Switching from positive to negative absorption with electromagnetically induced transparency in circuit quantum electrodynamics

We present a theoretical study of electromagnetically induced transparency （EIT） in a superconducting quantum circuit with a tunable V-shaped energy spectrum derived from two superconducting Josephson charge qubits coupled with each other through a superconducting quantum interference device. Using the density matrix formalism and the steady-state approximation, we obtain the analytical expressions of the first-order matrix element associated with the absorption and dispersion of the probe field for two different V-type schemes. Our results show that, for this superconducting quantum system, it is possible to realize a remarkable phenomenon that dynamic conversion between EIT and EIT with amplification without population inversion. Such a unique optical feature has potential applications in quantum optical devices and quantum information processing.

Non-Intrusive Magneto-Optic Detecting System for Investigations of Air Switching Arcs

In current investigations of electric arc plasmas, experiments based on modern testing technology play an important role. To enrich the testing methods and contribute to the understanding and grasping of the inherent mechanism of air switching arcs, in this paper, a nonintrusive detecting system is described that combines the magneto-optic imaging（MOI） technique with the solution to inverse electromagnetic problems. The detecting system works in a sequence of main steps as follows： MOI of the variation of the arc flux density over a plane, magnetic field information extracted from the magneto-optic（MO） images, arc current density distribution and spatial pattern reconstruction by inverting the resulting field data. Correspondingly, in the system, an MOI set-up is designed based on the Faraday effect and the polarization properties of light, and an intelligent inversion algorithm is proposed that involves simulated annealing（SA）.Experiments were carried out for high current（2 kA RMS） discharge cases in a typical low-voltage switchgear. The results show that the MO detection system possesses the advantages of visualization, high resolution and response, and electrical insulation, which provides a novel diagnostics tool for further studies of the arc.

An Application of the Inverse Solution for Electric Current Distribution From Magnetic Field Measurements in Aluminium Electrolysis Cells

A mathematical theory and the software application based on the full MHD model of the electrolysis cell is used to predict the electric current distribution over the anodes from the measurement of magnetic fields at specifically defined node points assumed to be available from the wireless sensors.The full 3d busbar configuration of two different commercial ceils are used for the model simulations.It is demonstrated that a unique solution for the electric current can be obtained when two sensors per each anode are used to detect the single component of magnetic field.The mathematical software is tested for the sensitivity to the busbar configuration complexity.The ability to monitor continuously the electric current distribution to high accuracy helps to control disturbances and deviations from a normal production process.