The Effect Of Phonon Reservoir On The Quantum Properties Of Quantum Dot Systems

Quantum dots are small artificially structured system which governed by the laws of quan-turn mechanics.As the dot' s size,shape,coupling strength and the number of electrons in the dot are all under experimental control,their transport properties are readily measured,so that it has wide application foreground.Semiconductor quantum dots(QDs)embedded in mi-crocavities have established themselves as a new paradigm in cavity quantum electrodynamics(cavity-QED).In recent years,technological progress in the design and fabrication of semi-conductor cavity-QED systems has attracted a lot of attention and enabled them to be used as components in quantum information processing.Solid-state cavity QED(cQED)systems are inherently coupled to the environment,since the emitter is embedded in a solid.The phonon bath serves as a low-frequency reservoir when coupled to the cavity-QED system,the radia-tive properties of the whole system change and lead to some novel physics effects,including phonon-mediated Rabi oscillations,the resonance fluorescence spectrum linewidth of a quan-turn dot can be found in the dependence of its properties on driving field,and the creation of a steady-state population inversion between the bare states of a two-level QD system.In this thesis,we investigate the effect of phonon reservoir on quantum dot cavity quantum electrodynamic systems.According to their different interaction,the photon blockade,quantum interference and squeezing of resonance fluorescence of quantum systems can be realized.Firstly,We theoretically investigate the influence of the phonon bath on photon blockade in a simultaneously driven dot-cavity system.We find an optimal condition for implementing photon blockade by modulating the phase difference and the strengthes of the driving field-s.The second-order correlation function which describes the quantum statistics of the photon field and the mean photon number of the cavity field are discussed.In the absence of phonon effect,as the destructive quantum interference arisen from different transition paths induced by simultaneously driving the dressed QD-cavity system,the strong photon blockade in a moderate quantum dot(QD)-cavity coupling regime occurs.The participation of acoustic-phonon reser-voir produces new transition channels for the QD-cavity system,which leads to the damage of destructive interference.As a result,the photon blockade effect is hindered when taking the electron-phonon interaction into account.It is also found that the temperature of the phonon reservoir is disadvantageous for the generation of photon blockade.Then,We demonstrate how an acoustic phonon bath when coupled to a quantum dot with the help of a bichromatic laser field may effectively form a quantum squeezed reservoir.This ap-proach allows to achieve an arbitrary degree of squeezing of the effective reservoir.It is found that for unequal Rabi frequencies,the effective reservoir may appear as a quantum squeezed field of ordinary or inverted harmonic oscillators.When the Rabi frequencies are equal the effective reservoir appears as a perfectly squeezed field in which the decay of one of the polar-ization quadratures of the quantum dot dipole moment is inhibited,the decay of the quantum dot to a stationary state which depends on the initial coherence is predicted.The effect of the initial coherence on the steady-state dressed-state population distribution and the fluorescence spectrum is discussed in details.The complete polarization of the dressed state population and asymmetric spectra composed of only a single Rabi sideband peak are obtained under strictly resonant excitation.Lastly,We investigate the effects of a phonon reservoir on a system which consists of a two-level quantum dot(QD)driven by a bichromatic laser.By deriving the master equations we find that,in a solid-state phonon reservoir environment,the dynamics of the system is similar to that of a two-level atom interacting with a broadband squeezed vacuum.The population inversion of the system can be realized via adjusting the relative strength of the phonon-induced damping rates of the system.We find that a weak-probe beam can be either absorbed or amplified by the QD system due to the phonon-mediated processes induced by the electron-phonon interaction.Moreover,the quadrature squeezing spectra produced in the resonance fluorescence of the QD system is investigated.