发表机构
Institute of Science Tokyo; National Institute for Materials Science; University of Tsukuba; National Institutes for Quantum Science and Technology : QST; Tohoku University（科学技术研究所; 国立材料研究所; 筑波大学; 量子科学技术研究开发机构; 东北大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究提出双反馈方案补偿双量子4-Ramsey干涉仪中的频率偏移，实现长期稳定的金刚石量子磁力计，灵敏度达7.0 pT/Hz^1/2，噪声底64 fT/Hz^1/2，适用于微弱生物磁信号检测。
AI 中文摘要
我们通过集成一个双反馈系统，该系统补偿双量子（DQ）4-Ramsey干涉仪中的共模和差模频率偏移，开发了一种高灵敏度且长期稳定的金刚石量子磁力计。检测极弱的磁场信号需要大量的信号累积以增强信噪比。然而，由热漂移或环境磁噪声引起的最优工作频率的偏差严重阻碍了此类传感系统的长期稳定性。为克服这一限制，我们首先基于包含失谐的哈密顿量推导了信号对共模和差模失谐的解析解，以从理论上阐明DQ 4-Ramsey传感中的鲁棒性极限。在该理论模型的指导下，我们引入了同步频率调制和双反馈方案，以独立跟踪并补偿这些频率偏移，同时保持最优的磁场响应。所提出的方法使得在2.8 K的温度变化下能够稳定连续运行。通过在5-100 Hz频率范围内维持7.0 pT/Hz^1/2的磁场灵敏度长达4小时，我们实现了64 fT/Hz^1/2的极低噪声底。在长时间连续传感过程中，系统表现出预期的与积分时间T的1/T^1/2标度关系，并防止了振幅低估和波形失真。这些结果为长期DQ 4-Ramsey金刚石磁力测定建立了一种鲁棒方法，并展示了其检测微弱生物磁信号的潜力。
英文摘要
We developed a highly sensitive and long-term stable diamond quantum magnetometer by integrating a dual-feedback system that compensates for common- and differential-mode frequency shifts in double-quantum (DQ) 4-Ramsey interferometry. Detecting extremely weak magnetic-field signals requires extensive signal accumulation to enhance the signal-to-noise ratio. However, deviations from the optimal operating frequencies caused by thermal drift or environmental magnetic noise severely hinder the long-term stability of such a sensing system. To overcome the limitation, we first derived analytical solutions for the signal response to common- and differential-mode detunings based on a detuning-inclusive Hamiltonian to theoretically clarify the robustness limit in DQ 4-Ramsey sensing. Guided by this theoretical model, we introduced synchronized frequency modulation and a dual-feedback scheme to independently track and compensate for these frequency shifts while maintaining an optimal magnetic-field response. The proposed method enabled stable continuous operation against temperature variations of 2.8 K. By maintaining a magnetic field sensitivity of 7.0 pT/Hz^1/2 in the frequency range of 5-100 Hz for a prolonged duration of 4 hours, we achieved an extremely low noise floor of 64 fT/Hz^1/2. During prolonged continuous sensing, the system exhibited the expected 1/T^1/2 scaling with integration time T, and prevented both the underestimation of amplitude and waveform distortion. These results establish a robust approach for long-term DQ 4-Ramsey diamond magnetometry and demonstrate its potential for detecting weak biomagnetic signals.
