Quantum mechanics is universally considered to be so weird that, as Niels Bohr quipped, “if you are not shocked by it, you don’t really understand it.” One of the most shocking phenomena predicted by quantum mechanics is quantum entanglement, which Einstein called “spooky action at a distance.” He thought a more complete theory could avoid it, but in 1964 John Bell showed that if the predictions of quantum mechanics are true, then spooky action at a distance must indeed take place, given certain reasonable assumptions. Last week, in her article “Experiment Reaffirms Quantum Weirdness,” Natalie Wolchover reported that physicists are closing the door on an intriguing loophole related to these assumptions. This “freedom of choice” loophole had offered die-hards a possible way to avoid believing in spooky action at a distance.
This month’s Insights puzzle takes on the shocking weirdness of the quantum realm as implied by Bell’s theorem. It uses familiar objects and phenomena to reason about quantum particles in an intuitive way that, in my view, gets rid of the weirdness or at least shoves it out of sight so that the results don’t seem so strange at all. Is a simple physical model of quantum mechanics possible? Perhaps! You be the judge.
But first, let’s review Bell’s theorem and introduce our puzzle: