High frequency polarization switching of a thin ferroelectric film

We consider both experimentally and analytically the transient oscillatory process that arises when a rapid change in voltage is applied to a $Ba_xSr_{1-x}TiO_3$ ferroelectric thin film deposited on an $Mg0$ substrate. High frequency ($\approx 10^{8} rad/s$) polarization oscillations are observed in the ferroelectric sample. These can be understood using a simple field-polarization model. In particular we obtain analytic expressions for the oscillation frequency and the decay time of the polarization fluctuation in terms of the material parameters. These estimations agree well with the experimental results

Fully quantum mechanical dynamic analysis of single-photon transport in a single-mode waveguide coupled to a traveling-wave resonator

We analyze the dynamics of single photon transport in a single-mode waveguide coupled to a micro-optical resonator using a fully quantum mechanical model. We examine the propagation of a single-photon Gaussian packet through the system under various coupling conditions. We review the theory of single photon transport phenomena as applied to the system and we develop a discussion on the numerical technique we used to solve for dynamical behavior of the quantized field. To demonstrate our method and to establish robust single photon results, we study the process of adiabatically lowering or raising the energy of a single photon trapped in an optical resonator under active tuning of the resonator. We show that our fully quantum mechanical approach reproduces the semi-classical result in the appropriate limit and that the adiabatic invariant has the same form in each case. Finally, we explore the trapping of a single photon in a system of dynamically tuned, coupled optical cavities.Comment: 24 pages, 10 figure

Stability analysis with Pole-zero Identification: unveiling the critical dynamics of microwave circuits

The term pole-zero identification refers to obtaining the poles and zeros of a linear (or linearized) system described by its frequency response. This is usually done using optimization techniques (such as least squares, maximum likelihood estimation, or vector fitting) that fit a given frequency response of the linear system to a transfer function defined as the ratio of two polynomials [1], [2]. This kind of linear system identification in the frequency domain has numerous applications in a wide variety of engineering fields, such as mechanical systems, power systems, and electromagnetic compatibility. In the microwave domain, rational approximation is increasingly used to obtain black-box models of complex passive structures for model order reduction and efficient transient simulation. An extensive bibliography on the matter can be found in [3]-[6]. In this article, we focus on a different application of pole-zero identification. We review the different ways in which pole-zero identification can be applied to nonlinear circuit design, for power-amplifier stability analysis, and more. We provide a comprehensive view of recent approaches through illustrative application examples. Other uses for rational-approximation techniques are beyond the scope of this article.This work was supported in part by the French Space Agency (CNES) under projects R-S10/TG-0001-019 and R-S14/TG-0001-019; by a joint Ph.D. research grant from CNES and Thales Alenia Space, France; by project TEC2015-67217-R (MINECO/FEDER); and by the Basque Country Government through project IT1104-16

Spectroscopy of Three-Particle Entanglement in a Macroscopic Superconducting Circuit

We study the quantum mechanical behavior of a macroscopic, three-body, superconducting circuit. Microwave spectroscopy on our system, a resonator coupling two large Josephson junctions, produced complex energy spectra well explained by quantum theory over a large frequency range. By tuning each junction separately into resonance with the resonator, we first observe strong coupling between each junction and the resonator. Bringing both junctions together into resonance with the resonator, we find spectroscopic evidence for entanglement between all three degrees of freedom and suggest a new method for controllable coupling of distant qubits, a key step toward quantum computation.Comment: 4 pages, 3 figure