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Atomic Clocks Get Smaller, Lighter, More Precise

magneto-optical traps (MOTs) and compact The researchers reported that the device will eventually be integrated with an
collimation optics designed by WideBlue. clocks agreed with each another within ultra-compact atomic reference currently
Strathclyde will design the gMOT chip, and 1 part in 10 — sufficiently precise to detect under development.
18
Birmingham is responsible for testing the distortions in space-time continuum and The researchers hope to produce practical
prototype optical system. gravitational waves. atomic clocks within five years, working with
The collaboration focuses on scaling partners in the British aerospace industry.
an atomic clock by “reducing the optical MOBILE ATOMIC CLOCKS They will then focus on integrating the
constraints into scalable micro-fabricated Another research project seeks to eliminate technologies into portable atomic clocks
components as a critical step to bringing the need for satellites altogether. University and, eventually, consumer devices such as
laboratory performance out into real-world of Sussex researchers are developing what mobile phones.
applications,” said James McGilligan, senior they describe as portable atomic clocks that Consumer applications remain aspira-
research associate for the project at Kelvin could one day be integrated into mobile tional, however. “It could take another 20
Nanotechnology. phones, driverless cars, or drones. years to get there,” Pasquazi acknowledged
The project is scheduled to last about Using laser beam technology, the research- in an interview.
18 months. “While atomic clocks are already ers advanced the efficiency of a crucial “While my part of the project is pretty
remarkably accurate, we are focusing on element of an atomic clock — the lancet, advanced, and we are now seeking funds to
advanced micro-fabrication techniques and which is responsible for counting — by 80%, fabricate the chips, my colleagues looking at
improvements in laser-cooling optics to the team reported. the geolocation and navigation aspect[s] and
bring about significant reductions in the According to Alessia Pasquazi, a lead inves- developing a really efficient atomic refer-
size and weight of the next generation of tigator in the university’s Emergent Photonics ence and integrating that with the soliton
portable atomic clocks,” McGilligan told Laboratory, a portable atomic clock would device certainly have the bigger challenge,”
EE Times. enable access to mapping data when a user Pasquazi added.
David Burt, business development manager is driving through a tunnel or an urban area
at Kelvin Nanotechnology, said weight con- where satellite signal strength is weak. TERRESTRIAL GNSS
siderations remain the focus for atomic clocks Pasquazi said portable atomic clocks Obviating the need for GNSS satellites
used in satellite navigation systems. Still, “we would rely on an extremely accurate form of remains a challenge, and integrating
see many commercial opportunities in other geo-mapping, enabling access to a location everything at chip scale could prove equally
sectors, including defense, undersea oil, and and planned route without the need for a difficult. “We have produced prototypes that
mineral exploration,” he said. satellite signal. are perhaps the size of a shoebox, but that is
Paul Griffin, lead researcher with The reference, the equivalent of a pendu- already a big improvement on the size and
Strathclyde’s physics department, said the lum in a traditional clock, is derived from the weight of the current generation of atomic
project is “tackling head-on the difficult prob- quantum property of a single atom confined clocks being carried by all the navigation
lem of taking research-grade technology from in a chamber — the electromagnetic field of satellites,” Pasquazi noted.
the laboratory and into practical and scalable a light beam oscillating hundreds of trillions Either way, “we can definitely improve
quantum devices.” of times per second. The clock-counting the performance and security of next-
Griffin said atoms with complex internal element needed at such speeds is an generation GNSS systems, with much better
structures such as strontium and ytter- optical-frequency comb, a highly specialized time reference and navigation characteristics,
bium enable advances in the sensitivity of laser simultaneously emitting many colors, which could act at times of need as a kind of
quantum-enabled measurements of time and evenly spaced in frequency. independent backup,” she said.
gravity. “Over the last decade, our team at Micro-combs are very efficient in reduc- The growing need for a terrestrial GNSS
Strathclyde has shown how the technology ing the dimensions of frequency combs by alternative is highlighted in the latest in a
for laser-cooling alkali atoms can be reduced exploiting tiny optical micro-resonators, series of reports by the U.K.’s Royal Acad-
down to a simple handheld device powered but Pasquazi noted they are also extremely emy of Engineering. The report warns that
from a single battery.” delicate devices that are complex to operate “society may already be dangerously over-
The project also aims to develop new and therefore are difficult to use in practical reliant on satellite radio navigation systems.”
tools for laser cooling and manipulation of atomic clocks. Vulnerabilities range from signal jamming to
strontium atoms. “Our goal is that in five interference from solar flares.
years’ time, the core hardware for ultra-cold EFFICIENCY BREAKTHROUGH A significant failure of GPS could cause
strontium atoms will be an off-the-shelf com- The Sussex researchers claimed a break- numerous services to fail simultaneously,
ponent, which would be transformative for through with development of a high- including many assumed to be independent
not only timing but also for applications such efficiency micro-comb that exploits a special of each other, the study finds. Therefore, “the
as quantum computing,” said Griffin. type of wave called a laser cavity soliton. use of non-GNSS backups is important across
Solitons are particularly robust and can travel all critical uses of GNSS.”
CONNECTED CLOCKS unperturbed over very long distances. The academy recommends deployment of
In the U.S., physicists at the University of The Sussex team used pulses of light, widely available positioning, navigation, and
Colorado recently succeeded in connecting confined in a tiny cavity on a chip. timing (PNT) services as an alternative to
three optical clocks via laser beam between “The soliton that travels in this combi- GNSS. That step would help secure national
two buildings. nation has the benefit of fully exploiting infrastructure.
The clocks were based on strontium, the microcavities’ capabilities of generating A terrestrial radio navigation system called
ytterbium, and aluminum atoms. The many colors, while also offering the robust- eLORAN is among the terrestrial backup
strontium-based clock was located on the ness and versatility of control of pulsed options, according to the academy. ■
campus, while the others were housed 1.5 km lasers,” Pasquazi said.
away at the National Institute of Standards The next step is transferring the chip- John Walko is a technology writer and an
and Technology’s Boulder Laboratories. based technology to fiber technology. The EE Times contributing editor.

www.eetimes.eu | JUNE 2021