3D sub-attonewton force sensing with a single atom

Erik W. Streed, Valdis Blūms, Marcin Piotrowski +5 more

Benjamin Safvati, Yi‐Ting Chen, Morgan Brubaker +1 more

Valdis Blūms, Marcin Piotrowski, Mahmood Irtiza Hussain +5 more

Forces drive all physical interactions. High-sensitivity measurement of the effect of forces enables the quantitative investigation of physical phenomena. Laser-cooled trapped atomic ions are a well-controlled quantum system whose low mass, strong Coulomb interaction, and readily detectable fluorescence signal make them a favorable platform for precision metrology. We demonstrate a three-dimensional sub-attonewton sensitivity force sensor based on a super-resolution imaging of a single trapped ion. The force is detected by measuring the ion's displacement in three dimensions with nanometer precision. Observed sensitivities were 372 ± 9, 347 ± 18, and 808 ± 51 zN/[Formula: see text], corresponding to 24×, 87×, and 21× above the quantum limit. We verified this technique by measuring a 95-zN light pressure force, an important systematic effect in optically based sensors.

Yang Liu, Pengfei Lu, Xinxin Rao +6 more

Mechano-optical transducers are devices that convert a force or displacement signal to an optical one, enabling ultrasensitive mechanical detection. Currently, ultraweak DC force sensors with high spatial resolution are in high demand for the search of possible exotic spin-dependent interactions beyond the standard model in sub-millimeter scale. Here, we demonstrate a mechano-optical transducer of a single trapped ion with the force sensitivity about 600 zN/Hz for the DC force. This method utilizes the Doppler shift of the time-resolved fluorescence to detect the ion's micromotion that is coupled to a vector force. By alternating the directions of the detection laser beams, the vector DC forces can be precisely measured. Such a mechano-optical transducer provides sub-attonewton sensitivity with the spatial resolution in single-atom level, enabling various uses for both scientific and industrial purposes.

Franck Pereira dos Santos, Yann Balland, Luc Absil

Juste Deuyekbe, Philippe Djorwé, A. -H. Abdel-Aty +3 more

In single-port non-Hermitian sensors the Petermann factor offsets susceptibility gains, imposing a strict resource bound on metrological precision. We test whether a multi-port geometry can evade this bound: a double-chain optomechanical ladder with opposing non-reciprocal hoppings spatially separates signal amplification from quantum-noise drainage, and gradient-based differentiable optimal control (DOC) maximizes the resource-normalized Fisher information $\Fnorm$ subject to a Hurwitz-stability constraint. Across system sizes $N\in\{\num{6},\dots,\num{16}\}$ the optimizer returns $\Fnorm>0$ in every case, with two coexisting solution classes whose selection is initialization-dependent: deep-stability configurations achieve $\Fnorm\in\numrange{0.937}{0.987}$ with attenuated transmission, while marginal-stability configurations deliver directional gain $\Gfwd\in\qtyrange{13.5}{15.5}{\dB}$ with isolation $\Iso\in\qtyrange{40}{64}{\dB}$. A multi-restart ensemble reveals these classes are the endpoints of a precision--gain frontier. All solutions remain Hurwitz-stable under \qty{5}{\percent} disorder (\qty{87.5}{\percent} recovery), and the deep-stability advantage survives realistic preamplifier noise at $\Fnormeff\approx\num{0.3}$--$\num{0.5}$. Mapped onto circuit-QED parameters, the architecture enables sub-attonewton force sensing and broadband axion searches across the \qtyrange{1}{10}{\giga\hertz} band.