Femtotesla nearly quantum-noise-limited pulsed gradiometer at Earth-scale fields

Abstract

We describe a finite fields magnetic gradiometer using an intense pulsed laser to polarize a ${}^{87}$Rb atomic ensemble and a compact VCSEL probe laser to detect paramagnetic Faraday rotation in a single multipass cell. We report differential magnetic sensitivity of $14$ fT/Hz${}^{1/2}$ over a broad dynamic range including Earth's field magnitude and common-mode rejection ratio higher than $10^4$. We also observe a nearly quantum-noise-limited behaviour of the gradiometer, by comparing the experimental standard deviation of the estimated frequency difference against the Cramér-Rao lower bound in the presence of white photon shot-noise, atomic spin noise and atomic diffusion.

arXiv comment4 pages, 4 figures

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Cited by in corpus (6)

• Heading-error-free optical atomic magnetometry in the Earth-field range
• Quantum-enhanced magnetometry at optimal number density
• Pulsed Vector Atomic Magnetometer Using an Alternating Fast-Rotating Field
• Optical pumping enhancement of a free-induction-decay magnetometer
• Inter-species spin-noise correlations in hot atomic vapors
• Free-induction-decay magnetic field imaging with a microfabricated Cs vapor cell