Electron cascade for distant spin readout

The spin of a single electron in a semiconductor quantum dot provides a well-controlled and long-lived qubit implementation. The electron charge in turn allows control of the position of individual electrons in a quantum dot array, and enables charge sensors to probe the charge configuration. Here we show that the Coulomb repulsion allows an initial charge transition to induce subsequent charge transitions, inducing a cascade of electron hops, like toppling dominoes. A cascade can transmit information along a quantum dot array over a distance that extends by far the effect of the direct Coulomb repulsion. We demonstrate that a cascade of electrons can be combined with Pauli spin blockade to read out distant spins and show results with potential for high fidelity using a remote charge sensor in a quadruple quantum dot device. We implement and analyse several operating modes for cascades and analyse their scaling behaviour. We also discuss the application of cascade-based spin readout to densely-packed two-dimensional quantum dot arrays with charge sensors placed at the periphery. The high connectivity of such arrays greatly improves the capabilities of quantum dot systems for quantum computation and simulation.

Modeling of the radiation induced electromagnetic field in finely-disperse media

Algorithms for supercomputer modeling of the radiation electromagnetic field in heterogeneous materials of a complex finely-dispersed structure are constructed. A geometric model of a heterogeneous medium is created using Stilinger-Lubachevsky algorithms for multimodal structures. The model includes a system of detectors for statistical evaluation of functionals on the space of solutions of the photon-electron cascade transport equations. Algorithms for the three-dimensional approximation of the results of modeling the radiation transport in a fine-dispersed medium to an electrodynamic difference grid are developed. The approximation methods based on the technology of neural networks. The method of numerical solution of the complete system of Maxwell's equations for calculating the electromagnetic field in a fine-dispersed medium is worked out. The results of demonstration calculations of the electromagnetic field are presented. The results of the calculations show that the spatial distribution of the radiation electromagnetic field has a sharply inhomogeneous structure caused by the presence of boundaries of materials with different radiation properties.

Benzothiadiazole Based Cascade Material to Boost the Performance of Inverted Ternary Organic Solar Cells

A conjugated, ladder-type multi-fused ring 4,7-dithienbenzothiadiazole:thiophene derivative, named as compound ‘T’, was for the first time incorporated, within the PTB7:PC71BM photoactive layer for inverted ternary organic solar cells (TOSCs) realization. The effective energy level offset caused by compound T between the polymeric donor and fullerene acceptor materials, as well as its resulting potential as electron cascade material contribute to an enhanced exciton dissociation, electron transfer facilitator and thus improved overall photovoltaic performance. The engineering optimization of the inverted TOSC, ITO/PFN/PTB7:Compound T(5% v/v):PC71BM/MoO3/Al, resulted in an overall power conversion efficiency (PCE) of 8.34%, with a short-circuit current density (Jsc) of 16.75 mA cm−2, open-circuit voltage (Voc) of 0.74 V and a fill factor (FF) of 68.1%, under AM1.5G illumination. This photovoltaic performance was improved by approximately 12% with respect to the control binary device.