Nonlinear quantum input-output analysis using Volterra series

Quantum input-output theory plays a very important role for analyzing the dynamics of quantum systems, especially large-scale quantum networks. As an extension of the input-output formalism of Gardiner and Collet, we develop a new approach based on the quantum version of the Volterra series which can be used to analyze nonlinear quantum input-output dynamics. By this approach, we can ignore the internal dynamics of the quantum input-output system and represent the system dynamics by a series of kernel functions. This approach has the great advantage of modelling weak-nonlinear quantum networks. In our approach, the number of parameters, represented by the kernel functions, used to describe the input-output response of a weak-nonlinear quantum network, increases linearly with the scale of the quantum network, not exponentially as usual. Additionally, our approach can be used to formulate the quantum network with both nonlinear and nonconservative components, e.g., quantum amplifiers, which cannot be modelled by the existing methods, such as the Hudson-Parthasarathy model and the quantum transfer function model. We apply our general method to several examples, including Kerr cavities, optomechanical transducers, and a particular coherent feedback system with a nonlinear component and a quantum amplifier in the feedback loop. This approach provides a powerful way to the modelling and control of nonlinear quantum networks.Comment: 12 pages, 7 figure

The Poisson multiple access channel

Cover title. "Presented in part at IEEE Info Theory Workshop, June 9-13, Haifa, Israel."Includes bibliographical references (p. 29-32).Research supported by the Laboratory for Information and Decision Systems, Massachusetts Institute of Technology. DAAH04-95-1-0103Lapidoth, A., Shamai, Shlomo (Shitz)

Development and Application of Pure Rotational CARS for Reactive Flows

The thesis deals with the further development of pure rotational coherent anti-Stokes Raman spectroscopy (RCARS) for improving the capabilities of gas phase thermometry. The main effort has been to make the technique more robust when employed under a wide range of temperatures and operational conditions. A primary aim has been to investigate the impact of collisional broadening on N2 RCARS thermometry, especially in an environment in which N2 is perturbed by H2. Since an interaction of this sort is species-specific and temperature-dependent, it plays a very critical role in RCARS thermometry. It was found that in a sequence of implementation, validation and application, thermometric accuracy could be improved by the implementation of N2-H2 line-broadening coefficients. Investigation of these topics involved exploring a novel technique of time-resolved picosecond RCARS for direct measurements of S-branch N2-N2/N2-H2 Raman linewidths. The N2 and O2 Herman-Wallis factors, used to quantify vibration-rotation interaction and breakdown of the rigid rotor model were also investigated. This correction affects the line-intensities, and also has an impact on RCARS thermometry. Conclusions regarding the sensitivity related to this factor could be achieved by employing different expressions available in the specialized literature. A theoretical code for N2O concerned with thermometric accuracy in a set of temperature-calibrated cell experiments was developed and was validated. This work expands the list of RCARS molecules previously developed, and points to interesting possibilities such as that of improving the thermometric precision. The technique was also applied to flame diagnostics. Temperatures were mapped along the centerline of a one-dimensional flame provided on a McKenna burner, this serving as important input data for other related optical techniques. The homogeneity of this flame was investigated for two different operational shielding co-flows, those of N2 and of air. Measurements were also performed in a low-swirl turbulent premixed flame, for validating existing models of large eddy simulations. Probability density functions for a large range of temperatures (300 K to 1700 K) and relative O2 concentrations were provided. The simultaneous measurements of these quantities provided a better understanding than possessed earlier of air entrainment from the surroundings

Theory and applications of free-electron vortex states

Both classical and quantum waves can form vortices: with helical phase fronts and azimuthal current densities. These features determine the intrinsic orbital angular momentum carried by localized vortex states. In the past 25 years, optical vortex beams have become an inherent part of modern optics, with many remarkable achievements and applications. In the past decade, it has been realized and demonstrated that such vortex beams or wavepackets can also appear in free electron waves, in particular, in electron microscopy. Interest in free-electron vortex states quickly spread over different areas of physics: from basic aspects of quantum mechanics, via applications for fine probing of matter (including individual atoms), to high-energy particle collision and radiation processes. Here we provide a comprehensive review of theoretical and experimental studies in this emerging field of research. We describe the main properties of electron vortex states, experimental achievements and possible applications within transmission electron microscopy, as well as the possible role of vortex electrons in relativistic and high-energy processes. We aim to provide a balanced description including a pedagogical introduction, solid theoretical basis, and a wide range of practical details. Special attention is paid to translate theoretical insights into suggestions for future experiments, in electron microscopy and beyond, in any situation where free electrons occur.Comment: 87 pages, 34 figure