ABSTRACT
Based on our discussion in Chapters 1 and 3, it appears that the field of atomic frequency standards is a rather mature field achieving precision and accuracy not reached in other fields of physics. However, in science, the challenge is always to attempt to do better. This is often driven by curiosity, but also with the hope of accomplishing greater precision and accuracy in measurement which may lead to verification, to higher levels, of predictions made by theories in parallel fields. Agreement with predictions is searched for and generally obtained. When this is so, our confidence in our theoretical model of the functioning of the universe is increased. However, very often, the results obtained in accurate and precise measurements do not agree with theoretical predictions and leads to a questioning of the basic physics that underlie our understanding of the accepted physical laws. This has happened quite often in the past. We may cite the expansion of the universe. Based on simple laws of attraction or relativistic curvature of the space-time canvas, the expansion should slow down. However, precise measurements on the electromagnetic radiation spectrum emitted by far-off galaxies have shown that the expansion actually accelerates with the passing of the millennia. This is totally contrary to our basic understanding of the physics involved and we do not yet have an explanation of the phenomenon (Vanier 2011). There are many other phenomena that have raised questions and these can often be answered by means of better measurements. For example, all our basic physical laws are based on the arbitrary introduction of parameters that we call fundamental constants. The actual stability with time of those constants is being questioned. Were they created at the same time as the original phenomenon that gave birth to our universe, the so-called big bang? Is it not possible that these constants have changed since the early days? As we will show later, we can answer to that kind of question to a certain level by means of atomic clocks. And this level depends on the precision reached with such atomic clocks. If it were only for that reason, we would be largely justified to attempt to develop still better clocks and reach a higher level of precision. There are, however, many other fields, where atomic clocks are used, fields that would profit from better accuracy and frequency stability of those clocks. We will outline them later. For the moment, following that short introduction on the need for better clocks, we will describe a new avenue in fulfilling that goal.
