AUTHORS: Dionisis Stefanatos, Nikolaos Iliopoulos, Vasilios Karanikolas, Emmanuel Paspalakis
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ABSTRACT: A basic system with important potential applications in quantum technologies is a quantum dot in the Voigt geometry. The spin states of the quantum dot in the Voigt geometry can act as a prototype qubit which can be manipulated by applied optical fields in order to produce the necessary quantum gates. The basic method for spin initialization in a quantum dot in the Voigt geometry is optical pumping. Here, we propose and analyze a new method for the coherent preparation of the quantum dot spin states based on adiabatic control methods. Specifically, we show that the application of two mutually delayed and partially overlapping optical pulses, similar to those used in stimulated Raman adiabatic passage, can lead to initialization of one of the spin states with high fidelity. We also demonstrate that the fidelity of the method may be increased by integrating the quantum dot with a micropillar cavity. Specifically, we show that a preferential Purcell-enhanced decay rate towards the target spin state, in certain cases, increases the fidelity of spin initialization of the adiabatic method. Our results are based on the numerical solution of the relevant density matrix equations for the quantum dot system, either in an isotropic photonic environment or in a micropillar cavity. The calculations presented in this paper are not limited to quantum dots in micropillar cavities. Similar effects can be obtained by other photonic structures as well, as for example, for quantum dots in photonic crystal cavities.
KEYWORDS: Quantum dot, Optical fields, Voigt geometry, Spin initialization, Adiabatic passage, Purcell effect, Delayed optical pulses
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