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A View from **Emerging Technology from the arXiv**

## How Entanglement Could Be Deterministic

A Nobel Prize-winning physicist has developed a model of the universe as a cellular automaton that allows entanglement to be deterministic.

The universe is cellular automaton in which reality is simply the readout of a giant, fantastically complex computing machine. That’s the conclusion of Nobel Prize-winning physicist Gerard ‘t Hooft, who says this also means that quantum mechanics is a deterministic theory.

The key new feature of this deterministic model is that it specifically allows for the quantum phenomenon of entanglement.

One of the greatest scientific debates in history was fought over the nature of quantum mechanics and the troubling consequences of a theory that is first probabilistic rather than deterministic (God does not play dice) and second nonlocal, meaning it allows the spooky action at a distance of entanglement.

One way of resolving this problem is to assume that quantum mechanics is an incomplete description of reality and that a full, deterministic description can be achieved using some additional hidden variables. One theory, for example, supposes that one hidden variable is a quantum particle’s position.

Another idea is that spooky action at a distance can be explained by hidden variables that determine in advance how entangled particles will behave when measured.

However, hidden variable theories have been largely discounted by quantum theorists because their mathematical structure leads to a prediction about the correlations between entangled particles that has been shown to be wrong in numerous experiments. By this analysis, hidden variable theories cannot underlie quantum mechanics.

But there may be classes of hidden variable theories that are not covered by this argument.

Today, ‘t Hooft said he has found one of them: a new class of deterministic models of the universe that allow for entanglement. Curiously, these are based on cellular automaton, a computing device consisting of a grid of cells that can be in various states depending on the states of the adjoining cells.

He’s not the first person to create a model of the universe out of a cellular automaton. Independent scientist Stephen Wolfram believes the universe is better modeled by cellular automata than by the conventional laws of physics. Ed Fredkin, a computer scientist at MIT, has put forward a similar idea. And mathematician John Conway famously developed the Game of Life based on a cellular automaton.

So ‘t Hooft is in good company.

However, his model has a number of deficiencies of which he seems to be well aware. Perhaps the most serious is that the model lacks many of the most basic symmetries that our universe enjoys, such as rotational symmetry.

But ‘t Hooft counters by saying, “One could argue that symmetry arguments should not enter into the discussion of the interpretation of quantum mechanics.” Although how you can make this argument isn’t clear.

I think it’s fair to say that ‘t Hooft’s ideas do not enjoy widespread support. On the other hand, that is no real measure of their efficacy. The real question is whether ‘t Hooft can make any predictions that would allow other scientists to put his model to the test.

Ref: arxiv.org/abs/0908.3408: Entangled Quantum States in a Local Deterministic Theory