Manipulate And Observe Electron States In Double Quantum Dots

In this thesis, observation and manipulation of electron states in semiconductor double quantum dots were investigated experimentally. In the section of observation, we developed a technique of radio-frequency reflectometry measurement. This mea-surement method provides higher bandwidth and sensitivity that ordinary measurement method cannot reach. In manipulation section, we investigated Landau-Zener transition property in charge qubit formed by semiconductor double quantum dots.By the help of controlled Landau-Zener dynamics, we demonstrate a proof of principle quantum simulation of Kibble-Zurek mechanism, which is provides a description of topological structure occurring in the symmetry breaking phase transitions.The main content of this thesis includes:1. Introduced the physical principles, concepts and phenomenon which were related to the following experimentally work of this thesis.2.Briefly introduced the typical nano-fabrication process used to fabricate samples in this thesis. Present detailed step information in every steps. From a hole wafer to samples can be measured in low temperature systems, we draw a step-by-step manual.3.Discuss measurement methods in the point of view of following experimental re-search. From low temperature measuring platform, we introduced the measure-ment methods of sample’s basic property. Moreover, we presented the measure-ment methods used in following experiment.4.Studied the technique of radio-frequency reflectometry measurement. This mea-surement method provides higher bandwidth and sensitivity that ordinary mea-surement method cannot reach. From reflectometry circuit, we discussed the principle of this method, and compared the data got from ordinary measurement. In GaAs quantum dots and graphene quantum dots,we studied the reflectome-try measurement. With the help of high bandwidth,we developed a fast readout technique that orders higher speed than ordinary measurement methods. 5.Introduced the Landau-Zener transition in a semiconductor single electron charge qubit formed by semiconductor double quantum dots. From two-level-system, we studied the basic physics of Landau-Zener transition, and Landau-Zener-Stuckelberg interference which come from multi-passage Landau-Zener transition. In semi-conductor charge qubit, we studied the Landau-Zener transition and phase accu-mulation in multi-passage interference. With the help of controllable pulse, we could manipulate the single electron charge qubit to rotate on Bloch sphere with arbitrary position, in another word, the universal control of the single electron charge qubit.6. Demonstrate a proof-of-principle quantum simulation of Kibble-Zurek mecha-nism using a single electron charge qubit in double quantum dot, set to behave as a Landau-Zener dynamics. From equilibrium phase transition, we introduced the non-equilibrium phase transition and Kibble-Zurek mechanism. Kibble-Zurek mechanism predicted the production of topological structure in symmetry break-ing phase transition. Landau-Zener transition is a simplest quantum model ex-hibiting the key physics of Kibble-Zurek mechanism.7. Summarized the above experimental work, and emphasized the importance of our work. Gave the suggestions of improvements and perspective of future experi-mental research.The main innovations of this thesis are:1. Studied the technique of radio-frequency reflectometry measurement. This mea-surement method provides higher bandwidth and sensitivity that ordinary mea-surement method cannot reach. From reflectometry circuit, we discussed the principle of this method, and compared the data got from ordinary measurement. In GaAs quantum dots and graphene quantum dots, we studied the reflectome-try measurement. With the help of high bandwidth, we developed a fast readout technique that orders higher speed than ordinary measurement methods.2. With the help of controllable pulse, using Landau-Zener transition we could ma-nipulate the single electron charge qubit to rotate on Bloch sphere with arbitrary position, in another word, the universal control of the single electron charge qubit.3. Implemented a proof-of-principle quantum simulation of a tunable non-equilibrium second order phase transition. We have demonstrated that the simulated dynam- ics for the topological effect formation shows a function of quench rate, one of the natural features of the Kibble-Zurek mechanism.