  Recent progresses on quantum control of cold atoms and trapped ions in both
the scientific and technological aspects greatly advance the applications in
precision measurement. Thanks to the exceptional controllability and
versatility of these massive quantum systems, unprecedented sensitivity has
been achieved in clocks, magnetometers and interferometers based on cold atoms
and ions. Besides, these systems also feature many characteristics that can be
employed to facilitate the applications in different scenarios. In this review,
we briefly introduce the principles of optical clocks, cold atom magnetometers
and atom interferometers used for precision measurement of time, magnetic
field, and inertial forces. The main content is then devoted to summarize some
recent experimental and theoretical progresses in these three applications,
with special attention being paid to the new designs and possibilities towards
better performance. The purpose of this review is by no means to give a
complete overview of all important works in this fast developing field, but to
draw a rough sketch about the frontiers and show the fascinating future lying
ahead.
