Study Of Quantum Dots Fabrication On Low-dimensional Materials And Quantum Transport Property

As a quasi-zero-dimensional structure,quantum dot is a box that contains electrons or holes.Coding the electros or the holes inside the box,quantum dot can be used as a basic unit for quantum computation,quantum bit.On the one or two dimensional material,one can easily acquire quantum dots from etching or placing gate structures with voltages applied.Nowadays low-dimensional materials play very important roles in quantum computation field.Research on fabrication and quantum transport properties of low-dimensional material quantum dot is vital part of quantum computation research.Here we are going to study two-dimensional material graphene and one-dimensional material germanium hut wires.The main content of this thesis is listed below:1、Briefly introduced background of quantum computation,constant interaction model,and basic transport images of single and double quantum dots(DQDs).Compared coherence differences of several materials,and introduced some properties of Si/Ge materials used in this thesis;2、Introduced quantum dot fabrication on Ge hut wires;3、Designed a new type of superconducting reflection line resonator,and coupled to graphene double quantum dots.Studied how the graphene DQDs affect the microwave signal in the resonator,and gave a method to extract key parameters of the system from microwave response.Use resonator as a probe,we got the stability diagram of the DQDs,and extracted dephasing time of graphene charge qubit as well as its 4-fold dependence of charge number.Moreover,we achieved non-classical long-range correlation between DQDs mediated by the resonator;4、Microwave influence on graphene DQDs were studied.Introduced a method to determine energy detuning of the DQD,then measured charge noise power spectrum density.Proved microwave heating effect on graphene by observe white noise floor shift.Microwave influence on coherence property is also studied.When exceed a certain power,microwave heating becomes a major source of decoherence,which explains the difficulty in microwave manipulation experiment on graphene;5、Exploring more suitable quantum bit material.We designed and fabricated single quantum dot on Ge hut wire,and analyzed transport properties of it.We studied the energy splitting of each energy level in the dot and their expression on the coulomb diamond.Combined with the experimental data,a best window were chosen for Zeeman splitting observation.Through the observation we distinguished different quantum states and associated hole number parities,acquired g-factor as well.The main innovations of this thesis are:1、Designed and fabricated a new type of 2D resonator;2、Use the resonator as probe,we extracted dephasing rate of graphene as well as its 4-fold dependence of charge number;3、Use the resonator as media,we achieved non-classical long-range correlation between DQDs;4、We performed measurement of charge noise power spectrum density,confirmed microwave heating effect on graphene;5、Discovered that microwave heating becomes a major source of decoherence even under a relatively small microwave power,pointing out the limit on graphene qubits;6、Designed and fabricated single hole type quantum dots on Ge hut wires;7、Studied the transport property of hole type quantum dots on Ge hut wires,observed Zeeman splitting,distinguished different quantum states and associated hole number parities,acquired g-factor.