Scientists from Vienna published a paper on their experimental proof of time reversal processes in optics
Demonstration of universal time-reversal for qubit processes
"n this work, we have demonstrated a universal time-rewinding protocol for two-level quantum systems. Unlike previously proposed protocols, ours can reach an arbitrarily high probability of success and is asymptotically optimal in the time required to perform the rewinding, answering the question of whether or not such processes are permitted by the laws of quantum mechanics. Remarkably, the experimenter performing the rewinding does not need any knowledge about the target quantum system, its internal dynamics, or even the specifics of the perturbed evolution. The optimality of the protocol is demonstrated in our implementation, where the total elapsed time (equivalent to the number of applications of 𝑈) grows linearly with the length of time to be rewound, with an optimal proportionality constant of one. We find that the experimental quantum protocol significantly outperforms the optimal classical strategy in terms of the resulting state fidelity.
We emphasize that our results are in principle not restricted to photonic quantum systems, since the concepts used do not make any assumptions about the physical system the protocol is applied to."...