Wisconsin Quantum Institute |
Events on Friday, September 19th, 2025
- Spin-Squeezed Atomic Clock with Precision Beyond the Standard Quantum Limit at the 10⁻¹⁸ Level
- Time: 10:00 am - 11:00 am
- Place: 5280 Chamberlin
- Speaker: Joonseok Hur, University of Colorado Boulder
- Abstract: Optical atomic clocks (OACs), utilizing optical transitions in atoms as a timebase, have achieved unprecedented precision and accuracy in scientific measurement, offering new frontiers in metrology and fundamental physics.
The precision of state-of-the-art OACs has reached the standard quantum limit (SQL), the fundamental bound set by quantum projection noise in measurements on uncorrelated atoms. While increasing atom numbers can statistically suppress this noise, it also introduces unwanted atomic interactions that compromise clock accuracy. Engineered entanglement between atoms can overcome the SQL, and atomic clocks with spin-squeezed states have demonstrated improved precision with various platforms. However, quantum advantage in entanglement-enhanced clocks, surpassing the best precision of conventional OACs, has yet to be achieved.
In this talk, I will present our spin-squeezed optical lattice clock that achieves precision beyond the SQL at the 10⁻¹⁸ level, representing a significant step toward quantum advantage in optical clocks. We squeezed the collective projection noise of 30,000 atoms by 7.1(1.0) dB using quantum nondemolition measurements mediated by strong atom-cavity coupling. Improved motional control preserves clock-state coherence, resulting in a 5.1(1.0) dB metrological enhancement. A synchronous comparison between two independent spin-squeezed clock ensembles demonstrates a 2.0(2) dB improvement beyond the SQL, reaching a fractional instability of 1.1×10⁻¹⁸.
This work marks a milestone toward quantum-enhanced timekeeping and provides a promising platform to explore the interplay between gravity and quantum entanglement. - Host: Josiah Sinclair