Precisely and efficiently designing control pulses for the preparation of quantum states and quantum gates are the fundamental tasks for quantum computation.Gradient-based optimal control methods are the routine to de...Precisely and efficiently designing control pulses for the preparation of quantum states and quantum gates are the fundamental tasks for quantum computation.Gradient-based optimal control methods are the routine to design such pulses.However,the gradient information is often difficult to calculate or measure,especially when the system is not well calibrated or in the presence of various uncertainties.Gradient-free evolutionary algorithm is an alternative choice to accomplish this task but usually with low-efficiency.Here,we design an efficient mutation rule by using the information of the current and the former individuals together.This leads to our improved differential evolution algorithm,called da DE.To demonstrate its performance,we numerically benchmark the pulse optimization for quantum states and quantum gates preparations on small-scale NMR system.Further numerical comparisons with conventional differential evolution algorithms show that da DE has great advantages on the convergence speed and robustness to several uncertainties including pulse imperfections and measurement errors.展开更多
The dynamical decoupling(DD) method is widely adopted to preserve coherence in different quantum systems. In the case of ideal pulses, its effects on the suppression of noise can be analytically described by the mathe...The dynamical decoupling(DD) method is widely adopted to preserve coherence in different quantum systems. In the case of ideal pulses, its effects on the suppression of noise can be analytically described by the mathematical form of filter function. However, in practical experiments, the unavoidable pulse errors limit the efficiency of DD. In this paper,we study the effects of imperfect pulses on DD efficiency based on quantum trajectories. By directly generating a pseudo noise sequence correlated in time, we can explore the performance of DD with different pulse errors in the typical noise environment. It shows that, for the typical 1/f noise environment, the phase error of operational pulses severely affects the performance of noise suppression, while the detuning and intensity errors have less influence. Also, we get the thresholds of these errors for efficient DD under the given experimental conditions. Our method can be widely applied to guide practical DD experimental implementation.展开更多
基金supported by the National Natural Science Foundation of China(11605005,11875159,and U1801661)Science,Technology and Innovation Commission of Shenzhen Municipality(ZDSYS20170303165926217 and JCYJ20180302174036418)+4 种基金Guangdong Innovative and Entrepreneurial Research Team Program(2016ZT06D348)supported by the National Key Research and Development Program of China(2018YFA0306600)the National Science Fund for Distinguished Young Scholars(11425523)Projects of International Cooperation and Exchanges NSFC(11661161018)Anhui Initiative in Quantum Information Technologies(AHY050000)
文摘Precisely and efficiently designing control pulses for the preparation of quantum states and quantum gates are the fundamental tasks for quantum computation.Gradient-based optimal control methods are the routine to design such pulses.However,the gradient information is often difficult to calculate or measure,especially when the system is not well calibrated or in the presence of various uncertainties.Gradient-free evolutionary algorithm is an alternative choice to accomplish this task but usually with low-efficiency.Here,we design an efficient mutation rule by using the information of the current and the former individuals together.This leads to our improved differential evolution algorithm,called da DE.To demonstrate its performance,we numerically benchmark the pulse optimization for quantum states and quantum gates preparations on small-scale NMR system.Further numerical comparisons with conventional differential evolution algorithms show that da DE has great advantages on the convergence speed and robustness to several uncertainties including pulse imperfections and measurement errors.
基金Project supported by the National Basic Research Program of China(Grant No.2016YFA0301903)the National Natural Science Foundation of China(Grant Nos.11174370,11304387,61632021,11305262,and 61205108)the Research Plan Project of the National University of Defense Technology(Grant No.ZK16-03-04)
文摘The dynamical decoupling(DD) method is widely adopted to preserve coherence in different quantum systems. In the case of ideal pulses, its effects on the suppression of noise can be analytically described by the mathematical form of filter function. However, in practical experiments, the unavoidable pulse errors limit the efficiency of DD. In this paper,we study the effects of imperfect pulses on DD efficiency based on quantum trajectories. By directly generating a pseudo noise sequence correlated in time, we can explore the performance of DD with different pulse errors in the typical noise environment. It shows that, for the typical 1/f noise environment, the phase error of operational pulses severely affects the performance of noise suppression, while the detuning and intensity errors have less influence. Also, we get the thresholds of these errors for efficient DD under the given experimental conditions. Our method can be widely applied to guide practical DD experimental implementation.
