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Measurement Sensors

Opticlock: Transportable and easy-to-operate optical single-ion clock

J. Stühler, Moustafa Abdel Hafiz, Bassem Arar, Ahmad Bawamia, K. Bergner, Maximilian Biethahn, Stefan Brakhane, Alexandre Didier, József Fortágh, Matthäus Halder, Ronald Holzwarth, Nils Huntemann, M. Johanning, Robert Jördens, Wilhelm G. Kaenders, Florian Karlewski, Florian Kienle, Markus Krutzik, Maurice Lessing, T. E. Mehlstäubler, Dieter Meschede, E. Peik, Achim Peters, Piet O. Schmidt, Hendrik Siebeneich, Chr. Tamm, Enrico Vogt, Andreas Wicht, C. Wunderlich, Jialiang Yu

Published Oct 6, 2021• 38 citations

Abstract

We report on a transportable and easy-to-operate optical clock utilizing the 2S1/2 - 2D3/2 transition of a single trapped 171Yb+ ion at 436 nm. Developed within a pilot project for quantum technology in Germany lead by industry, the clock is set up in two 19″ racks. In this way, transportation can easily be realized, and the large degree of automatization allows for operation outside highly specialized laboratories for applications beyond basic research. Comparisons to existing high-accuracy optical clock systems enable a verification of the clock's stability and uncertainty budget at the low 10−17 level. During these tests, operation with 99.8% availability over more than 14 days has been achieved.

DOI: 10.1016/j.measen.2021.100264

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We report on a transportable and easy-to-operate optical clock utilizing the 2S1/2 - 2D3/2 transition of a single trapped 171Yb+ ion at 436 nm. Developed within a pilot project for quantum technology in Germany lead by industry, the clock is set up in two 19″ racks. In this way, transportation can easily be realized, and the large degree of automatization allows for operation outside highly specialized laboratories for applications beyond basic research. Comparisons to existing high-accuracy optical clock systems enable a verification of the clock's stability and uncertainty budget at the low 10−17 level. During these tests, operation with 99.8% availability over more than 14 days has been achieved.

We present the setup of our optical frequency standard (OFS) “TOPTICLOCK”. It is based on the 2S1/2 (F=0) – 2D3/2 (F=2) electric quadrupole transition at 435.5 nm of a single laser-cooled and trapped 171Yb+ ion. All required subsystems are contained in two transportable 19” rack compartments. By comparing it with a laboratory-style OFS of the German National Metrology Institute (PTB), which operates on the 467 nm electric octupole transition, using a TOPTICA DFC optical frequency comb, a frequency instability of 5×10-15/√τ with systematic uncertainty below 2×10-17 was demonstrated. The performance of TOPTICLOCK was also benchmarked by directly comparing it to another OFS operating also at the 435.5 nm clock transition. An agreement between both systems with a total uncertainty well below 10-17 was obtained.

For the past 15 years, tremendous progress within the fields of laser stabilization, optical frequency combs and atom cooling and trapping have allowed the realization of optical atomic clocks with unrivaled performances. These instruments can perform frequency comparisons with fractional uncertainties well below 10-17, finding applications in fundamental physics tests, relativistic geodesy and time and frequency metrology. Even though most optical clocks are currently laboratory setups, several proposals for using these clocks for field measurements or within an optical clock network have been published, and most of time and frequency metrology institutes have started to develop transportable optical clocks. For the purpose of this special issue, we chose to focus on trapped-ion optical clocks. Even though their short-term fractional frequency stability is impaired by a lower signal-to-noise ratio, they offer a high potential for compactness: trapped ions demand low optical powers and simple loading schemes, and can be trapped in small vacuum chambers. We review recent advances on the clock key components, including ion trap and ultra-stable optical cavity, as well as existing projects and experiments which draw the picture of what future transportable, single-ion optical clocks may resemble.

SummaryThe optical clock based on trapped ions has attracted great interest due to the important significance in fundamental physics and application prospects in metrology of time and frequency. The ytterbium ion has unique advantages in developing transportable and miniaturized optical clocks because it has long storage time and its related laser system is compact. In addition, the171Yb+ion has two clock transition lines, which can perform frequency self-comparison. This paper mainly introduces the progress in the development of the transportable optical clock system based on the single171Yb+ion at Tsinghua University, China. A transportable physical package, including the vacuum system, optic system and imaging system is presented and implemented to automatically detect the presence of trapped ion.