Thursday, December 26, 2013

Can we explain entanglement without supernaturalism?

By Mathew Goldstein

Is quantum entanglement supernatural magic?  We do not have to be a New Age mystic, or a fan of Chopra Deepak, to think so.  We do not know the spin of a particle until we measure it, yet the instant we know it's spin we also know the spin of its entangled partner particle which could, in theory, be millions of miles distant.  Naturalism's dependency on physicalism sometimes appears to impose too much of a constraint for a feasible explanatory framework.  People turn to supernaturalism in part because they perceive naturalism as too restricted, and therefore too weak, a framework to explain our universe.  Are they mistaken to do this?  Can quantum entanglement be explained within the constraints imposed by naturalism? 

Some intelligent and thoughtful people, such as philosophers Thomas Nagel, Massimo Pigliucci, David Albert, and others, express doubts that a naturalistic framework is sufficient.  Some skepticism is indeed appropriate when dealing with the mysterious and the unknown, as is the case here.  Nevertheless, contra the philosopher skeptics, and popular opinion, the better answer is that naturalism is likely sufficient, and one way to illustrate this is to highlight one such possible explanation.

Physics has sometimes advanced with "what if" thought experiments imagining extreme conditions that would be difficult to replicate in a laboratory, such as Einstein's thought experiment of chasing a light beam, leading to Special Relativity.  Two physics heavyweights, Juan Maldacena of the Institute for Advance Study in Princeton, and Leonard Susskind of Stanford University, California, recently asked this question:  What would happen if two black holes are entangled?

First, they showed that space-time tunnels emerge from quantum theory when two black holes are entangled. It's as if the wormhole is the physical manifestation of entanglement.  When space-time curves we experience that curvature as gravity.  Anytime an N dimensional object curves, it enters an N+1 dimension.  Given that space + time = 3+1 = four dimensions, gravity evidences a fifth dimension.  Such warping of space-time can produce space-time tunnels, or wormholes.

The two physicists then extended this idea to a single black hole and its Hawking radiation, resulting in a new kind of wormhole. This wormhole links a black hole and its Hawking radiation.  Hawking radiation is the result of the black hole absorbing the anti-particle and emitting the particle of the virtual particle - anti-particle pairs that are otherwise constantly bubbling into and out of existence in the vacuum of space.

Julian Sonner of MIT, Kristan Jensen of the University of Victoria, and Andreas Karch of the University of Washington decided to try to determine what happens with pairs of entangled particles. To see what geometry may emerge in the fifth dimension from entangled quarks in the fourth, these scientists employed holographic duality, a concept in string theory. They found that what emerged was a wormhole connecting the two quarks, implying that the creation of entangled quarks simultaneously creates a wormhole.

So while entangled particles are far apart in four dimensional space-time, they could be joined together, fragilely, in the fifth dimension.  Spooky action at a distance may not be what seems, it could be an illusion from our inability to directly observe the curvature of space-time.  We witness the curvature of space-time indirectly by its products of gravity, black holes, and quantum entanglement (physicists usually consider quantum mechanics to be more fundamental than gravity, so they may say that the curvature of space-time is a product of quantum entanglement).  

We cannot properly have confidence that this quantum entanglement with wormhole scenario is true without more favorable empirical evidence.  But even if this hypothesis proves to be false, the fact remains that a strictly naturalistic framework is rich with possibilities for explaining our universe.  The intuition that a naturalistic framework lacks the power to explain how our universe works repeatedly turns out to be mistaken.  We do not need to turn to supernaturalism to explain how our universe works.  With effort, time, observation, and ingenuity we continue to make progress naturally.

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