“…This was first implemented for beams of Kr [25] and H 2 [26]. Subsequent developments [27,28] led to the realization of guides [29][30][31][32][33], velocity selectors [34], lenses [35], mirrors [36,37], beam splitters [38], accelerators and decelerators [39][40][41], and traps [40,[42][43][44][45]. These have been demonstrated for positronium, H, D, He, Ar, Kr, or H 2 .…”