics is intended to provide a comprehensive account of the current state of the art of cavity QED by uniting contributions from researchers active across this field. As Guest Editors of this topical issue, we invite manuscripts on current theoretical and experimental work on any aspects of cavity QED. The topics to be covered will include, but are not limited to: •Cavity QED in optical microcavities •Semiconductor cavity QED •Quantum dot cavity QED •Rydberg atoms in microwave cavities •Photonic crystal cavity QED •Microsphere resonators •Microlasers and micromasers •Microdroplets •Dielectric cavity QED •Cavity QED-based quantum information processing •Quantum state engineering in cavities The topical issue is scheduled for publication in February 2004. Manuscripts should be submitted to the Publisher by 31 July 2003, quoting `Topical Issue/Cavity QED', although early submission would be welcomed. All papers will be peer-reviewed in accordance with the normal refereeing procedures and standards of Journal of Optics B: Quantum and Semiclassical Optics . Manuscripts should be prepared according to the general guidelines for authors published in the journal. Electronic submission in LaTeX is welcomed. Full details on how to structure an article, including specific information on figures, tables and references, are available from our Web site at www.iop.org/Journals/authors/jopb . There are no page charges for publication. In addition to the usual 50 free reprints, the corresponding author contributor of each paper published will receive a complimentary copy of the topical issue. We look forward to receiving your contribution to this topical issue. Submission address: Dr Claire Bedrock (Publisher) Journal of Optics B: Quantum and Semiclassical Optics Institute of Physics Publishing Dirac House Temple Back Bristol BS1 6BE UK jopb@iop.org
Guest Editors: W Lange Max-Planck-Institut für Quantenoptik, Garching, Germany J-M Gerard Laboratoire de Physique des Semiconducteurs, Grenoble, France Cavity QED interactions of light and matter have been investigated in a wide range of systems covering the spectrum from microwaves to optical frequencies, using media as diverse as single atoms and semiconductors. Impressive progress has been achieved technologically as well as conceptually. This topical issue of Journal of Optics B: Quantum and Semiclassical Optics is intended to provide a comprehensive account of the current state of the art of cavity QED by uniting contributions from researchers active across this field. As Guest Editors of this topical issue, we invite manuscripts on current theoretical and experimental work on any aspects of cavity QED. The topics to be covered will include, but are not limited to: •Cavity QED in optical microcavities •Semiconductor cavity QED •Quantum dot cavity QED •Rydberg atoms in microwave cavities •Photonic crystal cavity QED •Microsphere resonators •Microlasers and micromasers •Microdroplets •Dielectric cavity QED •Cavity QED-based quantum information processing •Quantum state engineering in cavities The topical issue is scheduled for publication in February 2004. Manuscripts should be submitted to the Publisher by 31 July 2003, quoting `Topical Issue/Cavity QED', although early submission would be welcomed. All papers will be peer-reviewed in accordance with the normal refereeing procedures and standards of Journal of Optics B: Quantum and Semiclassical Optics . Manuscripts should be prepared according to the general guidelines for authors published in the journal. Electronic submission in LaTeX is welcomed. Full details on how to structure an article, including specific information on figures, tables and references, are available from our Web site at www.iop.org/Journals/authors/jopb . There are no page charges for publication. In addition to the usual 50 free reprints, the corresponding author contributor of each paper published will receive a complimentary copy of the topical issue. We look forward to receiving your contribution to this topical issue. Submission address: Dr Claire Bedrock (Publisher) Journal of Optics B: Quantum and Semiclassical Optics Institute of Physics Publishing Dirac House Temple Back Bristol BS1 6BE UK jopb@iop.org
A single two-level emitter coupled to a single mode of an electromagnetic resonator constitutes the most fundamental instance of light--matter interaction. Realizations of this type of system are investigated in the field of cavity quantum electrodynamics (cavity QED). Particularly important are schemes in which the coupling is strong enough to exceed the spontaneous emission rate as well as cavity damping. In this case, the coherent exchange of excitation between source and photon is the dominating process, providing the unique possibility to deterministically control the quantum evolution of the system. Great progress has recently been accomplished, technologically as well as conceptually, and the focus section in this issue of Journal of Optics B: Quantum and Semiclassical Optics features five articles highlighting important recent developments in the field. Strong coupling between single atoms and the electromagnetic cavity field have been achieved in two distinct regimes, the optical and the microwave region. The latter is represented by the micromaser, a high-Q microwave cavity pumped by a beam of highly excited Rydberg atoms. It has proved to be an almost ideal system for the generation of non-classical field states. A constraint in these experiments is the fact that the field inside the cavity can only be examined indirectly, by analysing the occupation of atoms leaving the cavity. While only two atomic states were previously identified for this purpose, V A Reshetov shows in his article (pages 119--126) that more information on the field may be extracted by taking advantage of the Zeeman substructure of the atomic levels. In the optical domain of cavity QED, by contrast, the state of the resonator field may be probed directly by measuring the light leaking from the cavity using photodetectors. In order to minimize damping, high-quality cavities must be employed. In most optical experiments these are Fabry--Perot resonators with ultra-high reflectivity mirrors, with losses as low as a few parts per million being state of the art. At the same time, the coupling of atoms and photons is enhanced by reducing the length of the cavity, so that strong coupling conditions are reached. A very attractive application of this type of cavity QED setup is the possibility of exerting control over the quantum dynamics of the system. An impressive example is the implementation of quantum feedback, reported in the paper by W P Smith and L A Orozco (pages 127--134). Using information gained from detecting a single photon escaping from the cavity, active feedback is applied to halt the dynamical evolution of the system. This is the first time active feedback has been used to modify the quantum evolution of a system at the single-photon level. The authors discuss how detunings between the subsystems affect the quantum feedback, an issue particularly relevant for ensembles of atoms with a spread in detuning. Perfect quantum feedback in this case requires the use of additional parameters to control the system. The majority of optical cavity QED experiments performed so far have used as a medium atoms traversing the cavity on random trajectories, such as, for example, thermal atomic beams. In this case, the observation of quantum effects is degraded in two ways. The Doppler effect and the finite transit time lead to line broadening, while the spatial structure of the cavity mode results in atoms in different locations experiencing different coupling with the photonic field. J E Reiner et al (pages 135--142) investigate the impact of these effects on quantum fluctuations in their cavity QED system. In order to overcome line broadening, they have developed a continuous cold atomic beam, extracted from a magneto-optical trap. An even better control of broadening effects and fluctuating coupling strength is provided by trapping the atoms inside the cavity and cooling them to temperatures at which their position spread is smaller than the optical wavelength. Much recent activity has been devoted to developing such an ultimate cavity QED system. A Vukics et al (pages 143--153) present a theoretical proposal for dynamically trapping and cooling atoms inside a cavity. By driving the atoms with a standing wave injected from the side of the cavity and by weakly exciting the cavity field itself, they predict three-dimensional trapping of the atom for periods around 1 second, an extremely long time on the typical scale of cavity QED dynamics. The essential component of their scheme is the interference between the two driving fields, determining the temperature of the particle and the stable trapping positions. In the quest for better confinement of radiation, lately, an appealing alternative to the Fabry--Perot cavity has been investigated -- the optical microsphere resonator. A sphere with a diameter of a few tens of microns, it supports so-called whispering gallery modes near its circumference, for which quality factors up to 10 10 have been measured. In order to exploit the correspondingly low field damping rates for cavity QED, a method must be found to couple atomic or solid state emitters to these modes. S Göotzinger et al (pages 154--158) report the coupling of single nanocrystals on the surface of a microsphere through the evanescent field of the mode. Selective excitation of a single nano-emitter was accomplished with a scanning confocal microscope. The system is a promising candidate for cavity QED with single-quantum emitters. The ability to fully control the quantum dynamics of atoms and light is beginning to spawn early applications. The most notable example is quantum information processing. This requires the coherent manipulation of single-quantum systems, which is ideally provided by cavity QED interaction in the strong-coupling limit. The development of practical devices will be among the principal future tasks for research in the field. This will include physical systems, which have not been covered in this issue, such as semiconductors, quantum dots as emitters, or photonic crystals as resonator structures. Cavity QED is therefore guaranteed to remain a vigorous field in the years to come.
This Special Issue of Journal of Optics B: Quantum and Semiclassical Optics brings together contributions of various researchers working on theoretical and experimental aspects of quantum optics and quantum entanglement. The physics of quantum entangled states, an interdisciplinary field of research involving quantum optics, physics of quantum information and foundations of quantum theory, has been intensively exploited over the last decade in connection with quantum information processing, quantum communication and quantum computing. It was shown that the use of entangled states opens new horizons in such practical fields as cryptography, computing, information transmission, quantum imaging and precision measurements. Essential progress has also been achieved in the area of photon squeezing, generation of nonclassical states, including Schrödinger cats, trapped ions, Bose–Einstein condensates, cavity quantum electrodynamics, the Casimir effect, etc. These results have initiated applications in quantum information and communication, quantum imaging and quantum computing. This special issue is published in connection with the International Conference on Quantum Electronics (IQEC 2002) held on 26 June–1 July 2002, in Moscow, Russia, where the topics of quantum optics, generation and characterization of the entangled states and their applications were discussed in the framework of regular sections on quantum optics, quantum information and quantum computing, and during the special symposium on entangled states. We would like to express our gratitude to both authors and reviewers, for their efforts in preparing and ensuring the high scientific quality of the papers in this special issue. While the issue was in preparation for publication, one of the guest editors, Professor Anatoly Oraevski, suddenly passed away. He was a great scientist, recognized worldwide for his numerous important contributions to nonlinear and quantum optics, and to laser physics. Anatoly was always an enthusiastic advisor, mentor and collaborator. All of us remember numerous positive interactions with him, not only while organizing IQEC 2002 in Moscow last summer, but also throughout the years. He will be missed both for his scientific insight and because he was a good, kind and gentle man. Editing this special issue of Journal of Optics B: Quantum and Semiclassical Optics together with Professor Oraevski was our last joint effort and we would like to pay a tribute to him by dedicating this issue to his memory.
Light has always been the most important carrier of information. Most of the information received by a human is visual. Technological breakthroughs have been made by changing from copper networks to networks based on optical data processing using laser light. In the last fifteen years, however, research has gone much further. We can now generate and control new sources of nonclassical light which are constructed from single atoms in a resonator. The systems for generating this new light are the micromaser in the microwave regime and the microlaser in the optical regime. Fundamental properties as well as possible applications have been investigated in a common European effort within the TMR network Microlasers and Cavity QED . Funded by the European Commission seventeen teams have been working together sharing their knowledge about the fundamental interaction of light with matter. These Focus articles will highlight several important findings of this collaboration. From the selection of papers one can immediately see the wide range of research that has been done in this European project. New quantum effects have been found in the interaction of a single light mode with single atoms and new properties of the corresponding field states have been explored. The fundamental forces acting on atoms in a cavity field have been simulated. This will open new ways to cool an ensemble of atoms in a cavity. In addition it has been shown that cold atoms can be transported in a waveguide. Regarding semiconductor microlasers the quantum noise of vertical surface emitting lasers (VCSELs) has been understood experimentally as well as theoretically. The focus articles also demonstrate that the ability to manipulate quantum characteristics of light will have direct applications in information technology. Systems based on cavity QED are candidates for future processing of quantum information. One of the most challenging tasks therefore is to understand the dissipative effects and to actively control the decay of atomic states. A clear understanding of all these decoherence effects then allows for the development of error avoiding quantum codes that stabilize quantum algorithms within the realm of cavity QED. At this point we take the opportunity to thank the authors and the reviewers of these articles for preparing and ensuring high-quality presentations. We are convinced that this cluster of articles will give the readers a broad insight into an inspiring piece of modern physics. Focus on Microlaser and Cavity QED Contents Coherent states sometimes look like squeezed states and vice versa: the Paul trap Michael Martin Nieto and D Rodney Truax Error avoiding quantum codes and dynamical stabilization of Grover's algorithm Michael Mussinger, Aldo Delgado and Gernot Alber Schrödinger-cat entangled state reconstruction in the Penning trap Michol Massini, Mauro Fortunato, Stefano Mancini, Paolo Tombesi and David Vitali Nonlocality of the Schrödinger cat Krzysztof Wódkiewicz Driving atoms into decoherence-free states Almut Beige, Daniel Braun and Peter L Knight Transport of cold atoms in a miniature guide M Key, W Rooijakkers and E A Hinds Quantum noise in VCSELs J-P Hermier, I Maurin, E Giacobino, P Schnitzer, R Michalzik, K J Ebeling, A Bramati and A Z Khoury A physical explanation of excess quantum noise due to non-orthogonal modes A M van der Lee, M P van Exter, N J van Druten and J P Woerdman Collective light forces on atoms in a high-finesse cavity T Fischer, P Maunz, T Puppe, P W H Pinkse and G Rempe Tunable whispering gallery modes for spectroscopy and CQED experiments Wolf von Klitzing, Romain Long, Vladimir S Ilchenko, Jean Hare and Valérie Lefèvre-Seguin Matthias Freyberger and Wolfgang Schleich Abteilung für Quantenphysik, Universität Ulm, Germany
This Special Issue of Journal of Optics B: Quantum and Semiclassical Optics brings together the contributions of various researchers working on theoretical and experimental aspects of fluctuational phenomena in photonics and quantum optics. The topics discussed in this issue extend from fundamental physics to applications of noise and fluctuational methods from quantum to classical systems, and include: • Quantum measurement • Quantum squeezing • Solitons and fibres • Gravitational wave inferometers • Fluorescence phenomena • Cavity QED • Photon statistics • Noise in lasers and laser systems • Quantum computing and information • Quantum lithography • Teleportation.
In this paper, exciting progress of quantum optics in solid state is reviewed. The focus is on semiconductor microcavities with self-assembled quantum dots embedded in the active layer. Due to enormous progress in semiconductor nanotechnology, such photonic structures have become a model system for the study of quantum optics on a scalable and integrable technology platform with high potential for future applications in quantum information technology. Quantum optical phenomena have become accessible due to 3-D confinement of light and matter on the length scale of their wavelength in state-of-the-art semiconductor micro- and nanostructures. This confinement leads to a quantization of the associated photonic and electronic energy levels and requires a quantum mechanical description of the system in the framework of cavity quantum electrodynamics (cQED). This approach considers the dipole interaction between two-level quantum emitters and discrete photonic states of a microcavity. Within the well-known Jaynes-Cummings model, the dipole interaction is described in terms of a coherent exchange of energy between the emitter and the resonator mode. This coherent interaction in the so-called strong coupling regime of cQED is reflected in a normal mode splitting, the vacuum Rabi splitting, of the involved modes and represents a central feature of quantum optics in solid state. Another important example of quantum optics in semiconductor nanostructures is the generation of nonclassical light in specific quantum devices. Of particular interest is the realization of Fock states which represent states containing a well-defined number of photons. Single-photon sources, for instance, allow for the generation of single photons on demand, which is highly desirable for quantum communication systems. In this context, this review paper will present recent experimental studies of quantum optics in solid state. This paper is meant for readers who would like to become familiar with this topic and for experts being interested in the progress in this field. It will cover a broad range of studies ranging from examples of fundamental light-matter interaction in the quantum limit to devices capable of emitting single photons and entangled photon pairs on demand.
The physics of strong light-matter coupling has been addressed in different scientific communities over the last three decades. Since the early eighties, atoms coupled to optical and microwave cavities have led to pioneering demonstrations of cavity quantum electrodynamics, Gedanken experiments, and building blocks for quantum information processing, for which the Nobel Prize in Physics was awarded in 2012. In the framework of semiconducting devices, strong coupling has allowed investigations into the physics of Bose gases in solid-state environments, and the latter holds promise for exploiting light-matter interaction at the single-photon level in scalable architectures. More recently, impressive developments in the so-called superconducting circuit QED have opened another fundamental playground to revisit cavity quantum electrodynamics for practical and fundamental purposes. This book aims at developing the necessary interface between these communities, by providing future researchers with a robust conceptual, theoretical and experimental basis on strong light-matter coupling, both in the classical and in the quantum regimes. In addition, the emphasis is on new forefront research topics currently developed around the physics of strong light-matter interaction in the atomic and solid-state scenarios.