In a pair of advances reported this month, physicists have tested Einstein's equivalence principle in ways never before attempted — one team by measuring the quantum phase of a freely falling atom, the other by building an exotic particle beam…
An international team including Nobel laureate Sir Roger Penrose measured a freely falling atom's quantum phase for the first time, finding it matched Einstein's equivalence principle.science+1
Separately, ETH Zurich and the Paul Scherrer Institute created a controlled beam of muonium atoms to test whether exotic second-generation particles fall like ordinary matter.nature+1
The rubidium experiment confirmed Einstein's prediction but did not test whether gravity itself is quantum, leaving that question open for future work.scitechdaily+1