The application of quantum mechanics to information related fields such as communication, computation and cryptography is a fast growing line of research that has been witnessing an outburst of theoretical and experimental results, with possible practical applications. On the one hand, quantum cryptography with its impact on secrecy of transmission is having its first important actual implementations; on the other hand, the recent advances in quantum optics, ion trapping, BEC manipulation, spin and quantum dot technologies allow us to put to direct test a great deal of theoretical ideas and results. These achievements have stimulated a reborn interest in various aspects of quantum mechanics, creating a unique interplay between physics, both theoretical and experimental, mathematics, information theory and computer science. In view of all these developments, it appeared timely to organize a meeting where graduate students and young researchers could be exposed to the fundamentals of the theory, while senior experts could exchange their latest results. The activity was structured as a school followed by a workshop, and took place at The Abdus Salam International Center for Theoretical Physics (ICTP) and The International School for Advanced Studies (SISSA) in Trieste, Italy, from 12–23 June 2006. The meeting was part of the activity of the Joint European Master Curriculum Development Programme in Quantum Information, Communication, Cryptography and Computation, involving the Universities of Cergy–Pontoise (France), Chania (Greece), Leuven (Belgium), Rennes1 (France) and Trieste (Italy). This special issue of Journal of Physics A: Mathematical and Theoretical collects 22 contributions from well known experts who took part in the workshop. They summarize the present day status of the research in the manifold aspects of quantum information. The issue is opened by two review articles, the first by G Adesso and F Illuminati discussing entanglement in continuous variable systems, the second by T Prosen, discussing chaos and complexity in quantum systems. Both topics have theoretical as well as experimental relevance and are likely to witness a fast growing development in the near future. The remaining contributions present more specific and very recent results. They involve the study of the structure of quantum states and their estimation (B Baumgartner et al , C King et al , S Olivares et al , D Petz et al and W van Dam et al ), of entanglement generation and its quantification (G Brida et al , F Ciccarello et al , G Costantini et al , O Romero-Isart et al , D Rossini et al , A Serafini et al and D Vitali et al ), of randomness related effects on entanglement behaviour (I Akhalwaya et al , O Dahlsten et al and L Viola et al ), and of abstract and applied aspects of quantum computation and communication (K Audenart, G M D'Ariano et al , N Datta et al , L C Kwek et al and M Nathanson et al ). We would like to express our gratitude to the European Commission, the Abdus Salam ICTP, SISSA and Eurotech SpA (Amaro, Udine, Italy) for financial and/or logistic support. Special thanks also go to the workshop secretary Marina De Comelli, and the secretaries of the Department of Theoretical Physics, University of Trieste, Sabrina Gaspardis and Rosita Glavina for their precious help and assistance.
The application of quantum mechanics to information related fields such as communication, computation and cryptography is a fast growing line of research that has been witnessing an outburst of theoretical and experimental results, with possible practical applications. On the one hand, quantum cryptography with its impact on secrecy of transmission is having its first important actual implementations; on the other hand, the recent advances in quantum optics, ion trapping, BEC manipulation, spin and quantum dot technologies allow us to put to direct test a great deal of theoretical ideas and results. These achievements have stimulated a reborn interest in various aspects of quantum mechanics, creating a unique interplay between physics, both theoretical and experimental, mathematics, information theory and computer science. In view of all these developments, it appeared timely to organize a meeting where graduate students and young researchers could be exposed to the fundamentals of the theory, while senior experts could exchange their latest results. The activity was structured as a school followed by a workshop, and took place at The Abdus Salam International Center for Theoretical Physics (ICTP) and The International School for Advanced Studies (SISSA) in Trieste, Italy, from 12–23 June 2006. The meeting was part of the activity of the Joint European Master Curriculum Development Programme in Quantum Information, Communication, Cryptography and Computation, involving the Universities of Cergy–Pontoise (France), Chania (Greece), Leuven (Belgium), Rennes1 (France) and Trieste (Italy). This special issue of Journal of Physics A: Mathematical and Theoretical collects 22 contributions from well known experts who took part in the workshop. They summarize the present day status of the research in the manifold aspects of quantum information. The issue is opened by two review articles, the first by G Adesso and F Illuminati discussing entanglement in continuous variable systems, the second by T Prosen, discussing chaos and complexity in quantum systems. Both topics have theoretical as well as experimental relevance and are likely to witness a fast growing development in the near future. The remaining contributions present more specific and very recent results. They involve the study of the structure of quantum states and their estimation (B Baumgartner et al , C King et al , S Olivares et al , D Petz et al and W van Dam et al ), of entanglement generation and its quantification (G Brida et al , F Ciccarello et al , G Costantini et al , O Romero-Isart et al , D Rossini et al , A Serafini et al and D Vitali et al ), of randomness related effects on entanglement behaviour (I Akhalwaya et al , O Dahlsten et al and L Viola et al ), and of abstract and applied aspects of quantum computation and communication (K Audenart, G M D'Ariano et al , N Datta et al , L C Kwek et al and M Nathanson et al ). We would like to express our gratitude to the European Commission, the Abdus Salam ICTP, SISSA and Eurotech SpA (Amaro, Udine, Italy) for financial and/or logistic support. Special thanks also go to the workshop secretary Marina De Comelli, and the secretaries of the Department of Theoretical Physics, University of Trieste, Sabrina Gaspardis and Rosita Glavina for their precious help and assistance.
The application of quantum mechanics to information related fields such as communication, computation and cryptography is a fast growing line of research that has been witnessing an outburst of theoretical and experimental results, with possible practical applications. On the one hand, quantum cryptography with its impact on secrecy of transmission is having its first important actual implementations; on the other hand, the recent advances in quantum optics, ion trapping, BEC manipulation, spin and quantum dot technologies allow us to put to direct test a great deal of theoretical ideas and results. These achievements have stimulated a reborn interest in various aspects of quantum mechanics, creating a unique interplay between physics, both theoretical and experimental, mathematics, information theory and computer science. In viewof all these developments, it appeared timely to organize a meeting where graduate students and young researchers could be exposed to the fundamentals of the theory, while senior experts could exchange their latest results. The activity was structured as a school followed by a workshop, and took place at The Abdus Salam International Center for Theoretical Physics (ICTP) and The International School for Advanced Studies (SISSA) in Trieste, Italy, from 12–23 June 2006. The meeting was part of the activity of the Joint European Master Curriculum Development Programme in Quantum Information, Communication, Cryptography and Computation, involving the Universities of Cergy–Pontoise (France), Chania (Greece), Leuven (Belgium), Rennes1 (France) and Trieste (Italy). This special issue of Journal of Physics A: Mathematical and Theoretical collects 22 contributions from well known experts who took part in the workshop. They summarize the present day status of the research in the manifold aspects of quantum information. The issue is opened by two reviewarticles, the first byGAdesso and F Illuminati discussing entanglement in continuous variable systems, the second by T Prosen, discussing chaos and complexity in quantum systems. Both topics have theoretical as well as experimental relevance and are likely to witness a fast growing development in the near future. The remaining contributions present more specific and very recent results. They involve the study of the structure of quantum states and their estimation (B Baumgartner et al, C King et al, S Olivares et al, D Petz et al and W van Dam et al), of entanglement generation and its quantification (G Brida et al, F Ciccarello et al, G Costantini et al, O Romero-Isart et al, D Rossini et al, A Serafini et al and D Vitali et al), of randomness related effects on entanglement behaviour (I Akhalwaya et al, O Dahlsten et al and L Viola et al), and of abstract and applied aspects of quantum computation and communication (K Audenart, G M D'Ariano et al, N Datta et al, L C Kwek et al and M Nathanson et al). We would like to express our gratitude to the European Commission, the Abdus Salam ICTP, SISSA and Eurotech SpA (Amaro, Udine, Italy) for financial and/or logistic support. Special thanks also go to the workshop secretary Marina De Comelli, and the secretaries of the Department of Theoretical Physics, University of Trieste, Sabrina Gaspardis and Rosita Glavina for their precious help and assistance.
Quantum information science is an area of study based on the idea
that information science depends on quantum effects in physics. It includes
theoretical issues in computational models as well as more experimental topics
in quantum physics including what can and cannot be done with quantum
information. Subfields include: Quantum computing, Quantum error correction,
Quantum complexity theory, Quantum cryptography and its generalization, quantum
communication, Quantum communication complexity, Quantum entanglement, Quantum
dense coding, Quantum teleportation.
In the
present book, fifteen typical literatures about Quantum Communication published
on international authoritative journals were selected to introduce the
worldwide newest progress, which contains reviews or original researches on
Communication, mechanics, optics, ect. We hope this book can demonstrate
advances in Quantum Communication as well as give references to the
researchers, students and other related people.
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.
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 meeting was attended by over 50 participants from more than 10 countries and three continents. It brought together mathematicians, physicists and computer scientists working on quantum information and computation. Experts were present as well as young participants, both at predoctoral level as well as postdoctoral level. The focus was on the problems of entanglement and decoherence, aiming at the formulation and discussion of precise concepts, developments of models and their interrelations, and the discussion of experiments in relation with the theory. Special attention was given to recent developments, and to furthering interaction and co-operations between the different groups. The scientific programm focused mainly on the following subjects: 1) Quantum Entanglement and Nonlocality: including Bell-type inequalities (theoretical and experimental studies), equivalence of quantum states under local unitary transformations. 2) Quantum Separability: separability criteria for multiple quantum mixed states in arbitrary dimension. 3) Decoherence: study of models; quantum error corrections, fault tolerant computation, multiparticle problems. 4) Sources of Quantum Entanglement. 5) Quantum Information: quantum cloning, teleportation, key distribution, algorithms. 6) Quantum Measurement and Quantum Optics; Holonomic quantum gates; Quantum semigroups; Continuum Observation. 7) Mathematical Quantum and non commutative structures in connection with quantum information theory. 20 lectures were presented, including 15 surveys and 5 concentrating on specific recent results. There were 10 informal evening lectures on 3 topics: entanglement, control and decoherence. Besides 7 informal talks were presented in 2 round table discussions. All presentations and discussions amply demonstrated the vitality and actuality of this area of research and the fascinating interrelations between the different specialities it involves. The organizers and participants would like to take this opportunity to thank the Mathematisches Forschungsinstitut Oberwolfach for having provided a comfortable and inspiring environment for the meeting and the scientific work.