The precision of a quantum sensor can overcome its classical counterpart when its constituents are entangled. In gaussian squeezed states, quantum correlations lead to a reduction of the quantum projection noise below the shot noise limit. However, the most sensitive states involve complex non-gaussian quantum fluctuations, making the required measurement protocol challenging. Here we measure the sensitivity of non-classical states of the electronic spin J=8 of dysprosium atoms, created using light-induced non-linear spin coupling. Magnetic sublevel resolution enables us to reach the optimal sensitivity of non-gaussian (oversqueezed) states, well above the capability of squeezed states and about half the Heisenberg limit.
@article{arxiv.1901.06282,
title = {Enhanced magnetic sensitivity with non-gaussian quantum fluctuations},
author = {Alexandre Evrard and Vasiliy Makhalov and Thomas Chalopin and Leonid A. Sidorenkov and Jean Dalibard and Raphael Lopes and Sylvain Nascimbene},
journal= {arXiv preprint arXiv:1901.06282},
year = {2019}
}