The International System of Units (SI) is the world's most widely used system of measurement, used every day in commerce and science, and is the modern form of the metric system. It currently comprises the meter (m), the kilogram (kg), the second (s), the ampere (A), the kelvin (K), the candela (cd) and the mole (mol)). The system is changing though, units and unit definitions are modified through international agreements as the technology of measurement progresses, and as the precision of measurements improves. The SI is now being redefined based on constants of nature and their realization by quantum standards. Therefore, the underlying physics and technologies will receive increasing interest, and not only in the metrology community but in all fields of science. This book introduces and explains the applications of modern physics concepts to metrology, the science and the applications of measurements. A special focus is made on the use of quantum standards for the realization of the forthcoming new SI (the international system of units). The basic physical phenomena are introduced on a level which provides comprehensive information for the experienced reader but also provides a guide for a more intense study of these phenomena for students.
The International System of Units (SI) is the world's most widely used system of measurement, used every day in commerce and science, and is the modern form of the metric system. It currently comprises the meter (m), the kilogram (kg), the second (s), the ampere (A), the kelvin (K), the candela (cd) and the mole (mol)). The system is changing though, units and unit definitions are modified through international agreements as the technology of measurement progresses, and as the precision of measurements improves. The SI is now being redefined based on constants of nature and their realization by quantum standards. Therefore, the underlying physics and technologies will receive increasing interest, and not only in the metrology community but in all fields of science. This book introduces and explains the applications of modern physics concepts to metrology, the science and the applications of measurements. A special focus is made on the use of quantum standards for the realization of the forthcoming new SI (the international system of units). The basic physical phenomena are introduced on a level which provides comprehensive information for the experienced reader but also provides a guide for a more intense study of these phenomena for students.
Advances in quantum mechanics have long underpinned metrology by enabling practical realizations of units through quantum effects. With the 2019 SI revision, traceability is anchored in defined fundamental constants, reinforcing the quantum-mechanical basis of modern standards. In parallel, quantum technologies are transitioning from laboratory science to engineering and early industrial deployment, bringing familiar pressures for integration, reliability, cost reduction, supply-chain formation, and standardization. The direction of benefit is thus reversing: metrology and precision measurement are becoming enabling infrastructure for the industrialization of quantum technologies. Against this backdrop, this paper surveys the metrology and precision-measurement capabilities required across representative quantum-computing modalities and identifies where electrical and related metrology can contribute to the development, characterization, and reliable operation of quantum hardware. We then discuss cross-cutting measurement needs and standardization opportunities that recur across platforms, and note how similar frameworks can extend to emerging quantum-sensing applications.
In November 2018, during the 26th General Conference on Weights and Measures (CGPM) in Versailles, France, a landmark resolution was adopted to redefine four base units of the International System of Units (SI)(https://www.bipm.org/en/committees/cg/cgpm/26-2018/resolution-1). The kilogram, mole, ampere, and kelvin were redefined in terms of fundamental physical constants: the Planck constant(h), the Avogadro constant(NA), the elementary charge(e), and the Boltzmann constant(k), respectively. As illustrated in Figure 1(a), the new SI framework defines all seven base units based on fundamental constants, marking a complete transition of metrology into the quantum era. This system has been in effect globally since May 20, 2019, on World Metrology Day.
This book is an up-to-date introduction to the quantum theory of measurement, a fast developing field of intense current interest to scientists and engineers for its potential high technology applications. It is also a subject of importance to students for its central role in the foundations of quantum mechanics. Although the main principles of the field were elaborated in the 1930s by Bohr, Schrödinger, Heisenberg, von Neumann and Mandelstam, it was not until the 1980s that technology became sufficiently advanced to allow its application in real experiments. Quantum measurement is now central to many ultra-high technology developments, such as squeezed light, single atom traps, and searches for gravitational radiation. It is also considered to have great promise for computer science and engineering, particularly for its applications in information processing and transfer. The book contains a pedagogical introduction to the relevant theory written at a level accessible to those with only a modest background in quantum mechanics. It then goes on to discuss aspects of the design of practical quantum measurement systems. This book is essential reading for all scientists and engineers interested in the potential applications of technology near the quantum limit. It will also serve as an ideal supplement to standard quantum mechanics textbooks at the advanced undergraduate or graduate level.
The control of individual quantum systems promises a new technology for the 21st century - quantum technology. This book is the first comprehensive treatment of modern quantum measurement and measurement-based quantum control, which are vital elements for realizing quantum technology. Readers are introduced to key experiments and technologies through dozens of recent experiments in cavity QED, quantum optics, mesoscopic electronics, and trapped particles several of which are analysed in detail. Nearly 300 exercises help build understanding, and prepare readers for research in these exciting areas. This important book will interest graduate students and researchers in quantum information, quantum metrology, quantum control and related fields. Novel topics covered include adaptive measurement; realistic detector models; mesoscopic current detection; Markovian, state-based and optimal feedback; and applications to quantum information processing.
Quantum mechanics has profoundly reshaped our knowledge of the physical world: a deep comprehension of the quantum nature of matter yielded to the so-called first quantum revolution, enabling transformative technologies ranging from lasers to semiconductor de- vices, being at the heart of the digital revolution characterizing the second half of the XXth century. Furthermore, the capability of manipulating and controlling individual quantum systems enabled a totally different working paradigm, obeying the logic im- posed by quantum physics, paving the way, at the end of the XXth and the beginning of the XXIst century, for the second quantum revolution. Modern quantum technologies, including quantum computation, quantum simulation, quantum metrology and quantum communication rely on peculiar quantum phenomena, such as superposition, entangle- ment and coherence to perform tasks beyond classical capabilities. This thesis proposes quantum metrology as a unifying conceptual and methodological framework to investigate problems lying at the intersection of fundamental quantum physics and quantum information science. More in detail, it addresses theoretical and experimental protocols to certify the presence of quantum correlations (namely, quantum steering), as well as to design secure sensing in quantum networks under realistic assump- tions. Moreover, it also suggest how tunable-strength measurement-based strategies can be used to extract information from complex systems even in seemingly inaccessible sce- narios. Overall, this thesis proposes quantum metrology as a framework through which the purest nature of information can be probed, certified and secured at the most fundamental level.