We study the efficient preparation of the exciton state in a hybrid nanostructure composed by a semiconductor quantum dot and a metallic nanoparticle, when starting from the ground state, using pulses derived with the method of shortcuts to adiabaticity. We show with numerical simulations that high levels of exciton population can be obtained for a wide range of interparticle distances and for short pulse durations. This behavior appears also to be robust against small positioning errors of the system. The fidelity of the population inversion degrades for smaller distances and longer pulses, as the nonlinear terms in the equations, expressing the quantum dot–metal nanoparticle interaction, become stronger and affect the evolution for longer times. The present work is expected to help schemes toward the generation of single photons on demand or ultrafast nanoswitches, where the controlled population inversion in semiconductor quantum dots coupled to metal nanoparticles is an important task.
We show that for the two widely used configurations of the double-
Λ
atom–light coupling scheme, one where the control fields are applied in the same
Λ
-subsystem and another where they are applied in different
Λ
-subsystems, the forward propagation of the probe and signal fields is described by the same set of equations. We then use optimal control theory to find the spatially dependent optimal control fields that maximize the conversion efficiency from the probe to the signal field, for a given optical density. This work can find application in the implementation of efficient frequency and orbital angular momentum conversion devices for quantum information processing, as well as to be useful for many other applications using the double-
Λ
atom–light coupling scheme.
We consider a hybrid nanostructure composed by semiconductor quantum dot coupled to a metallic nanoparticle and investigate the efficient creation of biexciton state in the quantum dot, when starting from the ground state and using linearly polarized laser pulses with on-off modulation. With numerical simulations of the coupled system density matrix equations, we show that a simple on-off-on pulse-sequence, previously derived for the case of an isolated quantum dot, can efficiently prepare the biexciton state even in the presence of the nanoparticle, for various interparticle distances and biexciton energy shifts. The pulse durations in the sequence are obtained from the solution of a transcendental equation.
How to efficiently prepare the biexciton state in a semiconductor quantum dot placed in the vicinity of a metal nanoparticle is investigated, with control pulses calculated using shortcuts to adiabaticity and specificaly transitionless quantum driving. The quantum dot is considered to be initialized in its ground state. It is numerically demonstrated that the proposed scheme can generate biexciton population values close to unity, for a broad span of interparticle distances and small to moderate values of the biexciton binding energy, when using short laser pulses. It is also shown that these results are robust for small errors in the nanoparticle placement. When the interparticle distance is decreased or the duration of the applied pulses is increased, the population transfer to the biexciton state is reduced. The reason is that for shorter distances the nonlinear terms in the density matrix equation, arising due to exciton-plasmon interaction, become stronger, while for longer pulses the influence of these unwanted terms is prolonged. Similarly, the fidelity is also reduced for larger values of the biexciton binding energy and longer pulses. This work may be exploited in research fields like quantum information processing and high speed nanoswitches, where a key procedure is the efficient biexciton state preparation in quantum dots.
We study the potential for controlled transfer of population to the biexciton state of a semiconductor quantum dot coupled with a metal nanoparticle, under the influence of an electromagnetic pulse with hyperbolic secant shape, and derive analytical solutions of the density matrix equations for both zero and nonzero biexciton energy shifts. These solutions lead to efficient transfer to the biexciton state for various interparticle distances including relatively small values. In certain cases, when the distance between the two particles is small, the transfer of population is strongly modified because of the influence of surface plasmons to the excitons, and the effect is more pronounced for shorter pulses. The hybrid nanostructure that we study has been proposed for generating efficient polarization-entangled photons, and thus, the successful biexciton state preparation considered here is expected to contribute in this line of research.
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