Extended Data Fig. 2 | Beryllium ion f luorescence during one preparation–
spectroscopy cycle. Spectroscopy (terahertz wave on) occurs during the
interval marked ‘REMPD’. Beryllium laser cooling is on all the time. SE, secular
excitation. B, a magnetic f lux strength B is applied during REMPD. B 0 , a
strength B 0 is applied for rotational laser cooling. CPS, counts per second. The
signal obtained from the spectroscopy cycle is indicated in cyan.