@article{13289,
  author = {Johannes Franke and Sean Muleady and Raphael Kaubruegger and Florian Kranzl and Rainer Blatt and Ana Maria Rey and Manoj Joshi and Christian Roos},
  title = {Quantum-enhanced sensing on optical transitions through finite-range interactions},
  abstract = {<p>The control over quantum states in atomic systems has led to the most precise optical atomic clocks so far. Their sensitivity is bounded at present by the standard quantum limit, a fundamental floor set by quantum mechanics for uncorrelated particles, which can—nevertheless—be overcome when operated with entangled particles. Yet demonstrating a quantum advantage in real-world sensors is extremely challenging. Here we illustrate a pathway for harnessing large-scale entanglement in an optical transition using 1D chains of up to 51 ions with interactions that decay as a power-law function of the ion separation. We show that our sensor can emulate many features of the one-axis-twisting (OAT) model, an iconic, fully connected model known to generate scalable squeezing4 and Greenberger–Horne–Zeilinger-like states5,6,7,8. The collective nature of the state manifests itself in the preservation of the total transverse magnetization, the reduced growth of the structure factor, that is, spin-wave excitations (SWE), at finite momenta, the generation of spin squeezing comparable with OAT (a Wineland parameter9,10 of −3.9 ± 0.3 dB for only N = 12 ions) and the development of non-Gaussian states in the form of multi-headed cat states in the Q-distribution. We demonstrate the metrological utility of the states in a Ramsey-type interferometer, in which we reduce the measurement uncertainty by −3.2 ± 0.5 dB below the standard quantum limit for N = 51 ions.</p>
},
  year = {2023},
  journal = {Nature},
  volume = {621},
  pages = {740},
  month = {2023-08},
  publisher = {Springer Science and Business Media LLC},
  doi = {10.1038/s41586-023-06472-z},
}