Both the precision control of trapped-ion systems and very large samples of cold neutral atoms are opening important new possibilities for quantum computation and simulation.
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.
Abstract : We have trapped large numbers of neutral atoms, and cooled them to millikelvin temperatures. Our next objective is to cool them to microkelvin temperatures. Dense samples of atoms cooled to microkelvin temperatures promise to open up new and exciting areas of physics. The lack of interaction of the low velocity atoms due to their reduced thermal motion, together with the possibility of indefinitely long interaction times, make samples of trapped atoms ideal for high resolution spectroscopy and for use as atomic frequency standards. Our main current effort in neutral atom trapping is cooling of trapped atoms to low temperatures. While this remains a difficult and elusive goal (to date, micro-kelvin temperatures have only been achieved with untrapped atoms), the rewards for supercooling trapped atoms appear to be high. The long confinement times, together with the reduced thermal motion of cold atoms, could result in a new era of ultra-high resolution spectroscopy and precise frequency standards. Potentially more exciting is the possibility of combining the high densities achievable in traps and the long deBroglie wavelength of ultra-cold atoms to observe novel quantum collective phenomena.