Page 54 - EETimes Europe June 2021

54 EE|Times EUROPE

SPECIAL REPORT: GPS/GNSS
Atomic Clocks Get Smaller, Lighter, More Precise

By John Walko

tomic clocks were first built and
used in the mid-1960s with the spe-
cific aim of redefining a split second
A — a definition that has stood the
test of time. The clocks worked by counting
the flipping frequency of the electron spins of
a cesium atom.
Hence, atomic clocks are incredibly
accurate, making frequency and time by far
the most precisely measured of all physical
quantities.
Atomic resonance is so sharp that it can
tell whether a standard quartz-crystal clock
deviates from the correct time by less than
1 part in 10 .
15
Several U.K. companies
and universities are
working collaboratively to

make atomic clocks more
accessible and practical
via improved accuracy and
miniaturization.

To achieve such high timing resolution,
atomic clocks make use of ultra-narrow
transitions in strontium atoms, providing
orders-of-magnitude–better performance
than their rubidium counterparts because of
their narrower atomic features.
In simple terms, the narrower the
atomic transition, the more accurate the
atomic clock.
That’s one key reason today’s satellite
navigation systems are so incredibly useful.
Indeed, some posit that without atomic
clocks, we would not enjoy the benefits (or
suffer the occasional frustrations) of GPS. Laser systems used in atomic-clock development
Some liken a GNSS satellite to a precise (Source: U.S. National Institute of Standards and Technology)
atomic clock hooked to a radio transmitting
a time signal. The timing data gets translated
into accurate three-dimensional location atomic clocks capable of measuring the vibra- As for GNSS location technology, several
information — latitude, longitude, and alti- tion of atoms, providing sufficient accuracy U.K. companies and universities are working
tude — as well as direction and speed. to detect phenomena such as dark matter and collaboratively to make atomic clocks more
Since the mid-1960s, scientists and gravitational waves. accessible and practical via improved accuracy
engineers have improved the accuracy each Bearing that in mind, we note that and miniaturization.
decade by an order of magnitude, and the physicists at the Massachusetts Institute of Kelvin Nanotechnology (Glasgow,
work continues apace. Technology recently built an atomic clock that Scotland), a specialist in advanced photonics
But most of the efforts to make atomic measures not a cloud of randomly oscillating and quantum components, is leading the
clocks more accurate — and, importantly, atoms, as the best designs now measure, but effort, partnering with Glasgow-based design
smaller and lighter —are not focused on atoms that have been quantumly entangled. house WideBlue and researchers from the
satellite navigation applications. For instance, That could open the door to a whole new Universities of Birmingham and Strathclyde.
there is increasing emphasis on designing world of quantum physics. Kelvin Nanotechnology will make the grating

JUNE 2021 | www.eetimes.eu