Quantum transitions take time – the news is its experimental demonstration

There is a different kind of “smooth” transition that a system can make between the 0 and 1 states, and that is via a
superposition of the two states. So to demonstrate the non-instantaneous nature of a quantum transition you have to do two things: first, you need to actually catch a system
during a (typically very fast) transition and second, you need to come up with a way of getting the system to interfere with itself (or producing some other indirect effect that would not occur but for the existence of a superposition). They used a superconductor to produce a macroscopic quantum system that behaved like an atom in that it had a small number of discrete energy levels that it could transition between.

Source: blog.rongarret.info