With current state-of-the-art atomic clocks, physicists measure the oscillations of thousands of ultracold atoms. They do this multiple times, increasing their chance of accurately measuring the oscillations. (via PhysOrg) To improve this, the physicists at MIT used a time-reversal machine. Again, this isn’t really the type of thing you’d expect when hearing the words time machine.
But the machine allowed them to copy the evolution of the atom onto another atom. They could de-evolve another atom from here, forcing it back to its initial state. The entire process is somewhat intricate, but the basic gist is the scientists took two atoms and forced them to oscillate in a correlated state. Next, they took one of the atoms and forced it to de-evolve.
This essentially acted as a time-reversal mechanism for the second atom, showing them all the evolutions that the atom had made as it transformed back to its initial state. When measuring the difference between phases, they found notable changes, showcasing clear evidence that a quantum change had occurred somewhere in the atom’s evolution.
The physicists hope to be able to use this same technique on quantum sensors to aid in the hunt for evidence of dark matter and other phenomena.