含驱动外场的超导量子比特退相干问题研究

Research on Decoherence of Superconducting Qubits with Driving External Field

摘要: 超导量子比特的退相干效应是量子计算发展的主要障碍之一。本文基于最新超导量子比特实验参数(T₁ = 200 μs, T₂ = 300 μs)，通过求解含驱动场的主方程，得到了系统的稳态解，分析了量子态的退相干动力学过程。本文进一步采用4~5阶龙格—库塔法数值求解Bloch方程，并计算得到在当前高保真度门操作时间10 ns内，退相干效应的影响已显著降低(态保真度 > 99.7%)。通过计算发现，驱动外场频率与量子比特固有振动频率的失谐，能够有效保护量子比特的相干性。

Abstract: The decoherence effect of superconducting qubits is one of the main obstacles to the development of quantum computing. Based on the latest experimental parameters of superconducting qubits (T₁ = 200 μs, T₂ = 300 μs), the steady-state solution of the system is obtained by solving the master equation with the driving field, and the decoherence dynamics of the quantum state is analyzed. In this paper, the 4~5 order Runge Kutta method is further used to numerically solve the Bloch equation, and it is calculated that the influence of decoherence effect has been significantly reduced (state fidelity > 99.7%) within 10 ns of the current high fidelity gate operation time. It is found that the detuning between the driving external field frequency and the natural vibration frequency of the qubit can effectively protect the coherence of the qubit.