Preparation of squeezed spin states of atoms for subquantum interferometry

Christan Groß

Mark A. Kasevich, Benjamin K. Malia

Mark A. Kasevich

Nils J. Engelsen, Onur Hosten, Rajiv Krishnakumar +1 more

We create up to 20 dB spin-squeezed states of atomic ensembles using an optical cavity-based measurement. The prepared states are suitable for atomic sensors that require free space release of the atoms.

Baochen Wu, Graham P. Greve, James K. Thompson

Joshua Goldsmith, J. J. Hope, Simon A. Haine

We develop a framework for describing the effects of systematic state-preparation error in quantum-enhanced atom interferometry on sensing performance. We do this in the context of both spin-squeezed and non-Gaussian states for the two-axis-twisting (TAT), one-axis-twisting (OAT), and twist-and-turn (TNT) state-preparation schemes, and derive general conditions for robustness and susceptibility of quantum states to state-preparation error. In the spin-squeezing regime, we find that OAT is more susceptible to state-preparation error than TAT due to its parameter-dependent phase-space rotation. In the non-Gaussian regime, we find that OAT is robust to state-preparation errors, which can be explained by a small ratio of off-diagonal to diagonal elements in its Fisher-covariance matrix. In contrast, TNT does not exhibit this robustness. We find that the single-parameter unbiased estimators that are habitually used in quantum-enhanced atom interferometry are not always optimal, and that there may be occasions where biased estimators, or two-parameter unbiased estimators, lead to lower net error.