The recently developed magic-intensity trapping technique of neutral atoms efficiently mitigates the detrimental effect of light shifts on atomic qubits and substantially enhances the coherence time. This technique re...The recently developed magic-intensity trapping technique of neutral atoms efficiently mitigates the detrimental effect of light shifts on atomic qubits and substantially enhances the coherence time. This technique relies on applying a bias magnetic field precisely parallel to the wave vector of a circularly polarized trapping laser field. However, due to the presence of the vector light shift experienced by the trapped atoms, it is challenging to precisely define a parallel magnetic field, especially at a low bias magnetic field strength, for the magic-intensity trapping of85Rb qubits. In this work, we present a method to calibrate the angle between the bias magnetic field and the trapping laser field with the compensating magnetic fields in the other two directions orthogonal to the bias magnetic field direction. Experimentally, with a constantdepth trap and a fixed bias magnetic field, we measure the respective resonant frequencies of the atomic qubits in a linearly polarized trap and a circularly polarized one via the conventional microwave Rabi spectra with different compensating magnetic fields and obtain the corresponding total magnetic fields via the respective resonant frequencies using the Breit–Rabi formula. With known total magnetic fields, the angle is a function of the other two compensating magnetic fields.Finally, the projection value of the angle on either of the directions orthogonal to the bias magnetic field direction can be reduced to 0(4)° by applying specific compensating magnetic fields. The measurement error is mainly attributed to the fluctuation of atomic temperature. Moreover, it also demonstrates that, even for a small angle, the effect is strong enough to cause large decoherence of Rabi oscillation in a magic-intensity trap. Although the compensation method demonstrated here is explored for the magic-intensity trapping technique, it can be applied to a variety of similar precision measurements with trapped neutral atoms.展开更多
采用熔化极气体保护电弧(Gas metal arc,GMA)作为热源,以H08Mn2Si焊丝作为填充材料,开展了多层单道薄壁构件堆积层尺寸特征研究。借助金相显微镜测量了堆积层尺寸,分析了堆积层尺寸特性并阐明其成形机制。结果表明,堆积层尺寸在前四层...采用熔化极气体保护电弧(Gas metal arc,GMA)作为热源,以H08Mn2Si焊丝作为填充材料,开展了多层单道薄壁构件堆积层尺寸特征研究。借助金相显微镜测量了堆积层尺寸,分析了堆积层尺寸特性并阐明其成形机制。结果表明,堆积层尺寸在前四层处于不稳定状态,波动较大。随堆积层数的增加,堆积层层高逐渐减小并趋于稳定,堆积层层宽先减小,随后逐渐增大并趋于稳定,层宽在第二个堆积层具有极小值。进一步设计了二次回归旋转组合试验方法,采集的试验数据作为训练样本,基于神经网络算法建立了堆积工艺参数(堆积电流、行走速度、堆积电压)与堆积层尺寸的非线性模型,经测试数据样本验证表明,模型预测精度较高,堆积层尺寸预测最大相对误差小于6.98%。根据堆积层尺寸预测模型,进行了封闭路径与非封闭路径薄壁构件的堆积成形,试验结果表明,该模型能够应用于薄壁构件GMA增材制造自适应分层切片过程。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12104414,12122412,12104464,and 12104413)the China Postdoctoral Science Foundation(Grant No.2021M702955).
文摘The recently developed magic-intensity trapping technique of neutral atoms efficiently mitigates the detrimental effect of light shifts on atomic qubits and substantially enhances the coherence time. This technique relies on applying a bias magnetic field precisely parallel to the wave vector of a circularly polarized trapping laser field. However, due to the presence of the vector light shift experienced by the trapped atoms, it is challenging to precisely define a parallel magnetic field, especially at a low bias magnetic field strength, for the magic-intensity trapping of85Rb qubits. In this work, we present a method to calibrate the angle between the bias magnetic field and the trapping laser field with the compensating magnetic fields in the other two directions orthogonal to the bias magnetic field direction. Experimentally, with a constantdepth trap and a fixed bias magnetic field, we measure the respective resonant frequencies of the atomic qubits in a linearly polarized trap and a circularly polarized one via the conventional microwave Rabi spectra with different compensating magnetic fields and obtain the corresponding total magnetic fields via the respective resonant frequencies using the Breit–Rabi formula. With known total magnetic fields, the angle is a function of the other two compensating magnetic fields.Finally, the projection value of the angle on either of the directions orthogonal to the bias magnetic field direction can be reduced to 0(4)° by applying specific compensating magnetic fields. The measurement error is mainly attributed to the fluctuation of atomic temperature. Moreover, it also demonstrates that, even for a small angle, the effect is strong enough to cause large decoherence of Rabi oscillation in a magic-intensity trap. Although the compensation method demonstrated here is explored for the magic-intensity trapping technique, it can be applied to a variety of similar precision measurements with trapped neutral atoms.
文摘采用熔化极气体保护电弧(Gas metal arc,GMA)作为热源,以H08Mn2Si焊丝作为填充材料,开展了多层单道薄壁构件堆积层尺寸特征研究。借助金相显微镜测量了堆积层尺寸,分析了堆积层尺寸特性并阐明其成形机制。结果表明,堆积层尺寸在前四层处于不稳定状态,波动较大。随堆积层数的增加,堆积层层高逐渐减小并趋于稳定,堆积层层宽先减小,随后逐渐增大并趋于稳定,层宽在第二个堆积层具有极小值。进一步设计了二次回归旋转组合试验方法,采集的试验数据作为训练样本,基于神经网络算法建立了堆积工艺参数(堆积电流、行走速度、堆积电压)与堆积层尺寸的非线性模型,经测试数据样本验证表明,模型预测精度较高,堆积层尺寸预测最大相对误差小于6.98%。根据堆积层尺寸预测模型,进行了封闭路径与非封闭路径薄壁构件的堆积成形,试验结果表明,该模型能够应用于薄壁构件GMA增材制造自适应分层切片过程。
