Dynamical decoupling of laser phase noise in compound atomic clocks

authored by: Sören Dörscher, Ali Al-Masoudi, Marcin Bober, Roman Schwarz, Richard Hobson, Uwe Sterr, Christian Lisdat
Abstract: The frequency stability of many optical atomic clocks is limited by the coherence of their local oscillator. Here, we present a measurement protocol that overcomes the laser coherence limit. It relies on engineered dynamical decoupling of laser phase noise and near-synchronous interrogation of two clocks. One clock coarsely tracks the laser phase using dynamical decoupling; the other refines this estimate using a high-resolution phase measurement. While the former needs to have a high signal-to-noise ratio, the latter clock may operate with any number of particles. The protocol effectively enables minute-long Ramsey interrogation for coherence times of few seconds as provided by the current best ultrastable laser systems. We demonstrate implementation of the protocol in a realistic proof-of-principle experiment, where we interrogate for 0.5 s at a laser coherence time of 77 ms. Here, a single lattice clock is used to emulate synchronous interrogation of two separate clocks in the presence of artificial laser frequency noise. We discuss the frequency instability of a single-ion clock that would result from using the protocol for stabilisation, under these conditions and for minute-long interrogation, and find expected instabilities of σ_y(τ) = 8 × 10⁻¹⁶(τ/s)^−1/2 and σ_y(τ) = 5 × 10⁻¹⁷(τ/s)^−1/2, respectively.
External Organisation(s): National Metrology Institute of Germany (PTB)
IAV GmbH
Nicolaus Copernicus University
National Physical Laboratory (NPL)
Type: Article
Journal: Communications Physics
Volume: 3
Publication date: 01.12.2020
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Physics and Astronomy(all)
Electronic version(s): https://doi.org/10.1038/s42005-020-00452-9 (Access: Open)

BibTeX

@article{e46db0043f9d4b9cb566c03396442dae,
title = "Dynamical decoupling of laser phase noise in compound atomic clocks",
abstract = "The frequency stability of many optical atomic clocks is limited by the coherence of their local oscillator. Here, we present a measurement protocol that overcomes the laser coherence limit. It relies on engineered dynamical decoupling of laser phase noise and near-synchronous interrogation of two clocks. One clock coarsely tracks the laser phase using dynamical decoupling; the other refines this estimate using a high-resolution phase measurement. While the former needs to have a high signal-to-noise ratio, the latter clock may operate with any number of particles. The protocol effectively enables minute-long Ramsey interrogation for coherence times of few seconds as provided by the current best ultrastable laser systems. We demonstrate implementation of the protocol in a realistic proof-of-principle experiment, where we interrogate for 0.5 s at a laser coherence time of 77 ms. Here, a single lattice clock is used to emulate synchronous interrogation of two separate clocks in the presence of artificial laser frequency noise. We discuss the frequency instability of a single-ion clock that would result from using the protocol for stabilisation, under these conditions and for minute-long interrogation, and find expected instabilities of σy(τ) = 8 × 10−16(τ/s)−1/2 and σy(τ) = 5 × 10−17(τ/s)−1/2, respectively.",
author = "S{\"o}ren D{\"o}rscher and Ali Al-Masoudi and Marcin Bober and Roman Schwarz and Richard Hobson and Uwe Sterr and Christian Lisdat",
note = "Funding information: We thank S. H{\"a}fner, Th. Legero, and E. Benkler for operating the ultrastable laser system and optical frequency comb that are used for stabilisation of our interrogation laser system. We thank M. Misera for developing the frequency noise generator. This work has received funding from Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) within CRC 1227 ({\textquoteleft}DQ-mat{\textquoteright}, project B02) and under Germany{\textquoteright}s Excellence Strategy—EXC-2123 QuantumFrontiers—390837967. This work was partially supported by the Max Planck–RIKEN–PTB Center for Time, Constants and Fundamental Symmetries. R.H. has been supported by the European Union{\textquoteright}s Horizon H2020 MSCA RISE programme under Grant Agreement Number 691156 (Q-SENSE). M.B. has been supported by a research fellowship within the project {\textquoteleft}Enhancing Educational Potential of Nicolaus Copernicus University in the Disciplines of Mathematical and Natural Sciences{\textquoteright} (Project No. POKL.04.01.01-00-081/10). U.S. acknowledges funding from the project EMPIR 17FUN03 USOQS. EMPIR projects are co-funded by the European Union{\textquoteright}s Horizon 2020 research and innovation programme and the EMPIR Participating States.",
year = "2020",
month = dec,
day = "1",
doi = "10.1038/s42005-020-00452-9",
language = "English",
volume = "3",
journal = "Communications Physics",
publisher = "Springer Nature",
number = "1",
}