Speaker
Description
Over the past 20 years optical frequency combs [1], with atomic clocks [2], have been a powerful and enabling technology in the context of time and frequency measurement [1,2]. Impressively, optical atomic clocks have yielded an 8 order of magnitude improvement in accuracy in the past 30 years. These improvements are fueling a push toward redefinition of the SI second to optical atomic references [3], as well as application of atomic clocks to tests of fundamental physics [4] and as relativistic gravitational sensors [5-6]. Unfortunately, the long measurement times needed to average down clock quantum projection noise and local oscillator noise to reach measurement stabilities at and beyond the 10-18 level, limit the feasibility of next-generation applications.
I will present the improved instability results for an inter-species optical atomic clock comparison us-ing a differential measurement technique, Figure 1. In this technique, the single ion 27Al+ clock near and the 171Yb lattice clock shared a common local oscillator using the phase coherent wavelength con-version with an optical frequency comb. This technique enabled nearly a factor of 10 improvement in 1-s measurement resolution and a 100-time improvement in averaging time to reach a measurement instability of 10-18. Improvements in the measurement stability was achieved via a minimization of laser noise aliasing, and via improvement in the 27Al+ clock quantum projection noise by increasing its probe time by mitigating laser-atomic decoherence [7].
References
[1] Fortier, T.M. and Baumann, E., “20 years of developments in optical frequency comb technology and applica-tions,” Communications Physics 2, Article number 153 (2019).
[2] Ludlow, A. D., Boyd, M. M., Ye, J., Peik, E. & Schmidt, P. O., “Optical atomic clocks,” Rev. Mod. Phys. 87, 637–701 (2015).
[3] Riehle, F., Gill, P., Arias, F. & Robertsson, L. “The CIPM list of recommended frequency standard values: guidelines and procedures. Metrologia,” 55, 188–200 (2018).
[4] BACON collaboration: “Frequency ratio measurements at 18-digit accuracy using an optical clock network,” Na-ture 591 (2021).
[5] Rosenband, T. et al. “Frequency ratio of Al+ and Hg+ single-ion optical clocks; metrology at the 17th decimal place,” Science 319, 1808–1812 (2008).
[6] Mehlstäubler, T. E., Grosche, G., Lisdat, C., Schmidt, P. O. & Denker, H. Atomic clocks for geodesy. Rep. Prog. Phys. 81, 064401 (2018).
[7] Kim, M et al., “Improved interspecies optical clock comparisons through differential spectroscopy,” Nat. Phys. 19 (2023)
