The shot-noise detection limit in current high-precision atomic magnetometry is a manifestation of quantum fluctuations that scale as the square root of N in an ensemble of N particles. However, there is a general expectation that the reduced projection noise provided by conditional spin-squeezing could be exploited to surpass the conventional shot-noise limit. We show that continuous measurement coupled with quantum Kalman filtering provides an optimal procedure for magnetic detection limits that scale with 1/N, the Heisenberg squeezing limit. Our analysis demonstrates the importance of optimal estimation procedures for high bandwidth precision magnetometry.
@article{arxiv.quant-ph/0306192,
title = {Quantum Kalman Filtering and the Heisenberg Limit in Atomic Magnetometry},
author = {JM Geremia and John K. Stockton and Andrew C. Doherty and Hideo Mabuchi},
journal= {arXiv preprint arXiv:quant-ph/0306192},
year = {2007}
}
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