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.
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.
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.
Extending beyond the achievements already made in the so-called "first quantum revolution", quantum technologies hold the potential to revolutionize the design and management of protocols for new emerging technologies in observation, communication, simulation, metrology and sensing. The second quantum revolution strives to exploit fundamental quantum properties, such as entangled quantum states, the wave nature of particles, coherent superpositions and non-classical correlations in leading edge theoretical and experimental research advancements.
The 20th century has witnessed the rise of quantum mechanics and its fueled scientific and technological revolution. The humankind is now on the verge of a second quantum revolution sparked by quantum information science and engineering (QISE). Entanglement as a quintessential quantum resource lies at the heart of QISE, giving rise to a plethora of quantum-enabled or enhanced capabilities that shift the landscape of communication, sensing, and computing. This talk will focus on sensing and precision metrology enhanced by entanglement, a unique and radically new resource for information processing. I will describe our recent experimental advances in entanglement-based quantum machine learning for data classification and entangled sensor networks for precise radiofrequency and optomechanical sensing. A pathway toward large-scale quantum sensor networks and prospects for future applications underpinned by quantum-enhanced sensing will also be discussed.
The current frontier of our understanding of the physical universe is dominated by quantum phenomena. Uncovering the prospects and limitations of acquiring and processing information using quantum effects is an outstanding challenge in physical science. This thesis presents an analysis of several new model systems and applications for quantum information processing and metrology.\n\nFirst, we analyze quantum optomechanical systems exhibiting quantum phenomena in both optical and mechanical degrees of freedom. We investigate the strength of non-classical correlations in a model system of two optical and one mechanical mode. We propose and analyze experimental protocols that exploit these correlations for quantum computation.\n\nWe then turn our attention to atom-cavity systems involving strong coupling of atoms with optical photons, and investigate the possibility of using them to store information robustly and as relay nodes. We present a scheme for a robust two-qubit quantum gate with inherent error-detection capabilities. We consider several remote entanglement protocols employing this robust gate, and we use these systems to study the performance of the gate in practical applications.\n\nFinally, we present a new protocol for running multiple, remote atomic clocks in quantum unison. We show that by creating a cascade of independent Greenberger-Horne-Zeilinger states distributed across the network, the scheme asymptotically reaches the Heisenberg limit, the fundamental limit of measurement accuracy. We propose an experimental realization of such a network consisting of neutral atom clocks, and analyze the practical performance of such a system.
Quantum technologies harness the properties of controlled quantum mechanical systems for applications in computation, communication and metrology, and enable us to further our understanding of fundamental physics. Quantum hardware is designed to manipulate complex and fragile many-particle quantum states, which requires exquisite control machinery, advanced software and near-complete isolation from the surrounding environment. With sufficient capabilities, quantum computers with large registers of quantum bits will perform classically intractable calculations such as quantum chemistry simulations. Quantum key distribution will provide completely secure communications across the world and quantum metrology will enable measurement precision beyond today's capabilities. While quantum technologies are far from surpassing classical hardware today, the vision and potential impact has sparked a world-wide research effort, both theoretical and experimental, to develop a quantum computer. The most sophisticated current quantum technologies have control over small numbers of quantum bits and are limited by environmental decoherence processes. While progress in developing quantum hardware is ongoing, designing and demonstrating new algorithms and protocols for quantum information is a thriving research field. Photonics provides an ideal platform for small-scale proof-of-concept quantum experiments, which are the focus of this thesis. In the coming decades, we will see the realisation of quantum hardware capable of applications that outperform any classical computer. In this thesis, I present several protocols and algorithms for quantum information science and technology, which are implemented in quantum photonic experiments. The applications of these works include robust quantum tomography, quantum state relocation, quantum enhanced data recovery and probing fundamental causality in quantum mechanics. The works presented here are based on two photon experiments from a prototypical spontaneous parametric down-conversion source, which provides an excellent test-bed for quantum information experiments. Photons can be used to encode quantum information in a range of different degrees of freedom. This versatility, along with compatibility with existing technology gives photonics a great advantage in the development of quantum hardware.