How Quantum Physicists ‘Flipped Time’ (and How They Didn’t)

Physicists have coaxed particles of light into undergoing opposite transformations simultaneously, like a human turning into a werewolf as the werewolf turns into a human. In carefully engineered circuits, the photons act as if time were flowing in a quantum combination of forward and backward. “For the first time ever, we kind of have a time-traveling machine going in both directions…

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