Abstract
Atomic clocks are used constantly in daily life from synchronising
computer networks to GPS navigation, and after the redefinition of the
SI units in November 2018 accuratemeasurement of any physical
quantity will be dependant on our ability to make accurate clocks.
Based on the use of ultra-stable lasers to measure the electron
structure of individual atoms, optical atomic clocks are the most
accurate measurement devices ever created - up to 100 times more
accurate than the microwave caesium fountain clock that currently
defines the second - reaching fractional uncertainties of 1 part in
10
^18
. This accuracy is equivalent to counting the amount of sand on
all the beaches in the world, and getting the correct answer to within a
single grain, or keeping time accurate to one second in the lifetime of
the universe. However atomic clocks are not only useful for defining
measurement units; as tools for studying atomic structure they can also
be used for testing Quantum Mechanics and General Relativity, probing
for physics beyond what we currently understand. Clocks around the
world are hunting for dark matter, testing the Einstein Equivalence
Principle and searching to see if the fundamental 'constants' of nature
live up to their name.
In this talk I hope to provide an overview of current research into
optical atomic clocks: the systematic shifts
and environmentalperturbations which limit their accuracy and stability,
how this leads to the wide variety of atomic species under
investigation, how we verify that they are accurate, and finally how
people are trying to use them for both real-world applications and as
sensors for fundamental physics.