Posts Tagged ‘hidden variables’

Consensus Quantum Reality Revisited

January 16, 2013 2 comments


My last post was a little ranty, perhaps. So lets be fair to the physicists. What physicists mean by randomness is that when they run an experiment, unpredictable results are seen. Furthermore, when viewed in aggregate, these unpredictable results perfectly match probability distributions of a certain sort. And given that there are no parameters one can control in these experiments to predict what the answers will be, the reasoning goes that we might as well consider them as random, and build our theory accordingly.

This is fine, IMO, so long as you’re not trying to build an ultimate theory of physics. It’s a good idea, even, in the same way that spherical cows are a good idea. However, if you’re trying to get the answer right, and describe the smallest levels of physical existence, then, by definition, mere approximations won’t cut it.

However, this assertion, on its own, probably doesn’t say, or explain enough. For instance, what about Bell’s Inequality? Bell’s Inequality experiments absolutely rule out local realism. Local hidden variable theories simply can’t work. Isn’t that reason a strong indicator that there is inherent randomness in the universe?

In short, no. This is because I can simulate Bell’s Inequality results in the comfort of my own home without resorting to quantum randomness once. This is doable because Bell’s Inequality says nothing about non-local hidden variable theories.

The most well known of these is Bohmian mechanics, an approach that was first presented in 1927. This method has been thoroughly explored by physicists, but most of them walk away from it fairly unsatisfied, because it requires that every point in the universe can have instantaneous interactions with any other. The math of Bohmian mechanics is set up to ensure that the answer comes out exactly as it does for classic QM, while keeping the system deterministic. But, given that this doesn’t add any expressive power, and makes the model non-local, that feels like a fairly poor compromise.

Fair enough. But Bohmian mechanics isn’t the only way to build a non-local theory. As we’ve pointed out on this blog, if you’re looking for a background independent model of physics, you have to start thinking carefully about how spatial points are associated with each other. And if you follow this reasoning in a discretist direction, you generally end up building networks, whether you’re into causal set theory, loop quantum gravity, quantum graphity, or any of the other variants currently being explored.

And, as soon as you start looking at networks, it’s clear that there are perfectly decent ways of non-locally connecting bits of the universe that are not only self-consistent, but provide you with tools that you can use to examine other difficult problems in physics.

If I seemed to be disparaging physicists for not considering hidden determinism in the universe in my last post, that was not my intention. I certainly don’t mean to poke the finger at any specific individuals, but I do believe that poking the finger at the culture of physics in this regard is important.

We have experimental evidence of the non-locality of physical systems. However, we have no evidence that the universe runs on a kind of non-computable, non-definable randomness that flies in the face of what we know about information and the mathematics of the real numbers. Doesn’t that mean that we should be working a little harder to put together some modern deterministic non-local theories? Is it really better to hide under the blankets of the Copenhagen interpretation because this problem is hard?

After all, while issues of interpretation are broadly irrelevant given most of the day to day business of doing physics research, there is the small matter of quantum mechanics and relativity remaining unreconciled for the last hundred years. I would venture to propose that if we ever want to close that gap, having the right interpretation of quantum mechanics is going to be an important part of the solution.