Editorial Feature

What are Optical Lattice Clocks?

The optical lattice clock has revolutionized scientific timekeeping by achieving unprecedented levels of accuracy. This article will introduce an overview of optical lattice clocks, how they work, their impact on precision timekeeping, and recent research findings.

optical lattice clocks, What are Optical Lattice Clocks

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Optical lattice clocks are next-generation atomic clocks that use ultracold neutral (strontium and ytterbium) atoms confined in a 3D optical lattice to create a highly precise time measurement.

This revolutionary technology was first proposed in 2001 by KATORI Hidetoshi and is now widely recognized internationally as a secondary representation of the System International (SI) second.

These clocks offer 18-digit precision in time measurement, corresponding to an error of only one second in 30 billion years.

How Do Optical Lattice Clocks Work?

Optical lattice clocks use a lattice of bright and dark spots created by light wave interference to trap single atoms, which are cooled to near absolute zero to minimize motion.

The atoms are held using light that shifts their energy levels, but a "magic wavelength" ensures that the clock frequency remains unchanged. The clock measures time by determining the frequency of the transition between the atom's energy levels, and the use of several thousand atoms improves accuracy through averaging measurements.

Improving Precision Timekeeping with Optical Lattice Clocks

The current definition of time (second) relies on cesium atomic clocks that work by measuring the oscillation of light waves. Although cesium atomic clocks are highly efficient, there is room for improvement as Doppler shifts and measurement processes introduce some uncertainty.

Optical lattice clocks offer a promising solution as they have very high governing frequencies, which results in higher stability and lower frequency uncertainties. In addition, these clocks can use thousands of neutral atoms simultaneously, leading to very low instabilities and excellent signal-to-noise ratios, reducing statistical noise and faster attaining lower frequency uncertainties.

The precision of optical clocks also enables more accurate measurement of systematic shifts, reducing uncertainty and improving overall clock performance. Therefore, optical lattice clocks have the potential to offer a significant improvement over cesium atomic clocks in terms of precision, stability, and accuracy.

The World's First Adoption of an Optical Lattice Clock to Generate National Standard Time

The National Institute of Information and Communications Technology (NICT) became the first organization in the world to set the standard time using an optical lattice clock.

NICT has managed to reduce the difference (to five billionths of a second) between its generated time (Japan Standard Time) and Coordinated Universal Time (UTC) by adjusting the time interval to synchronize with an optical lattice clock.

This remarkable advancement combines the optical lattice clock with existing time generation technology, enabling NICT to maintain accurate time independently over extended periods without relying on GPS time or UTC.

This breakthrough will impact the second's redefinition in the SI Units and significantly reduce the need for frequent adjustments to maintain synchronization between Japan Standard Time and UTC.

Recent Research and Development

Ultraprecise Multiplexed Optical Lattice Atomic Clock

Physicists from the University of Wisconsin-Madison designed a novel multiplexed optical lattice clock with exceptional precision in measuring time differences. In addition, this clock can work with six separate clocks in the same environment, making it possible for the team to detect dark matter, test for gravitational waves, and delve into new physics with clocks.

The clock uses strontium atoms divided into multiple clocks in a vacuum chamber. The team could compare the number of atoms with excited electrons by simultaneously shining the laser on two clocks, enabling them to run experiments for longer periods.

The researchers wanted to measure how accurately they could distinguish differences between two groups of atoms in slightly varying environments, which affects their ticking rates.

They detected a difference corresponding to the two clocks disagreeing only once every 300 billion years, setting a new world for two spatially separated clocks.

Field Deployable and Compact Optical Lattice Clock Design

In recent years, the development of optical lattice clocks has shown great potential for advancing fields such as global communication, navigation systems, and even the redefinition of the standard unit of measurement. However, the size and sensitivity of current models have limited their deployment in the real world.

With support from the UK's Defense Science and Technology Laboratory, a group of quantum physicists has developed a novel approach to address these challenges. The team has created a robust and transportable design based on ultracold strontium atoms, with a small footprint of only 120 liters and a weight of less than 75 kg.

The design centered on an ultra-high vacuum chamber, smaller than any used before in quantum timekeeping. The team captured approximately 160,000 ultra-cold atoms within the chamber in under a second and transported the system over 200 km, with a setup time of fewer than 90 minutes.

This research opens up new possibilities for optical lattice clocks to be used in out-of-the-lab environments and has implications for various fields.

Future Outlooks

Optical lattice clocks offer unprecedented stability and accuracy, making them promising for future applications in various fields. For example, the technology has already contributed to fundamental physics tests and can potentially aid in the search for dark matter.

In the future, such clocks could be used for generating low-noise electronic signals, aiding in deep space navigation, and detecting fluctuations in gravitational potentials and gravitational waves. Additionally, the high sensitivity of optical clocks makes them ideal for detecting even small elevation changes, making them useful for geodesy applications.

As the technology matures, researchers are working to develop mobile optical lattice clock systems that can operate outside of the laboratory.

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References and Further Reading

NICT. (2022). The World's First Use of an Optical Lattice Clock to Keep National Standard Time. [Online]. Available from: https://www.nict.go.jp/en/press/2022/06/20-1.html#kiji1 (Accessed on 12 March 2023)

NIST. (2022). Optical Lattices: Webs of Light. [Online]. National Institute of Standards and Technology. Available from: https://www.nist.gov/physics/what-are-optical-lattices (Accessed on 12 March 2023)

Zheng, X., Dolde, J., Lochab, V., Merriman, B. N., Li, H., & Kolkowitz, S. (2022). Differential clock comparisons with a multiplexed optical lattice clock. Nature, 602(7897), 425-430. https://doi.org/10.1038/s41586-021-04344-y

Kale, Y. B., Singh, A., Gellesch, M., Jones, J. M., Morris, D., Aldous, M., ... & Singh, Y. (2022). Field deployable atomics package for an optical lattice clock. Quantum Science and Technology, 7(4), 045004. https://doi.org/10.1088/2058-9565/ac7b40

Oates, C. W., & Ludlow, A. D. (2015). Optical Lattice Clocks. [Online]. Optics & Photonics News. Available from: https://www.optica-opn.org/home/articles/volume_26/january_2015/features/optical_lattice_clocks/ (Accessed on 12 March 2023)

Orzel, C. (2022). What is an Optical Lattice, and Why Does it Make Such Good Clocks? [Online]. Forbes. Available from: https://www.forbes.com/sites/chadorzel/2022/02/17/what-is-an-optical-lattice-and-why-does-it-make-such-good-clocks/ (Accessed on 12 March 2023)

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Owais Ali

Written by

Owais Ali

NEBOSH certified Mechanical Engineer with 3 years of experience as a technical writer and editor. Owais is interested in occupational health and safety, computer hardware, industrial and mobile robotics. During his academic career, Owais worked on several research projects regarding mobile robots, notably the Autonomous Fire Fighting Mobile Robot. The designed mobile robot could navigate, detect and extinguish fire autonomously. Arduino Uno was used as the microcontroller to control the flame sensors' input and output of the flame extinguisher. Apart from his professional life, Owais is an avid book reader and a huge computer technology enthusiast and likes to keep himself updated regarding developments in the computer industry.

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