Thing 1 sends a photon to Dick. Thing 2 sends a photon to Sally. They both send the other photons to the cat.
Dick and Sally measure their photons in whatever basis they choose.
Later, the cat decides whether or not to entangle the two photons it got.
If the cat did nothing, Dick and Sally's measurements have nothing to do with each other. There is no way they could talk to each other.
But if the cat did entangle them, the two measurements are correlated. That's weird, the cat acted in the future and influenced what Dick and Sally saw before.
An actual experiment
It reminds me of those time travelling neutrinos that came back and loosened that cable so they wouldn't be found out. (Credit Kate)
In what sense does the cat actually influence what happened earlier? The cat can entangle the photons, but they wouldn't have been entangled until it did so.
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