Wednesday, March 16

Quantum Mechanics and Free Will


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A conjecture called superdeterminism, outlined decades ago, is a response to several peculiarities of quantum mechanics: the apparent randomness of quantum events; their apparent dependence on human observation, or measurement; and the apparent ability of a measurement in one place to determine, instantly, the outcome of a measurement elsewhere, an effect called nonlocality.

Einstein, who derided nonlocality as “spooky action at a distance,” insisted that quantum mechanics must be incomplete; there must be hidden variables that the theory overlooks. Superdeterminism is a radical hidden-variables theory proposed by physicist John Bell. He is renowned for a 1964 theorem, now named after him, that dramatically exposes the nonlocality of quantum mechanics.

Bell said in a BBC interview in 1985 that the puzzle of nonlocality vanishes if you assume that “the world is superdeterministic, with not just inanimate nature running on behind-the-scenes clockwork, but with our behavior, including our belief that we are free to choose to do one experiment rather than another, absolutely predetermined.”

In a recent video, physicist Sabine Hossenfelder, whose work I admire, notes that superdeterminism eliminates the apparent randomness of quantum mechanics. “In quantum mechanics,” she explains, “we can only predict probabilities for measurement outcomes, rather than the measurement outcomes themselves. The outcomes are not determined, so quantum mechanics is indeterministic. Superdeterminism returns us to determinism.”

“The reason we can’t predict the outcome of a quantum measurement,” she explains, “is that we are missing information,” that is, hidden variables. Superdeterminism, she notes, gets rid of the measurement problem and nonlocality as well as randomness. Hidden variables determine in advance how physicists carry out the experiments; physicists might think they are choosing one option over another, but they aren’t. Hossenfelder calls free will “logically incoherent nonsense.”

Hossenfelder predicts that physicists might be able to confirm superdeterminism experimentally. “At some point,” she says, “it’ll just become obvious that measurement outcomes are actually much more predictable than quantum mechanics says. Indeed, maybe someone already has the data, they just haven’t analyzed it the right way.” Hossenfelder defends superdeterminism in more detail in a technical paper written with physicist Tim Palmer.  

AUTHOR  -  John Horgan directs the Center for Science Writings at the Stevens Institute of Technology. His books include The End of Science, The End of War and Mind-Body Problems, available for free at mindbodyproblems.com. For many years he wrote the popular blog Cross Check for Scientific American.


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