Nonequilibrium dynamics of spin-boson models from phase space methods

An accurate description of the nonequilibrium dynamics of systems with coupled spin and bosonic degrees of freedom remains theoretically challenging, especially for large system sizes and in higher than one dimension. Phase space methods such as the Truncated Wigner Approximation (TWA) have the advantage of being easily scalable and applicable to arbitrary dimensions. In this work we adapt the TWA to generic spin-boson models by making use of recently developed algorithms for discrete phase spaces [Schachenmayer, PRX 5, 011022 (2015)]. Furthermore we go beyond the standard TWA approximation by applying a scheme based on the Bogoliubov-Born-Green-Kirkwood-Yvon (BBGKY) hierarchy of equations [Pucci, PRB 93, 174302 (2016)] to our coupled spin-boson model. This allows in principle to study how systematically adding higher order corrections improves the convergence of the method. To test various levels of approximation we study an exactly solvable spin-boson model which is particularly relevant for trapped-ion arrays. Using TWA and its BBGKY extension we accurately reproduce the time evolution of a number of one- and two-point correlation functions in several dimensions and for arbitrary number of bosonic modes.Comment: 10+5 pages, 5 figure

Intersection SPaT Estimation by means of Single-Source Connected Vehicle Data

The file attached to this record is the author's final peer reviewed version.Current traffic management systems in urban networks require real-time estimation of the traffic states. With the development of in-vehicle and communication technologies, connected vehicle data has emerged as a new data source for traffic measurement and estimation. In this work, a machine learning-based methodology for signal phase and timing information (SPaT) which is highly valuable for many applications such as green light optimal advisory systems and real-time vehicle navigation is proposed. The proposed methodology utilizes data from connected vehicles travelling within urban signalized links to estimate the queue tail location, vehicle accumulation, and subsequently, link outflow. Based on the produced high-resolution outflow estimates and data from crossing connected vehicles, SPaT information is estimated via correlation analysis and a machine learning approach. The main contribution is that the single-source proposed approach relies merely on connected vehicle data and requires neither prior information such as intersection cycle time nor data from other sources such as conventional traffic measuring tools. A sample four-leg intersection where each link comprises different number of lanes and experiences different traffic condition is considered as a testbed. The validation of the developed approach has been undertaken by comparing the produced estimates with realistic micro-simulation results as ground truth, and the achieved simulation results are promising even at low penetration rates of connected vehicles

A chip-scale integrated cavity-electro-optomechanics platform

We present an integrated optomechanical and electromechanical nanocavity, in which a common mechanical degree of freedom is coupled to an ultrahigh-Q photonic crystal defect cavity and an electrical circuit. The sys- tem allows for wide-range, fast electrical tuning of the optical nanocavity resonances, and for electrical control of optical radiation pressure back-action effects such as mechanical amplification (phonon lasing), cooling, and stiffening. These sort of integrated devices offer a new means to efficiently interconvert weak microwave and optical signals, and are expected to pave the way for a new class of micro-sensors utilizing optomechanical back-action for thermal noise reduction and low-noise optical read-out.Comment: 11 pages, 7 figure

The effect of direct and indirect education on attitudes of parents of children with attention-deficit/hyperactivity disorder towards medication treatments

Background and aims: Attention-deficit/hyperactivity disorder (ADHD) is one of the most common childhood behavioral disorders causing hyperactivity, attention deficit and education decline among children. Regarding the importance of medication treatment, this study was performed to compare the effect of two methods (Direct and Indirect) of education of parents of children with ADHD on their attitudes about medication, treatment satisfaction and medication compliance. Methods: In this clinical trial study, eighty parents of children with ADHD, referred to child psychiatry clinic in Shahrekord were randomly assigned to direct and indirect education groups. The first group (direct education) was attended in groups four sessions. The second group was given education booklet with the same content. Participants were evaluated before and one month after education in terms of their attitudes to medication, treatment satisfaction and treatment compliance. Results: 61 parents of 81 participants continued the study. After intervention, the mean scores of attitudes about medication and satisfaction with treatment were significantly improved in the direct education group (P0.05). Both groups had significantly increased treatment compliance one month after education (P<0.001). Change of mean score attitudes to medication consumption at the end of the periods was significantly different in direct group compared to indirect education group (P<0.01). Conclusion: Direct education was more effective than indirect education on improvement of attitudes towards medication and increase in treatment satisfaction, and both methods resulted in increased medication compliance. Regarding the importance of medication treatment in this disorder, using results of this study can have significant influence on function of children with this disorder in family and school environment

Linear and nonlinear capacitive coupling of electro-opto-mechanical photonic crystal cavities

We fabricate and characterize a microscale silicon electro-opto-mechanical system whose mechanical motion is coupled capacitively to an electrical circuit and optically via radiation pressure to a photonic crystal cavity. To achieve large electromechanical interaction strength, we implement an inverse shadow mask fabrication scheme which obtains capacitor gaps as small as 30 nm while maintaining a silicon surface quality necessary for minimizing optical loss. Using the sensitive optical read-out of the photonic crystal cavity, we characterize the linear and nonlinear capacitive coupling to the fundamental 63 MHz in-plane flexural motion of the structure, showing that the large electromechanical coupling in such devices may be suitable for realizing efficient microwave-to-optical signal conversion.Comment: 8 papers, 4 figure