We develop and demonstrate a new protocol that allows sensing of magnetic fields in an extra-ordinary regime for atomic magnetometry. Until now, the demonstrated bandwidth for atomic magnetometry has been constrained to be slower than the natural precession of atomic spins in a magnetic field---the Larmor frequency. We demonstrate a new approach that tracks the instantaneous phase of atomic spins to measure arbitrarily modulated magnetic fields with frequencies up to fifty times higher than the Larmor frequency. By accessing this regime, we demonstrate magnetic-field measurements across four decades in frequency up to 400 kHz, over three orders of magnitude wider than conventional atomic magnetometers. Furthermore, we demonstrate that our protocol can linearly detect transient fields 100--fold higher in amplitude than conventional methods. We highlight the bandwidth and dynamic range of the technique by measuring a magnetic field with a broad and dynamical spectrum.
Broadband Rydberg Atomic Microwave Sensing with 44.6$\,$MHz Instantaneous Bandwidth
East China Normal University（华东师范大学）；Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences（中国科学院上海光学精密机械研究所）；University of Chinese Academy of Sciences（中国科学院大学）
Achieving 100$\,$MHz Instantaneous Bandwidth in a Broadband Rydberg Microwave Sensor
Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences（中国科学院上海光学精密机械研究所）；East China Normal University（华东师范大学）；University of Chinese Academy of Sciences（中国科学院大学）
The sensitivity of quantum magnetometers is challenged by control errors and, especially in the solid-state, by their short coherence times. Refocusing techniques can overcome these limitations and improve the sensitivity to periodic fields, but they come at the cost of reduced bandwidth and cannot be applied to sense static (DC) or aperiodic fields. Here we experimentally demonstrate that continuous driving of the sensor spin by a composite pulse known as rotary-echo (RE) yields a flexible magnetometry scheme, mitigating both driving power imperfections and decoherence. A suitable choice of R…
We report on our progress in the development of an atomic magnetometer (AM) based low-frequency magnetic particle imaging (MPI) scanner, expected to be free from Specific Absorption Rate (SAR) and Peripheral Nerve Stimulation (PNS) constraints. We address major challenges in coil and sensor design due to specific AM properties. Compared to our previous work we have changed the AM's mode of operation towards its implementation for detecting weak magnetic nanoparticles (MNP) response fields in the presence of nearby-located strong drive/selection fields. We demonstrate that a pump-probe AM schem…
We study the bandwidth and multiplexing capacity of an erbium-doped optical memory for quantum storage purposes. We concentrate on the protocol ROSE (Revival of a Silenced Echo) because it has the largest potential multiplexing capacity. Our analysis is applicable to other protocols that involve strong optical excitation. We show that the memory performance is limited by instantaneous spectral diffusion and we describe how this effect can be minimised to achieve optimal performance.
We demonstrate a new method for measuring radio frequency (RF) electric fields based on quantum interference in an atom. Using a bright resonance prepared within an electromagnetically induced transparency window we are able to achieve a sensitivity of ~ 30 μV cm^-1 sqrt(Hz)^-1. For this work, we demonstrated detection of RF electric fields as small as ~ 8 μV cm^-1. The sensitivity is currently limited by the spectral bandwidth of the lasers used in the experiment and can be significantly improved in the future. The method can serve as a new quantum based standard for RF electrometry. The repr…
Atomic magnetometry was performed at Earth's magnetic field over a free-space distance of ten meters. Two laser beams aimed at a distant alkali-vapor cell excited and detected the $^{87}$Rb magnetic resonance, allowing the magnetic field within the cell to be interrogated remotely. Operated as a driven oscillator, the magnetometer measured the geomagnetic field with \lessgtrsim{\lesssim}3.5\,pT precision in a $\sim$2\,s data acquisition; this precision was likely limited by ambient field fluctuations. The sensor was also operated in self-oscillating mode with a 5.3\,pT/$\sqrt{\textrm{Hz}}$ noi…
We report on a two-channel magnetometer based on nonlinear magneto-optical rotation in a Cs glass cell with buffer gas. The Cs atoms are optically pumped and probed by free running diode lasers tuned to the D$_2$ line. A wide frequency modulation of the pump laser is used to produce both synchronous Zeeman optical pumping and hyperfine repumping. The magnetometer works in an unshielded environment and spurious signal from distant magnetic sources is rejected by means of differential measurement. In this regime the magnetometer simultaneously gives the magnetic field modulus and the field diffe…
Compressive Spectrum Sensing via Spectral Multiplexing in Rydberg Atomic Receiver
School of physics, Harbin Institute of Technology（哈尔滨工业大学物理学院）；Key Laboratory of Quantum Information, University of Science and Technology of China（中国科学技术大学量子信息重点实验室）
Phase projection errors in rf-driven optically pumped magnetometers
Institute of Physics Belgrade, University of Belgrade（贝尔格莱德物理研究所，贝尔格莱德大学）；Physics Department, University of Fribourg（弗里堡大学物理系）；Leibniz Institute of Photonic Technology（莱布尼茨光子技术研究所）
