How quantum entanglement really works and why we accept its weirdness

While scientists generally try to find sensible explanations for weird phenomena, quantum entanglement has them tied in knots.

This link between subatomic particles, in which they appear to instantly influence one another no matter how far apart, defies our understanding of space and time. It famously confounded Albert Einstein, who dubbed it “spooky action at a distance”. And it continues to be a source of mystery today. “These quantum correlations seem to appear somehow from outside space-time, in the sense that there is no story in space and time that explains them,” says Nicolas Gisin at the University of Geneva, Switzerland.

But the truth is that, as physicists have come to accept the mysterious nature of entanglement and are using it to develop new technologies, they are doubtful that it has anything left to tell us about how the universe works.

You can create quantum entanglement between particles by bringing them close together so that they interact and their properties become intertwined. Alternatively, entangled particles can be created together in a process such as photon emission or the spontaneous breakup of a single particle such as a Higgs boson.

The spooky thing is that, in the right conditions, if you then send these particles to opposite sides of the universe, performing a measurement on one will instantaneously affect the outcome of a measurement on the other, despite the fact that there can be no information exchanged between them.

For Einstein, this weirdness was an indication that something was missing from quantum theory.…