The manipulation of neutral particles*

The written version of my lecture is a personal account of the development of laser cooling and trapping. Rather than give a balanced history of the field, I chose to present a personal glimpse of how my colleagues and I created our path of research. I joined Bell Laboratories in the fall of 1978 after working with Eugene Commins as a graduate student and post-doc at Berkeley on a parity nonconservation experiment in atomic physics (Conti et al., 1979; see also Chu, Commins, and Conti, 1977). Bell Labs was a researcher’s paradise. Our management supplied us with funding, shielded us from bureaucracy, and urged us to do the best science possible. The cramped labs and office cubicles forced us to rub shoulders with each other. Animated discussions frequently interrupted seminars, and casual conversations in the cafeteria would sometimes mark the beginning of a new collaboration. In my first years at Bell Labs, I wrote an internal memo on the prospects for x-ray microscopy and worked on an experiment investigating energy transfer in ruby with Hyatt Gibbs and Sam McCall as a means of studying Anderson Localization (Chu, Gibbs, McCall, and Passner, 1980; Chu, Gibbs, and McCall, 1981). This work led us to consider the possibility of Mott or Anderson transitions in other exciton systems such as GaP:N with picosecond laser techniques (Hu, Chu, and Gibbs, 1980). During this work, I accidentally discovered that picosecond pulses propagate with the group velocity, even when the velocity exceeds the speed of light or becomes negative (Chu and Wong, 1982). While I was learning about excitons and how to build picosecond lasers, I began to work with Allan Mills, the world’s expert on positrons and positronium. We began to discuss the possibility of working together while I was still at Berkeley, but did not actually begin the experiment until 1979. After three long and sometimes frustrating years, a long time by Bell Labs standards, we finally succeeded in exciting and measuring the 1S-2S energy interval in positronium. (Chu and Mills, 1982; Chu, Mills, and Hall, 1984).