Quantum Leaps, Long Assumed to Be Instantaneous, Take Time

The state to and from which the researchers are actually looking for quantum jumps is, meanwhile, the “dark” state — because it remains hidden from direct view. That ambiguity is crucial for maintaining quantum coherence during a jump between these two states. During that silent time, the system had presumably undergone a transition to the dark state, since that’s the only thing that can prevent flipping back and forth between the ground and bright states.

Source: www.quantamagazine.org