The nitrogen-vacancy (N-V) center in diamond is a widely-used platform for quantum information processing and metrology. The electron-spin state of N-V center could be initialized and readout optically, and manipulated by resonate microwave fields. In this work, we analyze the dependence of electron-spin initialization on widths of laser pulses. We build a numerical model to simulate this process and verify the simulation results in experiment. Both simulations and experiments reveal a fact that shorter laser pulses are helpful to the electron-spin polarization. We therefore propose to use extremely-short laser pulses for electron-spin initialization. In this new scheme, the spin-state contrast could be improved about 10% in experiment by using laser pulses as short as 4 ns in width. Furthermore, we provide a mechanism to explain this effect which is due to the occupation time in the meta-stable spin-singlet states of N-V center. Our new scheme is applicable in a broad range of NV-based applications in the future.

中文翻译：

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金刚石中光学泵浦 NV 电子自旋的脉冲宽度诱导极化增强

金刚石中的氮空位 (NV) 中心是一种广泛使用的量子信息处理和计量平台。NV中心的电子自旋状态可以通过光学方式初始化和读出，并通过共振微波场进行操纵。在这项工作中，我们分析了电子自旋初始化对激光脉冲宽度的依赖性。我们建立了一个数值模型来模拟这个过程并在实验中验证模拟结果。模拟和实验都揭示了一个事实，即较短的激光脉冲有助于电子自旋极化。因此，我们建议使用极短的激光脉冲进行电子自旋初始化。在这个新方案中，通过使用宽度短至 4 ns 的激光脉冲，实验中的自旋状态对比度可以提高约 10%。此外，我们提供了一种机制来解释这种效应，这是由于 NV 中心的亚稳态自旋单线态中的占据时间。我们的新方案将来适用于广泛的基于 NV 的应用程序。