We propose to employ a recurrent neural network to estimate a fluctuating magnetic field from continuous optical Faraday rotation measurement on an atomic ensemble. We show that an encoder-decoder architecture neural network can process measurement data and learn an accurate map between recorded signals and the time-dependent magnetic field. The performance of this method is comparable to Kalman filters while it is free of the theory assumptions that restrict their application to particular measurements and physical systems.
Optimal waveform estimation for classical and quantum systems via time-symmetric smoothing. II. Applications to atomic magnetometry and Hardy's paradox
量子平滑理论[Tsang，Phys. Rev. Lett. 102，250403（2009）; Phys. Rev. A，印刷中（电子印刷arXiv：0906.4133）]被扩展以解释待估计的经典随机过程中的离散跳跃、量子系统中的离散变量，例如自旋、角动量和光子数，以及泊松测量，例如光子计数。应用扩展理论对原子磁力计进行了建模，并研究了相空间中的哈代佯谬。在哈代提出的实验的相空间图像中，预测的维格纳分布的负性被认为是经典推理和量子力学之间不一致的罪魁祸首。
Level-crossing (LC) resonances in a buffer-gas-filled cesium vapor cell are studied under counterpropagating pump and probe light waves with opposite circular polarizations. The waves excite the D$_1$-line ground-state level $F_g$$=\,$$4$, while a transverse magnetic field (${\rm B}_x$$\perp$${\rm k}$) is scanned around zero to observe the resonance of electromagnetically induced absorption (EIA). It is shown that adding the pump light wave significantly improves the properties of the resonances in comparison with the commonly used scheme with a single light wave. As far as a small vapor cell …
Atomic magnetometers are highly sensitive detectors of magnetic fields that monitor the evolution of the macroscopic magnetic moment of atomic vapors, and opening new applications in biological, physical, and chemical science. However, the performance of atomic magnetometers is often limited by hidden systematic effects that may cause misdiagnosis for a variety of applications, e.g., in NMR and in biomagnetism. In this work, we uncover a hitherto unexplained interference effect in atomic magnetometers, which causes an important systematic effect to greatly deteriorate the accuracy of measuring…
Quantum sensors typically translate external fields into a periodic response whose frequency is then determined by analyses performed in Fourier space. This allows for a linear inference of the parameters that characterize external signals. In practice, however, quantum sensors are able to detect fields only in a narrow range of amplitudes and frequencies. A departure from this range, as well as the presence of significant noise sources and short detection times, lead to a loss of the linear relationship between the response of the sensor and the target field, thus limiting the working regime …
Learning unified control of intrinsic nonlinear spin dynamics in atomic qudits for magnetometry
College of Physics, Nanjing University of Aeronautics（南京航空航天大学物理学院）；China Mobile (Suzhou) Software Technology Co., Ltd.（中国移动（苏州）软件技术有限公司）；Shanghai Institute of Optics and Fine Mechanics（上海光学精密机械研究所）；Chinese Academy of Sciences（中国科学院）；Key Laboratory of Aerospace Information Sensing（航空航天信息感知重点实验室）
Continuously monitored atomic spin-ensembles allow, in principle, for real-time sensing of external magnetic fields beyond classical limits. Within the linear-Gaussian regime, thanks to the phenomenon of measurement-induced spin-squeezing, they attain a quantum-enhanced scaling of sensitivity both as a function of time, $t$, and the number of atoms involved, $N$. In our work, we rigorously study how such conclusions based on Kalman filtering methods change when inevitable imperfections are taken into account: in the form of collective noise, as well as stochastic fluctuations of the field in t…
Shallow Nitrogen-Vacancy (NV) centers are promising candidates for high-precision sensing applications; these defects, when positioned a few nanometers below the surface, provide an atomic-scale resolution along with substantial sensitivity. However, the dangling bonds and impurities on the diamond surface result in a complex environment which reduces the sensitivity and is unique to each shallow NV center. To avoid the environment's detrimental effect, we apply feedback-based quantum optimal control. We first show how a direct search can improve the initialization/readout process. In a second…
A scheme of an ultra-sensitive magnetometer in the cavity quantum electromagnonics where the intracavity microwave mode coupled to a magnonic mode via magnetic dipole interaction is proposed. It is shown that by driving both magnonic and microwave modes with external classical fields and controlling the system parameters, one can reduce the added noise of magnetic field measurement below the standard quantum limit (SQL). Surprisingly, we show that beyond the rotating wave approximation (RWA), not only the added noise can be suppressed, but also the output cavity response to the input signal ca…
Heisenberg scaling in optical magnetometry with measurement-induced correlations as a quantum resource
International Quantum Academy, Shenzhen（国际量子科学院）；Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen（南方科技大学深圳量子科学与工程研究院）；Department of Physics, Southern University of Science and Technology, Shenzhen（南方科技大学物理系）；Department of Physics, Zhejiang University of Science and Technology, Hangzhou（浙江科技学院物理系）
Isofrequency spin-wave imaging using color center magnetometry for magnon spintronics
Delft University of Technology（代尔夫特理工大学）；Heriot-Watt University（赫瑞-瓦特大学）；Kansas State University（堪萨斯州立大学）；Université de Montpellier and CNRS（蒙彼利埃大学与法国国家科学研究中心）
Entanglement-enhanced optical magnetometry beyond the standard quantum limit
Niels Bohr Institute, University of Copenhagen（尼尔斯·玻尔研究所，哥本哈根大学）；Institut Langevin, ESPCI Paris, Université PSL, Sorbonne Université, Université Paris Cité, CNRS（朗之万研究所，巴黎高等物理化工学院，巴黎文理研究大学，索邦大学，巴黎西岱大学，法国国家科学研究中心）；INFN, Sezione di Padova（意大利国家核物理研究所，帕多瓦分部）
Planar squeezing by quantum non-demolition measurement in cold atomic ensembles
平面压缩态，即在两个正交自旋分量中压缩的量子态，由于其在原子干涉和量子信息中的应用，近年来引起了人们的关注[Q. Y. He等人，New J.Phys.14，093012（2012）]。虽然正则变量，如辐射场的平方可以压缩在最多一个分量，同时压缩在两个正交的自旋分量可以实现由于角动量对易关系。提出了一种利用量子非破坏（QND）测量自旋为1的系统平面压缩的新方案。QND测量是通过近共振顺磁法拉第旋转探测实现的，而平面压缩是通过两个正交自旋分量的顺序QND测量获得的。我们计算了各种光学深度，初始条件和探测策略的可实现的压缩。以这种方式产生的平面压缩态包含可通过自旋压缩不等式检测的纠缠，并且对于任何进动相位角，相对于非压缩态都具有优势，有利于单次和高带宽磁力测量。
Magnetically Induced Transparency-Absorption and Normal-Anomalous Dispersion Characteristics of ${}^{87}\text{Rb}$ Medium or Any J-Type Configuration Atomic Vapors Subject to a Vector Magnetic Field and a Weak Resonant Pump
Alikhanyan National Laboratory (Yerevan Physics Institute)（阿利哈尼扬国家实验室（耶烈万物理研究所））；Institute for Physical Research, Armenian National Academy of Sciences（亚美尼亚国家科学院物理研究所）
