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arXiv 2312.12643quant-phcond-mat.mtrl-sci
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金刚石中暗自旋的磁噪声功率谱表征

Characterizing the magnetic noise power spectrum of dark spins in diamond

Ethan Q. Williams, Chandrasekhar Ramanathan

AI总结:

本文针对固态自旋量子比特相干时间受暗自旋浴限制的问题,用pEPR-CPMG动态解耦技术直接测量金刚石P1中心磁噪声功率谱,揭示其特征并开发高频表征技术,为量子金刚石制备及纳米磁测量提供支撑。

摘要:

固态平台中自旋量子比特的相干时间常受自旋浴的限制。尽管这些通常为暗浴自旋的部分性质可通过中心量子比特间接表征,但通过直接测量表征其性质至关重要。本文使用基于脉冲电子顺磁共振(pEPR)的卡尔-珀塞尔-迈博姆-吉尔(CPMG)动态解耦技术,测量了金刚石中P1(替代氮)中心系综的磁噪声功率谱,这些中心通常构成NV(氮-空位)中心的浴。针对P1中心的实验在低[N]化学气相沉积(CVD)样品和高[N]高温高压(HPHT)样品上于89 mT下进行,后者的NV中心使用同一2.5 GHz pEPR谱仪表征。所有功率谱均显示两个明显特征:一个近似按1/ω^0.7-1.0缩放的宽分量,以及一个位于^13C拉莫尔频率处的显著峰。宽分量的行为与P1中心聚类导致的洛伦兹谱非均匀分布一致,该聚类最近被证明在HPHT金刚石中普遍存在,而CVD金刚石中是否存在此类聚类尚不清楚。我们开发了利用CPMG滤波函数谐波的技术以改进高频信号表征,并在^13C核拉莫尔频率上进行了演示,在190 mT下该频率为2.04 MHz,是CPMG调制频率(硬件限制下<357 kHz)的5.7倍。我们评估了方法在有限脉冲宽度和翻转角误差存在时的鲁棒性。理解暗自旋的相互作用将为量子技术的金刚石制备方法提供参考,这些技术适用于纳米级核磁共振和化学传感的交流磁测量。

英文摘要:

Coherence times of spin qubits in solid-state platforms are often limited by the presence of a spin bath. While some properties of these typically dark bath spins can be indirectly characterized via the central qubit, it is important to characterize their properties by direct measurement. Here we use pulsed electron paramagnetic resonance (pEPR) based Carr-Purcell-Meiboom-Gill (CPMG) dynamical decoupling to measure the magnetic noise power spectra for ensembles of P1 (substitutional nitrogen) centers in diamond that typically form the bath for NV (nitrogen-vacancy) centers. The experiments on the P1 centers were performed on a low [N] CVD (chemical vapor deposition) sample and a high [N] HPHT (high-temperature, high-pressure) sample at 89 mT. We characterize the NV centers of the latter sample using the same 2.5 GHz pEPR spectrometer. All power spectra show two distinct features, a broad component that is observed to scale as approximately $1/ω^{0.7-1.0}$, and a prominent peak at the $^{13}$C Larmor frequency. The behavior of the broad component is consistent with an inhomogeneous distribution of Lorentzian spectra due to clustering of P1 centers, which has recently been shown to be prevalent in HPHT diamond. It is unknown if such clustering occurs in CVD diamond. We develop techniques utilizing harmonics of the CPMG filter function to improve characterization of high-frequency signals, which we demonstrate on the $^{13}$C nuclear Larmor frequency. At 190 mT this is 2.04 MHz, 5.7 times higher than the CPMG modulation frequency ($<357$ kHz, hardware-limited). We assess the robustness of our methods in the presence of finite pulse widths and flip angle errors. Understanding the interactions of dark spins will inform methods of diamond fabrication for quantum technology. These techniques are applicable to ac magnetometry for nanoscale nuclear magnetic resonance and chemical sensing.

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