Spin-squeezed clock precision beyond the standard quantum limit at the 10<sup>-18</sup> level
ORAL
Abstract
Optical atomic clocks, with unrivaled precision and accuracy, have advanced the frontier of precision measurement science and opened new avenues for exploring fundamental physics [1–3]. A fundamental limitation to clock precision is the Standard Quantum Limit (SQL), set by uncorrelated projection noise. State-of-the-art optical lattice clocks mitigate the SQL by interrogating large ensembles, but density-dependent frequency shifts hinder further scaling of the atom number. Entanglement offers a route beyond SQL, yet achieving a clear quantum advantage at state-of-the-art stability has remained challenging.
In this talk, I will present a spin-squeezed optical lattice clock operating beyond the SQL, achieving a fractional frequency precision of 1.1 ×10−18 for a single spin-squeezed clock [4]. Using cavity-based quantum nondemolition (QND) measurements, we prepare two spin-squeezed ensembles of ∼30,000 strontium atoms confined in a two-dimensional optical lattice. A synchronous clock comparison with an interrogation time of 61 ms achieves a metrological improvement of 2.0(2) dB beyond the SQL, after correcting for state preparation and measurement errors. These results establish the most precise entanglement-enhanced clock to date, provide a foundation for accuracy evaluations of spin-squeezed clocks, and offer a powerful platform for exploring the interplay of gravity and quantum entanglement. I will conclude with recent progress toward longer interrogation times and reduced technical noise, and discuss an outlook toward entanglement-assisted precision approaching the 10-20 regime.
References:
[1] A. D. Ludlow et al., Rev. Mod. Phys. 87, 637 (2015).
[2] T. Bothwell et al., Nature 602, 420 (2022).
[3] A. Aeppli et al., Phys. Rev. Lett. 133, 023401 (2024).
[4] Y. A. Yang et al., Phys. Rev. Lett. 135, 193202 (2025).
In this talk, I will present a spin-squeezed optical lattice clock operating beyond the SQL, achieving a fractional frequency precision of 1.1 ×10−18 for a single spin-squeezed clock [4]. Using cavity-based quantum nondemolition (QND) measurements, we prepare two spin-squeezed ensembles of ∼30,000 strontium atoms confined in a two-dimensional optical lattice. A synchronous clock comparison with an interrogation time of 61 ms achieves a metrological improvement of 2.0(2) dB beyond the SQL, after correcting for state preparation and measurement errors. These results establish the most precise entanglement-enhanced clock to date, provide a foundation for accuracy evaluations of spin-squeezed clocks, and offer a powerful platform for exploring the interplay of gravity and quantum entanglement. I will conclude with recent progress toward longer interrogation times and reduced technical noise, and discuss an outlook toward entanglement-assisted precision approaching the 10-20 regime.
References:
[1] A. D. Ludlow et al., Rev. Mod. Phys. 87, 637 (2015).
[2] T. Bothwell et al., Nature 602, 420 (2022).
[3] A. Aeppli et al., Phys. Rev. Lett. 133, 023401 (2024).
[4] Y. A. Yang et al., Phys. Rev. Lett. 135, 193202 (2025).
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Publication: Y. A. Yang et al., Phys. Rev. Lett. 135, 193202 (2025)
Presenters
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Yang Yang
- JILA, University of Colorado Boulder