Demonstration of universal time-reversal for quantum processes

Understand

Although the laws of classical physics are deterministic, thermodynamics gives rise to an arrow of time through irreversible processes.

• In quantum mechanics the unitary nature of the time evolution makes it intrinsically reversible, however the question of how to revert an unknown time evolution nevertheless remains.
• Remarkably, there have been several recent demonstrations of protocols for reverting unknown unitaries in scenarios where even the interactions with the target system are unknown.
• The practical use of these universal rewinding protocols is limited by their probabilistic nature, raising the fundamental question of whether time-reversal could be performed deterministically.