Today's resistance thermometers can routinely measure temperatures with uncertainties of >1 mK–100 mK over multiple decades of temperatures. As the modern economy continues to evolve, so does the measurement infrastructure. In recent years, there has been a considerable progress in the development of novel temperature sensing technologies driven by advances in quantum information science and nano-photonics. Quantum technologies in particular hold the promise of field-deployable primary thermometry whilst ultra-stable nanophotonic thermometers could displace resistance thermometers as commodity sensors.
Today's resistance thermometers can routinely measure temperatures with uncertainties of >1 mK–100 mK over multiple decades of temperatures. As the modern economy continues to evolve, so does the measurement infrastructure. In recent years, there has been a considerable progress in the development of novel temperature sensing technologies driven by advances in quantum information science and nano-photonics. Quantum technologies in particular hold the promise of field-deployable primary thermometry whilst ultra-stable nanophotonic thermometers could displace resistance thermometers as commodity sensors.
Quantum sensing is the most exciting quantum technology and it has the most potential to change our lives in the next decade and beyond. Quantum sensors will offer new capabilities with benefits for medicine, defense, intelligence, extractive industries and many others. Quantum sensing is a precursor technology to quantum computing and communications. Quantum sensors use quantum properties and effects to measure or sense physical things. This chapter explores quantum sensing as a topic in its own right, because the capabilities of quantum sensing are surprising and offer new forms of knowledge discovery and at new levels of analysis. Furthermore quantum sensors are here today---indeed, they have been in use for more than fifty years.
Recent years have witnessed a growing interest in understating the limitations imposed by quantum noise in precision measurements and devising techniques to reduce it. The attention is currently turning to the simultaneously estimation of several parameters of interest, driven by its promising potential across a wide range of sensing applications as well as fueled by experimental progress in various optical and atomic platforms. Here, we provide a comprehensive overview of key research directions in multiparameter quantum sensing and metrology, highlighting both opportunities and challenges. We introduce the basic framework, discuss ultimate sensitivity bounds, optimal measurement strategies, and the role of quantum incompatibility, showing important differences with respect to single-parameter estimation. Additionally, we discuss emerging experimental implementations in distributed quantum sensing, including cutting-edge optimization techniques. This review aims to bridge the gap between theory and experiments, paving the way for the next-generation of quantum sensors and their integration with other quantum technologies.
The rapidly developing quantum technologies and thermodynamics have put forward a requirement to precisely control and measure the temperature of microscopic matter at the quantum level. Many quantum thermometry schemes have been proposed. However, precisely measuring low temperature is still challenging because the obtained sensing errors generally tend to diverge with decreasing temperature. Using a continuous-variable system as a thermometer, we propose non-Markovian quantum thermometry to measure the temperature of a quantum reservoir. A mechanism to make the sensing error $\ensuremath{\delta}T$ scale with the temperature T as the Landau bound $\ensuremath{\delta}T\ensuremath{\simeq}T$ in the full-temperature regime is discovered. Our analysis reveals that it is the quantum criticality of the total thermometer-reservoir system that causes this enhanced sensitivity. Efficiently avoiding the error-divergence problem, our result gives an efficient way to precisely measure the low temperature of quantum systems.
This report explores the profound and symbiotic relationship between quantum technology and classical electronics, highlighting their convergence as a transformative force in modern engineering and computation. It details how classical electronic systems are indispensable for the control, measurement, and operation of nascent quantum technologies—including quantum computing, communication, sensing, and simulation—particularly through advanced cryogenic and interface architectures. Concurrently, the inherent scaling limitations of classical electronics at the nano scale are driving innovation inspired by quantum mechanical principles, leading to the development of next-generation devices and the exploration of exotic quantum materials. The analysis addresses significant technical challenges such as noise, scalability, latency, and thermal management, alongside the immense economic and strategic opportunities presented by this frontier. Ultimately, the report projects a future defined by seamless quantum-classical hybrid systems, underscoring that the advancement of quantum technology is deeply reliant on breakthroughs in classical electronics, physics, and computer science. Quantum technology represents a transformative frontier that bridges fundamental physics, advanced electronics, and cutting-edge computer science. Rooted in the principles of quantum mechanics—such as superposition, entanglement, and tunneling—quantum technologies are reshaping how information is processed, transmitted, and measured. The interplay between physics provides the theoretical foundation, while electronics enables precise control and manipulation of quantum systems through devices like qubits and quantum sensors. Meanwhile, computer science contributes with algorithms, error correction, and software frameworks essential for quantum computation and communication. This interdisciplinary synergy is driving breakthroughs in quantum computing, quantum cryptography, and quantum sensing, promising profound impacts on industries ranging from cybersecurity to materials science and artificial intelligence.
Quantum sensing leverages quantum resources to enable ultra-precise measurements beyond classical limits, driving transformative advancements in metrology. Optical fiber quantum sensing, integrating optical fiber sensing with quantum technologies, enhances measurement precision and sensitivity from multiple perspectives, such as exploring high-sensitivity optical fiber sensing installations and generating high-quality optical fiber quantum states. Following decades of comprehensive investigations and remarkable advances in optical fiber quantum sensing technology, this review systematically examines research achievements in this field through two complementary perspectives: one is the basic principle of generating optical fiber quantum states and their applications in sensing and the other is optical fiber quantum interferometers and their applications in sensing. Finally, examine current opportunities and challenges as well as the future development of optical fiber quantum sensing.
Quantum technologies make it possible to obtain reproducible standards at any time and place without traceability chain. Centro Español de Metrología (CEM) has been using them for more than 20 years for standards such as voltage and resistance. Nowadays, the second quantum revolution has burst into the field of metrology in a radical way, offering tools and methods with unprecedented capabilities and transforming the classical view of this science, giving the opportunity to overcome limits that were considered unsurpassed. NMIs have a duty and obligation to take this potential and transform it into tangible benefits for science, industry and society. This goal, which is a major challenge for the whole community, is even greater for small and medium-sized NMIs. However, far from being a barrier, this should be an invitation to actively participate in this revolution. CEM has assumed a firm commitment to develop these quantum technologies. This has led to design and implement a comprehensive strategy to completely transform the Institute, from the most classical conception of metrology towards future quantum developments. As part of this strategy, several projects are being carried out with the aim of being an active actor in this global transformation, such as the following: An optical clock based on Calcium 40 ions is being implemented. This device will make use of an ion trap, a state-of-the-art technology which will enhance the capabilities of CEM offering higher levels of accuracy in our realisations. Furthermore, this project aims to establish, with ROA, national and international collaborations that will allow us to contribute to the advancement of this technology in the global scientific community. On another hand, optomechanical sensors have been proposed by the International Thermometry community which, by combining light-mater interaction with the vibrations of the device at the nanometric scale, allows the construction of primary quantum thermometer. CEM has been working in nano-photonic sensors based on photonic crystals in Si. It has been developed a free space-measuring set-up working at 1550 nm from 10 °C to 80 °C for the calibration of photonic integrated circuits (PICs). In addition, CEM is developing an experiment for the materialization of the pressure unit, the Pascal, by refractometry technique. This experiment has the aim of covering the pressure range of 1 Pa to 30 kPa with a target expanded uncertainty (k = 2) of 2 mPa + 10 ppm. This experiment is part of the European integrated metrological infrastructure for a SI-traceable quantum-pascal, and it is expected to be one pillar for primary materializations of other quantities. These developments are part of the ongoing transformation at CEM, with the aim of becoming a key player in the implementation of quantum technologies in metrology. Beyond our progress, the goal is to serve as a showcase and inspiration for all NMIs, regardless of their size or resources, to understand the importance of being part of this revolution. Our aim is to demonstrate that, with a clear strategy and a strong commitment, it is possible to be part of this historic change.