The Theoretical Research Of Quantum Dots Coupled With Microcavity

After the birth of quantum mechanics,quantum information technology has been rising,and today has gotten great progress.Quantum computation is bringing challenges for classical encryption systems due to its amazing abilities in parallel computing.Furthermore,quantum computation has attracted more and more people's attention because of its characteristics of absolute security.Single-photon source has been regarded as a key source in realizing the tasks of quantum key distribution.The single photon sources have also been widely applied in many fields,such as weak absorption measurements and quantum random number generators etc.Quantum dots not only possess discrete energy level structure as atomics,but also own many advantages of semiconductor materials.Besides,it is easier to grow and fabricate and are thus more suitable for generating quantum light source than atomics.For example,it can be used to implement quantum dot lasers,single photon sources which required for quantum key distribution,etc.Whereas,simple research on quantum dots has been unable to meet the needs of scientific research,quantum dots can be combined with the cavity,improving the coupling strength between them,many cavity quantum electrodynamics phenomena can be observed in the experiment.By employing the Master Equation theory,the lasing properties of the quantum dot-microcavity coupling system were studied.For different types of coupling systems,i.e.,“good system” and “more realistic system”,their lasing phenomenon under external pump field were investigated individually.Moreover,the influence of the detuning and the pure dephasing on internal characteristics of the coupling system,such as its second-order correlation function at zero time delay or the number of photons in cavities was analyzed.The numerical simulations show that,for a “good system”,when the detuning between a quantum dot and a cavity is not very large,certain pure dephasing can improve the lasing properties of the coupled system;for a “more realistic system”,due to the difficulty of photon gathering in a cavity under off-resonant conditions,it is very hard to observe the lasing phenomenon.However,pure dephasing will still play an important role on modulating the light field and the photon numbers in the cavity.These results may play positive effects on some research either on lasing with the single quantum dot,or modulating the interaction between light and matter etc.In addition,by using the strong coupling quantum dot cavity system and the numerical simulation of the JC ladder,the method of double pulse excitation is adopted.Thus,we demonstrate complete coherent control of a quantum dot-photonic crystal cavity based quantum-bit.By controlling the excitation power and phase in a two-pulse excitation scheme we achieve access to the full Bloch sphere.Finally,according to the two different coupling model(red,blue detuned),the phonon included in the quantum master equation,the effect of phonons on the fluorescence spectra of the red and blue quantum dot microcavity systems is studied by numerical simulation.The results show that the intensity of phonons is different from that of the red detuned and blue detuned quantum dot microcavity systems.These results provide important theoretical support for the resolution of the resonant quantum dot spectra and the realization of spin manipulation of quantum dots.