The first quantum revolution started in the early 20th century and gave us new rules that govern physical reality. Accordingly, many devices that changed dramatically our lifestyle, such as transistors, medical scanners and lasers, appeared in the market. This was the origin of quantum technology, which allows us to organize and control the components of a complex system governed by the laws of quantum physics. This is in sharp contrast to conventional technology, which can only be understood within the framework of classical mechanics. We are now in the middle of a second quantum revolution. Although quantum mechanics is nowadays a mature discipline, quantum engineering as a technology is now emerging in its own right. We are about to manipulate and sense individual particles, measuring and exploiting their quantum properties. This is bringing major technical advances in many different areas, including computing, sensors, simulations, cryptography and telecommunications. The present collection of selected papers is a clear demonstration of the tremendous vitality of the field. The issue is composed of contributions from world leading researchers in quantum optics and quantum information, and presents viewpoints, both theoretical and experimental, on a variety of modern problems.
The first quantum revolution started in the early 20th century and gave us new rules that govern physical reality. Accordingly, many devices that changed dramatically our lifestyle, such as transistors, medical scanners and lasers, appeared in the market. This was the origin of quantum technology, which allows us to organize and control the components of a complex system governed by the laws of quantum physics. This is in sharp contrast to conventional technology, which can only be understood within the framework of classical mechanics. We are now in the middle of a second quantum revolution. Although quantum mechanics is nowadays a mature discipline, quantum engineering as a technology is now emerging in its own right. We are about to manipulate and sense individual particles, measuring and exploiting their quantum properties. This is bringing major technical advances in many different areas, including computing, sensors, simulations, cryptography and telecommunications. The present collection of selected papers is a clear demonstration of the tremendous vitality of the field. The issue is composed of contributions from world leading researchers in quantum optics and quantum information, and presents viewpoints, both theoretical and experimental, on a variety of modern problems.
Over the past century, quantum theory has taken flight from conceptual breakthroughs, such as wave–particle duality, quantisation of energy, and the uncertainty principle, to practical tools that are the backbone of modern electronics, lasers, semiconductors, and precision measurement systems. In the twenty-first century, this progress under the regime of the second quantum revolution has acquired the ability to directly control, manipulate, and engineer individual quantum systems.Quantum technologies found their pillars in quantum properties, such as superposition, entanglement, and coherence and have exceeded the boundaries of classical physics. The steady theoretical advances, combined with experimental progress, have brought quantum concepts closer to real-life use. Significant progress has made in filed of computation, communication, sensing, navigation, medicine, cyber security, and national defense undr the guidance of quantum technology.This book chapter presents a comprehensive and pedagogical overview of quantum technologies. It highlights quantum computing, quantum communication, and quantum sensing and metrology. The shift of quantum mechanics into practical applications is discussed. Current research trends are reviewed alongside the technological and engineering challenges. The critical issues, such as decoherence, scalability, error correction, standardisation, and workforce development, are discussed, which further highlights the need for global collaboration. Both National governments and the private sector are investing heavily in quantum research. This will act as a booster for quantum technologies to revolutionise information processing, secure communications, and precision measurements. Consequently and will significantly impact the scientific and technological landscape.
Over the past century, quantum theory has taken flight from conceptual breakthroughs, such as wave–particle duality, quantisation of energy, and the uncertainty principle, to practical tools that are the backbone of modern electronics, lasers, semiconductors, and precision measurement systems. In the twenty-first century, this progress under the regime of the second quantum revolution has acquired the ability to directly control, manipulate, and engineer individual quantum systems. Quantum technologies found their pillars in quantum properties, such as superposition, entanglement, and coherence and have exceeded the boundaries of classical physics. The steady theoretical advances, combined with experimental progress, have brought quantum concepts closer to real-life use. Significant progress has made in filed of computation, communication, sensing, navigation, medicine, cyber security, and national defense undr the guidance of quantum technology. This book chapter presents a comprehensive and pedagogical overview of quantum technologies. It highlights quantum computing, quantum communication, and quantum sensing and metrology. The shift of quantum mechanics into practical applications is discussed. Current research trends are reviewed alongside the technological and engineering challenges. The critical issues, such as decoherence, scalability, error correction, standardisation, and workforce development, are discussed, which further highlights the need for global collaboration. Both National governments and the private sector are investing heavily in quantum research. This will act as a booster for quantum technologies to revolutionise information processing, secure communications, and precision measurements. Consequently and will significantly impact the scientific and technological landscape.
This special issue offers a large selection of contributions dealing with recent advances in the theoretical and experimental aspects of quantum correlations and fluctuations. The issue results from a proposal to dedicate a special issue to the topics covered in the 6th International Conference on Squeezed States and Uncertainty Relations (ICSSUR '99) which took place in Naples, Italy on 24-29 May 1999. This proposal was received enthusiastically by the conference organisers, and the unexpectedly large number of contributions indicates the high level of interest in coherent effects in optics and related systems. The published papers encompass a wide range of topics: quantum measurements and noise, quantum interference and correlations, quantum communication and information, generation and characterization of non-classical states of light, squeezed states, and other quantum harmonic oscillators and quantum-like systems. With thanks to the Editor and the Editorial Office for all the work done, the guest editors express the hope that analogous thematic issues could appear in the near future.
This special issue is composed mainly of extended versions of talks and papers presented at the Seventh International Conference on Squeezed States and Uncertainty Relations held in Boston, Massachusetts, USA, on 4-8 June 2001. The conference was hosted by Boston University. The first meeting of this kind took place in College Park, Maryland, USA in 1991 as a small workshop. The second and third meetings were held in Moscow, Russia and Baltimore, USA in 1992 and 1993, respectively. The fourth meeting took place in Taiyuan, Shanxi Province, China in 1995 as an international conference sponsored by the International Union of Pure and Applied Physics. The fifth and sixth meetings were held in Balatonfüred, Hungary and Naples, Italy in 1997 and 1999, respectively. The eighth conference will take place in Puebla, Mexico in 2003. The contributions to this special issue address, in the first instance, the foundations of quantum mechanics and quantum optics, and several modern topics which have been intensively developed during the last decade. Quantum fluctuations, squeezing phenomena and different kinds of nonclassical states of light represent some of the most intensively discussed subjects. In particular, several papers deal with the properties of different kinds of `Schrödinger cat states' modelled in the simplest case by the even and odd coherent states. This paradigm exhibits in the most distinct form such cornerstone properties of quantum mechanics as the superposition principle, which manifests itself in quantum interference and entanglement. The quantum entanglement phenomenon has been studied intensively for the past few years due to its importance, for example, in quantum computer projects. In spite of the fact that this concept was known from the beginning of quantum mechanics, its properties, for example, the most appropriate entanglement measures, are still areas of discussion. Another related aspect of quantum nature is teleportation, which is also a subject of intensive study. The phenomena of dissipations and decoherence of the initial pure states are also very important, because fast decoherence can destroy all the advantages of quantum processes in quantum computing, teleportation and image processing. Due to these aspects, papers concerning various methods of controlling the decoherence, for example, by means of using different kinds of nonlinearities and deformations, are also presented here. From the very beginning of quantum mechanics, the uncertainty relations were basic inequalities distinguishing the classical and quantum worlds. Developing a deeper understanding of the well-known uncertainty relations and striving to find new ones (connected with purity parameters of states, entropy, etc.) is an important aspect of modern research. Recently developed tomographic methods of measuring quantum states (in terms of the Wigner function or other phase-space characteristics) have resulted in the formulation of quantum mechanics in which the standard probability density describes the quantum states in an alternative way to the density matrix or wave function. Some papers devoted to tomographic methods of measuring quantum states and studying different sorts of uncertainty relations are presented here. Group-theoretical methods of studying quantum-mechanical and quantum-optical phenomena, including the group-representation description of light polarization, also attract ongoing interest in the conference series discussions. We hope that this special issue will help readers to obtain an overview of the current trends in modern quantum optics, both experimental and theoretical. Young S Kim University of Maryland, College Park, USA Margarita A Man'ko P.N. Lebedev Physical Institute, Moscow, Russia Alexander Sergienko Boston University, MA, USA Guest Editors
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.
The field of quantum sensing leverages quantum mechanical resources such as superposition, entanglement, and squeezing to surpass classical limits in measurement precision and enable new sensing modalities. This Special Topic Collection in Applied Physics Reviews brings together recent advances spanning theory, materials, device engineering, and applications of quantum sensors. Contributions cover a wide range of platforms, including atomic, solid-state, optomechanics, and photonics, highlighting both fundamental science and emerging technologies. The collection illustrates the transition of quantum sensing from foundational concepts toward scalable technologies and broadens its impact across physics, engineering, and applied sciences.