Coherent Time Extension Of Ion Qubit Based On Dynamical Decoupling

The limited coherence time of qubits is one of the major obstacles to the realization of quantum computing.The dynamic decoupling method is one widely used approach to maintain the coherence of qubits.The main idea of this method is to introduce the periodic external control field,partially offset the interaction Hamiltonian between the quantum system and the environment,and preserve the coherence of qubits.The theme of this paper is focused on the application of dynamic decoupling method on the coherence maintainance of ion qubits.Firstly,this paper introduces the basic principle of dynamic decoupling method,discusses its effects on ion qubits' dephasing suppression in different noise environment and points out the key of dynamic decoupling application is the appropriate matching between dynamical decoupling sequence and environmental noise power spectrum.Secondly,based on the power spectrum information of environmental noise and the effect of dynamic decoupling sequence,the paper discusses how to use the dynamic decoupling method to detect and split noise power spectrum and how the imperfections of pulses influence the decoupling effects.In this paper,a simulation tool is built to study the effect of various imperfect pulses on the ion qubit dephasing process under set experimental conditions,and the error thresholds of imperfect pulses are obtained.In addition,ion qubit can be used as noise sensor using the dynamic decoupling method.In particular,due to the different sensitivity of calcium ions to magnetic noise,calcium ions can be used to detect and separate the power spectral density of magnetic noise and understand the information of environmental noise.Through the theory and simulation study of dynamic decoupling application,the experiment can be guided better to suppress the dephasing.