Quantum Bit Encoding Based On Semiconductor Quantum Dots

Owing to the pioneers' continuos effort and great works,quantum information has become one of the most concerned research frontiers.Beyond that,quantum computa-tion has been paid widespread attentions by science research institutes and governments around the world.In the meantime,the technological state of the art of the semiconduc-tor industry is reaching the limit with the rapid development of half a century.Structures into nanoscale can be achieved utilizing the well-developed micro and nano fabricaiton technique,which makes it possible to manipulating a single atom or electron precisely.On this basis,scientists exploited several kinds of physical systems for realizing quan-tum computation.Semiconductor quantum dot shows the highest potential as one of the candidates for quantum computation.The spin or charge states of electrons trapped in quantum dots can be used for constructing a qubit,and performing the universal sets of gates needed for quantum computation through the assistance of magnetic or electric field.The quantum states of electrons that chosen to be the computational base states become the central issue of quantum dot based qubit research.In this thesis,a brief summary of several qubit encoding methods is introduced and the latest results of our own researches are presented.The thesis is outlined as follows:1.A brief introduction into quantum computaion and quantum bit.The structure of an identical quantum dot and the properties of single and double dot.The fabrication process of a quantum dot.2.The encoding and manipulating of two kinds of spin qubit.High spin states re-search in a double quantum dot containing three electrons.3.The encoding and manipulating of a double quantum dot charge qubit.The Lar-mor,Ramsey and echo experiments on charge qubit.4.The hybrid qubit based on Silicon and GaAs double quantum dot.5.The characterisation of a linear triple quantum dot and the strange PAT phe-nomenon in triple dot.6.The proposal of forming a pair of parallel energy levels in an asymmetrically cou-pled triple quantum dot.The experimental realization and coherent manipulation of the parallel states in triple quantum dot.