Birla Institute of Technology & Science, Pilani - Goa

About: Birla Institute of Technology & Science, Pilani - Goa is a based out in . It is known for research contribution in the topics: Dielectric & Deep learning. The organization has 314 authors who have published 299 publications receiving 2741 citations.

Open quantum systems with local and collective incoherent processes: Efficient numerical simulations using permutational invariance

Abstract: The permutational invariance of identical two-level systems allows for an exponential reduction in the computational resources required to study the Lindblad dynamics of coupled spin-boson ensembles evolving under the effect of both local and collective noise. Here we take advantage of this speedup to study several important physical phenomena in the presence of local incoherent processes, in which each degree of freedom couples to its own reservoir. Assessing the robustness of collective effects against local dissipation is paramount to predict their presence in different physical implementations. We have developed an open-source library in python, the Permutational-Invariant Quantum Solver (PIQS), which we use to study a variety of phenomena in driven-dissipative open quantum systems. We consider both local and collective incoherent processes in the weak-, strong-, and ultrastrong-coupling regimes. Using PIQS, we reproduce a series of known physical results concerning collective quantum effects and extend their study to the local driven-dissipative scenario. Our work addresses the robustness of various collective phenomena, e.g., spin squeezing, superradiance, and quantum phase transitions, against local dissipation processes.

Complex permittivity and microwave absorption properties of BaTiO3–polyaniline composite

Abstract: BaTiO3–polyaniline composites with different mixture ratios, 75/25, 50/50 and 25/75, have been prepared in polyurethane resin, keeping pigment to volume concentration (PVC) constant as ∼25 in all the samples. For this, BaTiO3 powder by oxide route and polyaniline by chemical oxidation route have been synthesized. The complex permittivity ( e ′ r − j e ″ r ) and reflection loss (dB) of the composites have been measured at different microwave frequencies in X-band (8.2–12.4 GHz) employing vector network analyzer model PNA E8364B and software module 85071. Reflection loss (dB) has been calculated for different thicknesses of the composites using measured values of e ′ r and e ″ r . It is found that the absorption properties of the composite improve with increasing % of polyaniline. A maximum reflection loss of −15 dB (97% power absorption) at 10 GHz with a bandwidth of 3 GHz (full frequency width at half of the peak response) has been achieved. Materials can find applications in suppression of electromagnetic interference (EMI), and reduction of radar signature.

Structural, ferroelectric and optical properties of PZT thin films

Abstract: We report on the structural, ferroelectric and optical properties of lead zirconate titanate (PZT) thin films (with a molar ratio of Zr:Ti::65:35) deposited by sol–gel technique on ITO-coated corning 7059 glass substrates. A seed layer of PbTiO3 (0.1mm) was coated by sol–gel on the substrates before depositing PZT. A metal/ferroelectric/metal (MFM) structure was used for electrical property measurements, formed by depositing gold electrodes on top of the film. The films were characterized for C–V, I–V, P–E and optical transmission. Relatively low remnant polarization (Pr ¼ 3:6mC=cm 2 ) was observed for the films. Value of optical band gap was found to be 3.4 eV. The results are discussed.