ORC Seminar Series

“Optical Atomic Clocks”

Speaker: Professor Patrick Gill, National Physical Laboratory

Date: 1 July 2009

Time: 2pm       

Venue: B53 Seminar Room


The microwave caesium atomic clock has formed an enduring basis for the SI second over the last few decades. The advent of laser cooling has underpinned the development of the cold caesium fountain clock, which demonstrates a frequency uncertainty of 1 part in 1015 per day. Since the turn of the century, the pace of research into alternative atomic clock technologies based on optical clocks has quickened considerably, such that they now challenge Cs fountain clock performance. This has been achieved in part by the arrival of femtosecond combs which allows high-accuracy inter-relation between microwave and optical frequencies.

Optical clocks are based on state-of-the-art frequency-stabilised lasers probing very weak absorptions in a single cold trapped ion held in an electromagnetic trap or in an ensemble of cold atoms trapped within an optical lattice. This talk will aim to contrast the performance of trapped ion and optical lattice neutral atom clocks with the caesium fountain, discuss issues in remote high-accuracy clock comparison and point to future opportunities and applications.


After completing his D.Phil in experimental laser physics at the Clarendon Laboratory, University of Oxford, Patrick joined NPL in 1975 as a research scientist working on laser stabilisation techniques. In 1984 he became the Head of optical wavelength standards, an NPL Fellow in 1992, and Senior NPL Fellow in 1997.

His research at NPL covers the development of laser-cooled trapped ion systems, both for application as optical clocks and optical frequency standards, and as well-defined and isolated quantum systems for the study of entanglement techniques in quantum information processing. In parallel with the trapped ion optical frequency standards research, he is concerned with high-accuracy optical frequency metrology using wide-span mode-locked femtosecond laser combs. Associated interests include narrow sub-Hz linewidth solid-state laser oscillator development, diode laser spectroscopy and acetylene-stabilised lasers for optical communication frequency standards.

In 1999 he became a Visiting Professor at the Dept of Physics, Imperial College London, and also a Visiting Professor in the Dept of Physics, University of Oxford in November 2006.

Prof. Gill is a Fellow of the Institute of Physics. In 2007, he received the IEEE International Frequency Control Symposium I I Rabi Award and in 2008, the IOP Thomas Young medal.

Copyright University of Southampton 2006