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If you follow such things, you might be interested to read about an effort by a University of Washington researcher to demonstrate what is known as “quantum retrocausality” – in other words, backwards causation.

Here’s the idea. When two quantum particles are related in a way known as “entanglement”, their states are linked, regardless of how far apart they are. Quantum measurements are probabilistic: for example, if you measure a certain particle’s spin, it might have an equal chance of taking an “up” or “down” value. There’s no “fact of the matter” in advance of the measurement; it’s a roll of the dice. But if the particle has a complementary, entangled partner, then as soon as you measure particle A’s spin you know that particle B will have the opposite value, regardless of their spacetime separation. It’s as if particle A instantly “signals” particle B about which value it must take. So couldn’t we use this bizarre feature of the world to send faster-than-light signals? Well, no, as it turns out, due to the fact that the measured values of the particles are random to begin with: all that is correlated are the values at the two ends of the system; but at each end all an observer sees is a random pattern. It’s not until the two sets of measurements are brought together and compared — something that has to be done at sub-light speeds — that the entanglement shows its hand.

But it ain’t necessarily so, says Dr. John Cramer. He is putting together an experiment that might make it possible to influence the outcome of a measurement by a decision made afterwards. Learn more here.

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