Research On The Spectrum Structure And Quantum Gate Of Superconducting CQED System

As a kind of parameter controllable artificial atom,superconducting qubit is the based unit of constructing a superconducting quantum computer,and it also can be used as a quantum optics effect platform.To achieve superconducting quantum computation,we need to characterize the single qubit and qubit-qubit coupling features.In this thesis,we have focused on the simulation,fabrication process and testing of three-dimensional(3D)Transmon qubit.In this cavity quantum electrodynamics(CQED)system,we have comprehensively measured the transition spectrum structure,coherence property and single bit quantum gate in detail.By coupled two qubits with a 3D cavity,a kind of two-bit quantum gate has been realized.First,we investigated in the fabrication process of qubits on sapphire substrate based on double angle evaporation technique,especially detail in the edge defects,Josephson junction defined and oxide parameter control problem.Then we tested the single qubit in a dilution refrigerator,having observed single photon and multi-photon transition spectrum,photon number splitting effect and ac-Stark effect.High energy level coherence and decay features have been studied in our system,and the single qubit gate around x and y axis is also realized.At last,using the Cliffords randomized benchmarking,we have characterized the fidelity of single bit quantum gates.Using the superconducting quantum circuit as a quantum optics effect platform,we have studied the Aulter-Townes Splitting(ATS)effect and electromagnetically induced transparency(EIT)effect.Under different decay rate and control tone condition,the transition between ATS effect and EIT effect has been confirmed by Born-Markov master equation and Akaike Information Criterion(AIC)theory.Also,by applying a control tone between the second excited level and cavity dispersive level,we can construct a Ladder type quantum three level system and investigate the quantum coherent effect between qubit and cavity.A kind of controllable coupling scheme can be realized with this coherent effect.In addition,we have used a 3D cavity to couple two Transmon qubit by virtual photon process and observed the anti-crossing phenomenon in system spectrum,because of the couple between two qubits.Using the ac-Stark effect to realized two bit quantum state swap gate.In addition,a kind of two photon process Rabi-like oscillation has been realized between |00| and |11| and it also can be used to construct two-bit quantum gate.