Quantum Trajectories and Measurements in Continuous Time - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Quantum Trajectories and Measurements in Continuous Time write by Alberto Barchielli. This book was released on 2009-07-11. Quantum Trajectories and Measurements in Continuous Time available in PDF, EPUB and Kindle. Quantum trajectory theory is largely employed in theoretical quantum optics and quantum open system theory and is closely related to the conceptual formalism of quantum mechanics (quantum measurement theory). However, even research articles show that not all the features of the theory are well known or completely exploited. We wrote this monograph mainly for researchers in theoretical quantum optics and related ?elds with the aim of giving a self-contained and solid p- sentation of a part of quantum trajectory theory (the diffusive case) together with some signi?cant applications (mainly with purposes of illustration of the theory, but which in part have been recently developed). Another aim of the monograph is to introduce to this subject post-graduate or PhD students. To help them, in the most mathematical and conceptual chapters, summaries are given to ?x ideas. Moreover, as stochastic calculus is usually not in the background of the studies in physics, we added Appendix A to introduce these concepts. The book is written also for ma- ematicians with interests in quantum theories. Quantum trajectory theory is a piece of modern theoretical physics which needs an interplay of various mathematical subjects, such as functional analysis and probability theory (stochastic calculus), and offers to mathematicians a beautiful ?eld for applications, giving suggestions for new mathematical developments.
Quantum Trajectories and Measurements in Continuous Time
Quantum Trajectories and Measurements in Continuous Time - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Quantum Trajectories and Measurements in Continuous Time write by Alberto Barchielli. This book was released on 2009-07-21. Quantum Trajectories and Measurements in Continuous Time available in PDF, EPUB and Kindle. This course-based monograph introduces the reader to the theory of continuous measurements in quantum mechanics and provides some benchmark applications. The approach chosen, quantum trajectory theory, is based on the stochastic Schrödinger and master equations, which determine the evolution of the a-posteriori state of a continuously observed quantum system and give the distribution of the measurement output. The present introduction is restricted to finite-dimensional quantum systems and diffusive outputs. Two appendices introduce the tools of probability theory and quantum measurement theory which are needed for the theoretical developments in the first part of the book. First, the basic equations of quantum trajectory theory are introduced, with all their mathematical properties, starting from the existence and uniqueness of their solutions. This makes the text also suitable for other applications of the same stochastic differential equations in different fields such as simulations of master equations or dynamical reduction theories. In the next step the equivalence between the stochastic approach and the theory of continuous measurements is demonstrated. To conclude the theoretical exposition, the properties of the output of the continuous measurement are analyzed in detail. This is a stochastic process with its own distribution, and the reader will learn how to compute physical quantities such as its moments and its spectrum. In particular this last concept is introduced with clear and explicit reference to the measurement process. The two-level atom is used as the basic prototype to illustrate the theory in a concrete application. Quantum phenomena appearing in the spectrum of the fluorescence light, such as Mollow’s triplet structure, squeezing of the fluorescence light, and the linewidth narrowing, are presented. Last but not least, the theory of quantum continuous measurements is the natural starting point to develop a feedback control theory in continuous time for quantum systems. The two-level atom is again used to introduce and study an example of feedback based on the observed output.
Quantum Trajectories and Their Extremal-probability Paths
Quantum Trajectories and Their Extremal-probability Paths - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Quantum Trajectories and Their Extremal-probability Paths write by Philippe Lewalle. This book was released on 2021. Quantum Trajectories and Their Extremal-probability Paths available in PDF, EPUB and Kindle. "Quantum theory posits that measurements are invasive: It describes an interactive process, mediating all knowledge of quantum properties, in which an observer probes a quantum system and draws inferences about its behavior based on the outcomes they receive. This dissertation emphasizes the theory, and several applications, of time-continuous monitoring of quantum systems. The particular results described below follow two threads: One concerns the behavior of extremal-probability trajectories, derived from a path integral description and action-extremization principle applied to diffusive quantum trajectories. The other concerns the use of continuous measurement for generating and preserving entanglement between two remote qubits. Two new phenomena arising in the optimal paths, derived as the first-order variational solutions of a stochastic action, are presented herein. Multiple solutions which extremize the probability of the measurement record may connect the same initial and final quantum state over the same time interval; these groups of multipath solutions arise as dynamical instabilities in the optimal path dynamics, and in close mathematical analogy with the formation of caustics in optics. Furthermore, the proliferation of these quantum caustics is closely connected to chaotic behavior among extremal-probability paths. This optimal path chaos that we characterize fundamentally relies on measurement, and can occur in a system with no immediate classical analog, such as a qubit; this is in contrast with typical explorations of quantum chaos. The other thread developed herein concerns methods to generate and protect entanglement between two remote qubits by joint continuous measurement of their spontaneous emission. We characterize the entanglement dynamics arising in quantum jump trajectories due to continuous photon counting, as well as in diffusive trajectories arising from homodyne monitoring. These processes generate equivalent entanglement yield on average, despite qualitatively different dynamics in their respective individual realizations. Finally, some strategies for feedback control based on these measurements are developed, with the goal of increasing the entanglement yield and lifetime. Specifically, we illustrate how implement a measurement un-doing and control procedure, that traps the two-qubit dynamics in limit cycles around Bell states for each type of measurements mentioned"--Pages xiii-xiv.
Continuous Quantum Measurements and Path Integrals
Continuous Quantum Measurements and Path Integrals - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Continuous Quantum Measurements and Path Integrals write by M.B Mensky. This book was released on 2017-10-19. Continuous Quantum Measurements and Path Integrals available in PDF, EPUB and Kindle. Advances in technology are taking the accuracy of macroscopic as well as microscopic measurements close to the quantum limit, for example, in the attempts to detect gravitational waves. Interest in continuous quantum measurements has therefore grown considerably in recent years. Continuous Quantum Measurements and Path Integrals examines these measurements using Feynman path integrals. The path integral theory is developed to provide formulae for concrete physical effects. The main conclusion drawn from the theory is that an uncertainty principle exists for processes, in addition to the familiar one for states. This implies that a continuous measurement has an optimal accuracy-a balance between inefficient error and large quantum fluctuations (quantum noise). A well-known expert in the field, the author concentrates on the physical and conceptual side of the subject rather than the mathematical.
Quantum Measurement Theory and its Applications
Quantum Measurement Theory and its Applications - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Quantum Measurement Theory and its Applications write by Kurt Jacobs. This book was released on 2014-08-14. Quantum Measurement Theory and its Applications available in PDF, EPUB and Kindle. Recent experimental advances in the control of quantum superconducting circuits, nano-mechanical resonators and photonic crystals has meant that quantum measurement theory is now an indispensable part of the modelling and design of experimental technologies. This book, aimed at graduate students and researchers in physics, gives a thorough introduction to the basic theory of quantum measurement and many of its important modern applications. Measurement and control is explicitly treated in superconducting circuits and optical and opto-mechanical systems, and methods for deriving the Hamiltonians of superconducting circuits are introduced in detail. Further applications covered include feedback control, metrology, open systems and thermal environments, Maxwell's demon, and the quantum-to-classical transition.
