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Results in Physics

Giant gain from spontaneously generated coherence in Y-type double quantum dot structure

Baqer Obaid Al-Nashy, Sonia Razzaghi, Muwaffaq Abdullah Al-Musawi, H. Rasooli Saghai, Amin Habbeb AL-Khursan

Published Jan 1, 2017• 15 citations
Publisher

Abstract

A theoretical model was presented for linear susceptibility using density matrix theory for Y-configuration of double quantum dots (QDs) system including spontaneously generated coherence (SGC). Two SGC components are included for this system: V, and Λ subsystems. It is shown that at high V-component, the system have a giga gain. At low Λ-system component; it is possible to controls the light speed between superluminal and subluminal using one parameter by increasing SGC component of the V-system. This have applications in quantum information storage and spatially-varying temporal clock.

DOI
10.1016/j.rinp.2017.06.018

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A theoretical model was presented for linear susceptibility using density matrix theory for Y-configuration of double quantum dots (QDs) system including spontaneously generated coherence (SGC). Two SGC components are included for this system: V, and Λ subsystems. It is shown that at high V-component, the system have a giga gain. At low Λ-system component; it is possible to controls the light speed between superluminal and subluminal using one parameter by increasing SGC component of the V-system. This have applications in quantum information storage and spatially-varying temporal clock.
A model was presented for linear susceptibility in ladder-plus-Y configuration of double quantum dot system using density matrix theory and including spontaneously generated coherence of Λ-type system. Wetting layer and quantum dot inhomogeneity were considered in the calculations, which gives a practical description of double quantum dot structures well. With increasing spontaneously generated coherence from Λ-component, the dispersion was increased and shifted under spontaneously generated coherence. The inclusion of wetting layer under spontaneously generated coherence increases gain which coincides with the published results. A possibility of slow light was predicted.
We introduce a Y-configuration model for a double quantum dot (QD) system, which is modeled for Kerr nonlinearity using the density matrix theory. Inhomogeneity in QDs is included in the calculations of the real part (Kerr) and the imaginary part (absorption) of the density matrix, which has not been covered before in Kerr calculations. Five configurations are studied: Y, ladder, Λ, staircase, and weak probe. Frequency detunings, controlling fields, and phases are used to study the structures. Our system shows high controllability as well as a giant Kerr dispersion, propagation without distortion, wide electromagnetic induced transparency, and switching between subluminal to superluminal propagation by tuning its fields.
We have introduced a Y-configuration model from the double-quantum-dot (QD) system to study third-order Kerr nonlinearity based on the density-matrix method. Inhomogeneity in QDs has been included in the calculations of the real (Kerr) and imaginary (absorption) parts of the density matrix, which has not been covered in the earlier Kerr calculations. Our system exhibits high controllability with a single parameter. Giant Kerr dispersion, propagation without distortion, wide electromagnetic-induced transparency, and switching between subluminal to superluminal propagation are obtained by tuning its fields. Controlling and cycling fields can also control the system in addition to the pump field.
A model of the dynamical equations of the density matrix describes double tunnelling between double quantum dot (QD) system states, this is to study Kerr nonlinearity in QD structure. Inhomogeneity in the QD system is included which is not included in earlier studies of Kerr nonlinearity in QDs. Possibilities of subluminal and superluminal light propagation and switching between them are examined. Double tunnelling is shown to obtain giant Kerr dispersion compared with single tunnelling. High conduction- and low valence-band tunnelling components are required to obtain high Kerr dispersion. Working with one tunnel component reduced Kerr dispersion and switching between subluminal and superluminal can be obtained and the EIT window can be removed.
In an open / type system with the spontaneously generated coherence (SGC), when the probe and driving fields have different frequencies, the switching of the group velocity of the probe pulse from subluminal to superluminal is realized not only by adjusting values of the relative phase between the probe and driving fields but also by varying values of the incoherent pumping rate. For the subluminal propagation, the system always exhibits the probe absorption, however, the superluminal propagation is always companied with gain of the probe field.