Quantum-amplified global-phase spectroscopy on an optical clock transition

We are delighted to welcome Dr Leon Zaporski from MIT to the Cavendish Laboratory on Monday 1 December 2025 who will deliver the talk on ‘Quantum-amplified global-phase spectroscopy on an optical clock transition’. 

Abstract: Optical lattice clocks (OLCs) are at the forefront of precision metrology, operating near a standard quantum limit (SQL) set by quantum noise. Harnessing quantum entanglement offers a promising route to surpass this limit, yet there remain practical roadblocks concerning scalability and measurement resolution requirements. In this talk I will introduce a recently discovered Rabi-type “global-phase spectroscopy” (GPS) that utilizes the detuning-sensitive global Aharanov-Anandan phase and borrows from the holonomic-quantum-gate concept. Marrying the GPS with cavity-feedback spin squeezing we were able to demonstrate quantum-amplified time-reversal spectroscopy on an optical clock transition which achieved directly measured 2.4(7) dB metrological gain, and 4.0(8) dB improvement in laser noise sensitivity beyond the SQL. To this end, we introduced rotary echo to protect the dynamics from inhomogeneities in light-atom coupling and implemented a laser-noise-canceling differential measurement through symmetric phase encoding in two nuclear spin states. Our technique is not limited by measurement resolution, scales easily owing to the global nature of entangling interaction, and exhibits high resilience to typical experimental imperfections. We expect it to be broadly applicable to next-generation atomic clocks and other quantum sensors approaching the fundamental quantum precision limits.

Learn more about the research in the Nature article: https://www.nature.com/articles/s41586-025-09578-8 or in the MIT News feature: MIT News: Physicists improve atomic clocks’ precision

Be sure to save the date for this insightful session with Dr Zaporski. More details on the exact time of the seminar and the venue will follow soon.