The Quantum Information Processing In Circuit QED System Is Realized By Using Superadiabatic-based Shortcut

Because of its expansibility and ease of operation,superconducting qubits become one of the most likely solutions to realize quantum computing.The circuit quantum electrodynamics(circuit QED)system provides a simple and reliable way to control and measure superconducting qubits.Superadiabatic-based shortcut is an improved adiabatic algorithm,it does not need to meet the adiabatic condition,and restrains unnecessary transition between different eigenstates in the system through the adiabatic drive,therefore,it not only effectively reduces the system control time,but also reduces the error influenced by dissipation due to the decoherence of qubits and physical system.In this thesis,we study the quantum information processing based on the superadiabatic-based shortcut algorithm in the circuit quantum electrodynamics system.The main work and results are as follows:Firstly,in order to solve the problem that the adiabatic algorithm takes a long operation time in the process of system evolution,we propose a fast multi-qubit entangled state preparation scheme based on the superadiabatic-based shortcut algorithm.In circuit QED system,the effective Hamiltonian of the system is modified by using the superadiabatic-based shortcut method to accelerate the evolution process.At first,the process of producing the maximum entangled state of two qubits is given,and then the preparation of three qubits(W state)is given,together with the extension to the preparation of the entangled state of many qubits(the number of qubits is greater than 4).Their theoretical derivation and corresponding numerical simulation based on the superadiabatic-based shortcut algorithm are discussed.The results show that in circuit QED system,multi-qubit entangled states can be prepared rapidly based on the superadiabatic-based shortcut algorithm.When the number of qubits is odd,the derivation of the effective Hamiltonian involved is simpler and easier to realize.At the same time,the time required to prepare the W state of the proposed scheme is 50 nanoseconds,which is 1/12 of that in [22],and the evolution time is shorter and has acceleration.The decoherence process of the system is described and evaluated by the master equation,and the final fidelity is always above 0.98,which indicates that the scheme is effective and robust.Secondly,based on the characteristics of the phase gate in quantum computing,we propose a fast phase gate preparation scheme based on the super adiabatic shortcut algorithm.The preparation of one qubit phase gate and two qubit controlled phase gate are given respectively.The energy levels of the qubit are coded as |0(?) and |1(?),and the effective Hamiltonian of the system is obtained by classifying different initial states.After two iterations using the superadiabatic-based shortcut algorithm,the correction term of the same form as the system effective Hamiltonian is obtained to suppress the transitions between other eigenstates.According to the evolution path,the appropriate boundary conditions are obtained to complete the preparation of the control phase gate.The numerical simulation results show that the -|1(?)(-|11(?))state can be obtained by system evolution when the initial state is |1(?)(|11(?)),while the system evolution does not change at all when the other initial states are used.And the final fidelity of the phase gate is close to 1.Finally,through the analysis of the influence of the cavity leakage,the spontaneous emission of qubit and the phasing out,the final fidelity of the system is always maintained above 0.984 to assure the system's robustness and stability.