Reality: A universe of information 03 October 2012 by Michael Brooks Magazine issue 2884. Subscribe and save For similar stories, visit the Quantum World Topic Guide What we call reality might actually be the output of a program running on a cosmos-sized quantum computer Read more: “Special issue: What is reality?” WHATEVER kind of reality you think you’re living in, you’re probably wrong. The universe is a computer, and everything that goes on in it can be explained in terms of information processing. The connection between reality and computing may not be immediately obvious, but strip away the layers and that is exactly what some researchers think we find. We think of the world as made up of particles held together by forces, for instance, but quantum theory tells us that these are just a mess of fields we can only properly describe by invoking the mathematics of quantum physics. That’s where the computer comes in, at least if you think of it in conceptual terms as something that processes information rather than as a boxy machine on your desk. “Quantum physics is almost phrased in terms of information processing,” says Vlatko Vedral of the University of Oxford. “It’s suggestive that you will find information processing at the root of everything.” Information certainly has a special place in quantum theory. The famous uncertainty principle – which states that you can’t simultaneously know the momentum and position of a particle – comes down to information. As does entanglement, where quantum objects share properties and exchange information irrespective of the physical distance between them. In fact, every process in the universe can be reduced to interactions between particles that produce binary answers: yes or no, here or there, up or down. That means nature, at its most fundamental level, is simply the flipping of binary digits or bits, just like a computer. The result of the myriad bit flips is manifest in what we perceive as the ongoing arrangement, rearrangement and interaction of atoms – in other words, reality. According to Ed Fredkin of the Massachusetts Institute of Technology, if we could dig into this process we would find that the universe follows just one law, a single information-processing rule that is all you need to build a cosmos. In Fredkin’s view, this would be some form of “if – then” procedure; the kind of rule used in traditional computing to manipulate the bits held by transistors on a chip and operate the logic gates, but this time applied to the bits of the universe. Vedral and others think it’s a little more complex than that. Because we can reduce everything in the universe to entities that follow the laws of quantum physics, the universe must be a quantum computer rather than the classical type we are familiar with. One of the attractions of this idea is that it can supply an answer to the question “why is there something rather than nothing?”. The randomness inherent in quantum mechanics means that quantum information – and by extension, a universe – can spontaneously come into being, Vedral says. For all these theoretical ideas, proving that the universe is a quantum computer is a difficult task. Even so, there is one observation that supports the idea that the universe is fundamentally composed of information. In 2008, the GEO 600 gravitational wave detector in Hannover, Germany, picked up an anomalous signal suggesting that space-time is pixellated. This is exactly what would be expected in a “holographic” universe, where 3D reality is actually a projection of information encoded on the two-dimensional surface of the boundary of the universe (New Scientist, 17 January 2009, p 24). This bizarre idea arose from an argument over black holes. One of the fundamental tenets of physics is that information cannot be destroyed, but a black hole appears to violate this by swallowing things that contain information then gradually evaporating away. What happens to that information was the subject of a long debate between Stephen Hawking and several of his peers. In the end, Hawking lost the debate, conceding that the information is imprinted on the event horizon that defines the black hole’s boundary and escapes as the black hole evaporates. This led theoretical physicists Leonard Susskind and Gerard’t Hooft to propose that the entire universe could also hold information at its boundary – with the consequence that our reality could be the projection of that information into the space within the boundary. If this conjecture is true, reality is like the image of Princess Leia projected by R2D2 in Star Wars: a hologram. Michael Brooks is a writer and New Scientist consultant based in Sussex, UK http://bit.ly/SBuUxt