Abstract
Recently, several reports with a strong focus on compact, nonstationary optical atomic clocks have been published, including accounts of in-field deployment of these devices for demonstrations of chronometric levelling in different types of environments. We review recent progress in this research area, comprising compact and transportable neutral atom and single-ion optical atomic clocks. The identified transportable optical clocks strive for low volume, weight and power consumption while exceeding standard microwave atomic clocks in fractional frequency instability and systematic uncertainty. Some transportable clock projects additionally address requirements for metrology or serve the joint technology development between industrial and academic stakeholders. Based on the reviewed reports on nonstationary optical atomic clocks, we suggest definitions for transportable, portable and mobile optical atomic clocks. We conclude our article with an overview of possible future directions for developments of optical clock technology.
Funding source: UK Quantum Technology Hub Sensors and Timing
Award Identifier / Grant number: EP/T001046/1
Funding source: European Union
Award Identifier / Grant number: 820404
About the authors
Dr. Markus Gellesch is an experimental physicist. Currently, he is working on transportable lattice clocks as part of the EU quantum flagship project iqClock. Markus also has a strong interest in outreach work and has recently collaborated with a local artist to realise a comic booklet on the theme of optical atomic clocks. (https://quantumclocks.the-comic.org/)
Dr. Jonathan Jones is an early stage researcher with a focus on developing cold atoms and optical clock technology for application in the real world. He has published work on ion trapping, optical clocks, quantum metrology and time variation of fundamental constants. Currently he is leading the group’s work on optical cavities in addition to working on transportable lattice clocks as part of the EU quantum flagship programme “iqClock”.
Richard Barron joined the group during his master’s project in 2016 and has carried on through to a PhD, working mostly on the production of atoms to load into a MOT. Currently on the iqClock project.
Dr. Alok Singh is an experimental Optical and Atomic Physicist and he works at precision hyperfine frequency measurements, coherent population trapping/oscillation, Bose-Fermi mixture, dipole-dipole/quadrupole Forster resonance transitions in Rydberg atoms and cold atoms for atomic clock. He has published on the impact of cold atoms, precision frequency measurements and coherent population trapping/oscillation. His recent research focuses on atomic optical lattice clock using Sr atoms with Miniature Optical Lattice Clock project and iqClock-Integrated Quantum Clock project.
Dr. Qiushuo Sun is a knowledge exchange fellow at the Centre for Innovation in Advanced Measurement in Manufacturing (CIAMM) at the University of Birmingham. She joined the group in September 2019 and has been working on the high-finesse optical cavities and the lasers for the optical clocks. She also helps support local SMEs in Research and Development in state–of–the–art optical technologies and instruments.
Professor Kai Bongs is a Principle Investigator at the UK Quantum Technology Hub Sensors and Timing, where he helps to drive the translation of gravity sensors and ultraprecise clocks into technology and applications across a diverse number of different sectors. Professor Bongs is also College Director of Innovation at the University of Birmingham. He is a Royal Society Wolfson Research Merit Fellow, as well as a Fellow of the Institute of Physics and the Institution of Engineering and Technology.
Dr. Yeshpal Singh is a senior lecturer at the University of Birmingham and leads the cold atoms based Sr group. His main research interests are translation of quantum concepts to quantum technology, quantum metrology and precision measurements, Bose–Einstein condensates in microgravity, ultracold Bosons, degenerate Fermi gases and quantum phase transitions, and ultracold molecules and quantum state engineering.
Acknowledgements
The authors are grateful for receiving funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 820404 (iqClock project) and acknowledge the fruitful joint work with partners from the iqClock Consortium. We further recognise sponsorship from the UK Quantum Technology Hub Sensors and Timing (grant EP/T001046/1).
Author contribution: MG and YS wrote the manuscript with contributions from JJ, AS, QS, RB, and KB. All authors are involved with the iqClock project for realising a transportable optical lattice clock demonstrator. All authors have reviewed and approved the manuscript.
Research funding: The authors are grateful for receiving funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 820404 (iqClock project) and acknowledge the fruitful joint work with partners from the iqClock Consortium. We further recognise sponsorship from the Quantum Hub for Sensors and Metrology (EPSRC funding within grant EP/M013294/1).
Conflict of interest statement: The authors declare no conflicts of interest regarding this article.
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