Figure 1
Illustration: Carin Cain

Figure 1: The spectrum of pulse trains from a mode-locked laser consists of a sequence of optical frequencies that are evenly spaced–an optical frequency comb. Pairs of frequencies formed from two “teeth” on the comb have a definite phase relationship with one another and the pair can control a spin qubit on a trapped ion via a stimulated Raman process. Hayes et al. extend this capability to any frequency by splitting the pulses and shifting each with an acousto-optic modulator.