The achievable precision of parameter estimation plays a significant role in evaluating a strategy of metrology.In practice,one may employ approximations in a theoretical model development for simplicity,which,however...The achievable precision of parameter estimation plays a significant role in evaluating a strategy of metrology.In practice,one may employ approximations in a theoretical model development for simplicity,which,however,will cause systematic error and lead to a loss of precision.We derive the error of maximum likelihood estimation in the weak-value amplification technique where the linear approximation of the coupling parameter is used.We show that this error is positively related to the coupling strength and can be effectively suppressed by improving the Fisher information.Considering the roles played by weak values and initial meter states in the weak-value amplification,we also point out that the estimation error can be decreased by several orders of magnitude by averaging the estimations resulted from different initial meter states or weak values.These results are finally illustrated in a numerical example where an extended linear response regime to the parameter is observed.展开更多
We experimentally demonstrate the quantum anti-Zeno effect in a two-level system based on a single trapped ion ^（40）Ca~＋. In the large detuning regime, we show that the transfer from the ground state to the excited...We experimentally demonstrate the quantum anti-Zeno effect in a two-level system based on a single trapped ion ^（40）Ca~＋. In the large detuning regime, we show that the transfer from the ground state to the excited state can be remarkably enhanced by the inserted projection measurements. The inserted measurements in our experiment are realized by the electron shelving technique. Compared to the ideal projection measurement, which makes the quantum state collapse instantaneously, a practical electron shelving process needs a finite time duration. The minimum time for this collapse process is shown to be inversely proportional to the square of the coupling strength between the measurement laser and the system.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 Innovation Program for Quantum Science and Technology (Grant No.2021ZD0301601)the Science and Technology Innovation Program of Hunan Province (Grant No.2022RC1194)the National Natural Science Foundation of China (Grant Nos.11904402,12074433,12004430,12174447,12204543,and 12174448)。
文摘The achievable precision of parameter estimation plays a significant role in evaluating a strategy of metrology.In practice,one may employ approximations in a theoretical model development for simplicity,which,however,will cause systematic error and lead to a loss of precision.We derive the error of maximum likelihood estimation in the weak-value amplification technique where the linear approximation of the coupling parameter is used.We show that this error is positively related to the coupling strength and can be effectively suppressed by improving the Fisher information.Considering the roles played by weak values and initial meter states in the weak-value amplification,we also point out that the estimation error can be decreased by several orders of magnitude by averaging the estimations resulted from different initial meter states or weak values.These results are finally illustrated in a numerical example where an extended linear response regime to the parameter is observed.
基金Project supported by the National Basic Research Program of China(Grant No.2016YFA0301903)the National Natural Science Foundation of China(Grant Nos.11174370,11304387,61632021,11305262,11574398,and N 61205108)the Research Plan Project of National University of Defense Technology,China(Grant No.ZK16-03-04)
文摘We experimentally demonstrate the quantum anti-Zeno effect in a two-level system based on a single trapped ion ^（40）Ca~＋. In the large detuning regime, we show that the transfer from the ground state to the excited state can be remarkably enhanced by the inserted projection measurements. The inserted measurements in our experiment are realized by the electron shelving technique. Compared to the ideal projection measurement, which makes the quantum state collapse instantaneously, a practical electron shelving process needs a finite time duration. The minimum time for this collapse process is shown to be inversely proportional to the square of the coupling strength between the measurement laser and the system.
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.
