"Along with these developments, personal microwave technology has enabled strong non-linear effects at the photon level, leading to readily observable novel parameter regimes in quantum optics. Circuit QED has opened up new opportunities to explore the rich physics of quantum information processing (QIP) and quantum optics (QO), making them scalable on the road to quantum computing. However, we must also discuss some of the challenges involved. Quantum Technologies (QT) is a cross-disciplinary field that has made great progress in recent years. Technologies that can explicitly represent individual quantum states, as well as superposition and entanglement, are now being developed to exploit the 'strange' properties of quantum mechanics. In quantum communication, individual or entangled photons are used to securely send data, while quantum simulation utilizes well-controlled quantum systems that are less accessible. Interest is growing in higher dimensional quantum states and quantum communication, as the extended availability of Hilbert space and greater information capacity, along with increased noise elasticity, offer many advantages and new research possibilities. Let's focus our attention on the benefits of higher dimensional quantum states for quantum communication, as shown by Kuditz and others. Nevertheless, it has been demonstrated that higher dimensional quantum states can also provide improvements in many other areas."
"Along with these developments, personal microwave technology has enabled strong non-linear effects at the photon level, leading to readily observable novel parameter regimes in quantum optics. Circuit QED has opened up new opportunities to explore the rich physics of quantum information processing (QIP) and quantum optics (QO), making them scalable on the road to quantum computing. However, we must also discuss some of the challenges involved. Quantum Technologies (QT) is a cross-disciplinary field that has made great progress in recent years. Technologies that can explicitly represent individual quantum states, as well as superposition and entanglement, are now being developed to exploit the 'strange' properties of quantum mechanics. In quantum communication, individual or entangled photons are used to securely send data, while quantum simulation utilizes well-controlled quantum systems that are less accessible. Interest is growing in higher dimensional quantum states and quantum communication, as the extended availability of Hilbert space and greater information capacity, along with increased noise elasticity, offer many advantages and new research possibilities. Let's focus our attention on the benefits of higher dimensional quantum states for quantum communication, as shown by Kuditz and others. Nevertheless, it has been demonstrated that higher dimensional quantum states can also provide improvements in many other areas."
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
This book provides a comprehensive and organized study of quantum technology, focusing on principles, mathematical foundations, and practical realizations of quantum teleportation and other processes in the field of quantum information. It starts with the basic principles of quantum mechanics (wave-particle duality, for instance) superposition and measurement theory all helping as the theoretical backbone of current quantum science. In addition to these basics, we provide a concise introduction and discussion of quantum energy or the quantization of energy levels, energy eigenstates and Planck’s constant, which determines what happens in microscopic systems allowing quantum theory an overlap with data from physical observables. Building on these principles, the book introduces quantum states and quantum entanglement, highlighting their non-classical correlations and their crucial role in facilitating quantum communication protocols. This book also discusses quantum gates and quantum circuits as the units of quantum computation and how quantum information is computed and manipulated by using controlled unitary operations. Also, it discusses the impact of both quantum decoherence and environmental noise which pose significant difficulties to coherent quantum systems and dependable information transmission. It discusses methods of error correction and coherence . This book further expanded to quantum cryptography and secure communications with more importance on protocols like quantum key distribution which make use of quantum principles to provide provable security. Quantum computing architectures and algorithms are also measured and various physical implementations and computational models that strive to produce scalable quantum processors are outlined. Problems and limitations of quantum teleportation are critically examined and these are, reliability issues, channel losses, scaling, and resource limitations. Lastly, the book ends by outlining the future of quantum technology, investigating the new technologies and opportunities, the possible advances, and the revolutionary use of quantum technologies in the fields of computation, communication and secure information processing.
In this talk I shall present a brief overview on some recent exciting experimental progress towards scalable quantum information processing (QIP), e.g., quantum communication, quantum computation and quantum simulation, via manipulation of photonic qubits. Building on our long experience in research on multi-photon entanglement, we are working on a number of experiments in the field of QIP with particular emphasis on linear optical quantum computation and free space quantum communication. It is foreseen that with ongoing development, quantum communication over 1000 km scale and coherent quantum manipulation of up to a few tens photonic qubits shall be feasible in the next five years.
Quantum information processing (QIP) is an interdisciplinary field concerned with the development of computers and information processing systems that utilize quantum mechanical properties of nature to carry out their function. QIP systems have become vastly more practical since the turn of the century. Today, QIP applications span imaging, cryptographic security, computation, and simulation (quantum systems that mimic other quantum systems). \nMany important strategies improve quantum versions of classical information system hardware, such as single photon detectors and quantum repeaters. Another more abstract strategy engineers high-dimensional quantum state spaces, so that each successful event carries more information than traditional two-level systems allow. Photonic states in particular bring the added advantages of weak environmental coupling and data transmission near the speed of light, allowing for simpler control and lower system design complexity. \n \nIn this dissertation, numerous novel, scalable designs for practical high-dimensional linear-optical QIP systems are presented. First, a correlated photon imaging scheme using orbital angular momentum (OAM) states to detect rotational symmetries in objects using measurements, as well as building images out of those interactions is reported. Then, a statistical detection method using chains of OAM superpositions distributed according to the Fibonacci sequence is established and expanded upon. It is shown that the approach gives rise to schemes for sorting, detecting, and generating the recursively defined high-dimensional states on which some quantum cryptographic protocols depend. \n \nFinally, an ongoing study based on a generalization of the standard optical multiport for applications in quantum computation and simulation is reported upon. The architecture allows photons to reverse momentum inside the device. This in turn enables realistic implementation of controllable linear-optical scattering vertices for carrying out quantum walks on arbitrary graph structures, a powerful tool for any quantum computer. It is shown that the novel architecture provides new, efficient capabilities for the optical quantum simulation of Hamiltonians and topologically protected states. Further, these simulations use exponentially fewer resources than feedforward techniques, scale linearly to higher-dimensional systems, and use only linear optics, thus offering a concrete experimentally achievable implementation of graphical models of discrete-time quantum systems.
Photons are very promising resources for the whole field of quantum information processing. Bulk optics are currently not suitable for the realization of complex quantum optical schemes due to several drawbacks. The ongoing miniaturization of photonic structures due to the availability of sophisticated nanofabrication has provided huge opportunities for physical research of novel phenomena in nanophotonic systems and quantum technological applications. These include quantum information processing such as quantum computing, quantum communication, quantum metrology, and quantum sensing. Quantum communication is already quite advanced with several quantum key distribution (QKD) systems commercially available offering absolute security. Photonic quantum technologies are enabling breakthroughs in experimental tests of quantum physics and are close to practical applications of quantum technologies in imaging, secure communications, ultrasensitive metrology and quantum computing. There are several advantages to encoding a quantum bit onto a photon: the preparation and manipulation of single photons is easy, and the photonic qubit is a natural candidate for quantum imaging and communications. Furthermore, the qubit can be encoded in various degrees of freedom such as on the position, phase, time-bin, energy, angular momentum, polarization of the photon—or a combination of these. This flexibility leads to enormous opportunities for scientific exploration and in practical applications. This special issue on “Photonic Quantum Technologies” presents selected papers on photonic quantum systems from leading groups in the world. The articles represent a flavor of the cutting-edge research that is going on in this area. The studied material systems range from molecules to semiconductor quantum emitters. A major challenge is the design of telecom photon emitters with high efficiency, good yield, spectral purity, stability and the possibility of mass manufacture. We believe that this Special Issue will provide an overview of recent exciting developments in the field of photonic quantum technologies, serving to keep researchers up-to-date with the latest progress and spurring on new concepts in this field.
Within the last two decades, quantum technologies (QT) have made tremendous progress, moving from Nobel Prize award-winning experiments on quantum physics (1997: Chu, Cohen-Tanoudji, Phillips; 2001: Cornell, Ketterle, Wieman; 2005: Hall, Hänsch-, Glauber; 2012: Haroche, Wineland) into a cross-disciplinary field of applied research. Technologies are being developed now that explicitly address individual quantum states and make use of the 'strange' quantum properties, such as superposition and entanglement. The field comprises four domains: quantum communication, where individual or entangled photons are used to transmit data in a provably secure way; quantum simulation, where well-controlled quantum systems are used to reproduce the behaviour of other, less accessible quantum systems; quantum computation, which employs quantum effects to dramatically speed up certain calculations, such as number factoring; and quantum sensing and metrology, where the high sensitivity of coherent quantum systems to external perturbations is exploited to enhance the performance of measurements of physical quantities. In Europe, the QT community has profited from several EC funded coordination projects, which, among other things, have coordinated the creation of a 150-page QT Roadmap ( http://qurope.eu/h2020/qtflagship/roadmap2016 ). This article presents an updated summary of this roadmap.