Improved absolute clock stability by the joint interrogation of two atomic ensembles
Authors: Li W., Wu S.; Smerzi A., Pezzè L.
Autors Affiliation: Shenzhen Key Laboratory of Ultraintense Laser and Advanced Material Technology, Center for Advanced Material Diagnostic Technology, College of Engineering Physics, Shenzhen Technology University, Shenzhen, 518118, China; Guangdong Provincial Key Laoratory of Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China; QSTAR, INO-CNR, LENS, Largo Enrico Fermi 2, Firenze, 50125, Italy; Institute of Theoretical Physics, Department of Physics, Shanxi University, Taiyuan, 030006, China
Abstract: Improving the clock stability is of fundamental importance for the development of quantum-enhanced metrology. One of the main limitations arises from the randomly fluctuating local oscillator (LO) frequency, which introduces “phase slips” for long interrogation times and hence the failure of the frequency-feedback loop. Here we propose a strategy to improve the stability of atomic clocks by interrogating two atomic ensembles sharing the same LO. The two ensembles are prepared in coherent spin states pointing along orthogonal directions in the Bloch sphere. While standard Ramsey interrogation can only determine phases unambiguously in the interval [-p/2,p/2], the joint interrogation allows for an extension to [-p,p], resulting in a relaxed restriction of the Ramsey time and improvement of absolute clock stability. Theoretical predictions are supported by ab initio numerical simulation for white and correlated LO noise. While our basic protocol uses uncorrelated atoms, we further extended it to include spin-squeezing and further improving the scaling of clock stability with the number of atoms. Our protocol can be readily tested in current state-of-the-art experiments.
Journal/Review: PHYSICAL REVIEW A
Volume: 105 (5) Pages from: 053116-1 to: 053116-15
More Information: We thank A. Bertolldi, K. Hammerer, F. Levi, M. Schulte, and M. Tarallo for discussions. We acknowledge funding of the project EMPIR-USOQS, EMPIR projects are cofunded by the European Unions Horizon2020 research and innovation program and the EMPIR Participating States. We also acknowledge support by the H2020 QuantERA ERA-NET co-fund QCLOCKS. This research was supported by the National Key R&D Program of China (Grant No. 2017YFA0304500) , National Natural Science Foundation of China (Grant No. 11874247) , 111 project (Grant No. D18001) , the Hundred Talent Program of the Shanxi Province (2018).KeyWords: quantum projection noise; statesDOI: 10.1103/PhysRevA.105.053116