The Electron Transport Characteristics Of The Mesoscopic Double Quantum Dot System

The research on quantum information and quantum computing has attracted more and more attentions in the last decade.With the appearance of solid state quantum computing and the continuous development of micro devices in experiments,quantum mechanical effect will play a leading role in Mesoscopic system.This will affect the development of quantum measurement,quantum computing,and quantum manipulation,especially in the processing and storage of information.Quantum measurement is the key to quantum mechanical interpretation and quantum information application.It is beneficial to study the process of decoherence and relaxation induced by the environment,so as to realize the quantum computing and quantum manipulation.In fact,the quantum coherence is so hard to maintain.This is mainly due to the inevitable coupling between the quantum system and the external environment(including the detector)that can lead to the decoherence.How to better measure the decoherence dynamics and achieve the quantum control with decoherence suppression has become one of the important research content in the field of quantum information and quantum computation.The paper aims to explore the properties of electronic transport of a double quantum dot system.We theoretically study the quantum measurement of a double quantum dot coupled to environments by Bloch equations with an additional vector based on the full counting statistics.Using a quantum point contact as a detector,we accurately calculate the current,the Fano factor,and the waiting time,respectively,to characterize the dynamical properties in two kinds of environments.In the dissipative case,the asymmetrical Fano factor is enhanced with the increase in deocoherence rates and suppressed as the growth of relaxation rates,and the super-Poissonian noise is mainly due to the effects of a dynamical channel blockade and quantum coherence.In the pure dephasing case,the symmetrical Fano factor is magnified,which can be attributed to the quantum Zeno effect.Moreover,we show that the distribution of the average waiting time exhibits good agreement with the variation tendency of the current.Our paper provides an effective method in handling quantum measurement.There are five chapters in this paper.It is mainly related to the study of the dynamical properties of the double quantum dot coupled to the detector in the environments,focusing on the intrinsic physical mechanism and the characteristics of electron transport.In the first chapter,we give the background of our research,then make a brief introduction of the remarkable characteristics and significance of the double quantum dot,such as the tunneling effect,the Coulomb blockade effect,and quantum dots in medical,biological,and luminescent materials.In the second chapter,we mainly introduce the theory of quantum transport and quantum measurement of the double quantum dot,and further describe the proposed and applied many-body Schrodinger equation theory of S.A.Gurvitz.We also explore the basic physical mechanism of electron transfer and the dynamical equation coupled to the detector.At the end of the second chapter,the theory of full counting statistics and shot noise are introduced.In the third chapter,we deduce the existing master equations for quantum measurement and propose an additional Bloch vector to characterize the dynamic properties.The dynamical equation of the double quantum dot coupled to the detector in the dissipative environment are calculated.In addition,we also analyze the effects of relaxation and decoherence rates for the dynamic properties,and also confirm that the relaxation process lead to the asymmetrical structure of the Fano factor.The characteristics of average current and Fano factor under different energy bias are further discussed.Furthermore,we explore the dynamical properties of quantum measurement of mesoscopic semiconductor devices which are different from those macroscopic devices,such as the quantum Zeno effect and the Coulomb blockade effect.In the fourth chapter,we continue to study the dynamic properties of the double quantum dot with an additional Bloch vector in the pure dephasing environment.We calculate and analyze the effects of the dephasing and decoherence rates for average current,Fano factor,and average waiting time distribution.The influence and physical mechanism of the detector on system dynamics are further explored.In the fifth chapter,we summarize the work of the previous chapters and an outlook.Experimentally,we can also select and adjust other parameters to obtain different levels of quantum interference and the dwelling time of electrons,such as the coupling strength between the double quantum dot system,the external laser field,the applied magnetic field,etc.We predict that the environmental relaxation rate and decoherence rate can also be quantified by measuring the Fano factor.The theoretical study of electron transport characteristics of the double quantum dot promotes the understanding of quantum effects and physical mechanisms,and provides theoretical guidance for quantum computing,quantum manipulation,and the application of quantum entanglement in practice.In addition,it can provide a very good theoretical foundation for the use of molecular systems to achieve quantum computing in the future.