The question of whether the universe is really an elaborate, multi-dimensional simulation has been around for a number of years. In a conjecture published some ten years ago, Nick Bostrom considered whether the universe and everything within it (including stars, galaxies, planets and human beings.) is one massive, virtual simulation- a vast and intricate hyper quantum computer program being run from outside- perhaps by an extraordinary intelligence..
In addition, given all entities are mostly empty space anyway, ultimately predicated on quantum wave forms or wave functions, one can easily see how the ability to manipulate quantum units at will could lead to a simulation of an entire universe. In fact, if one builds consistently on quantum mechanics one can theoretically arrive at all the macroscopic laws of nature that we see govern our universe. For example, in the limit of the quantum number n ® ¥, quantum mechanics converges to Newtonian mechanics, so this rule like others (e.g. Bohr's Complementarity Principle, Heisenberg's Uncertainty Principle, conservation of mass-energy etc.) can easily be built into the simulated system.
In a sense, if the universe is simulated, then we and all other life forms within it are avatars. And as fanciful as that sounds, some philosophers have long argued that we are more likely to be artificial intelligences, or 3D virtual representations, trapped in a fake universe, than we are to be organically-based minds in a real one. Of course, if these philosophers are correct, then admittedly the concept of a natural afterlife (see previous blog posts from Feb. 9, 10) might be feasible. The reason is that, if the cosmos is a virtual simulation then the very laws of physics (e.g. entropy law) that allow us to devise reality-checking technology and measurements, might have little to do with the rules that govern the meta-cosmos inhabited by our simulators. In other words, if they wish to suspend the 2nd law of thermodynamics to enable a perpetual dream state at death, they can do so. (But this is the only way I could see that afterlife working!)
But how would one know it or prove it? First things first: Is this equivalence of physical body and cyber-body (avatar) going too far? I don't believe so. The cyber-body is ultimately composed of moving electrons and quanta (photons) that cause multiple pixels on the monitor screen to vary in intensity, producing the illusion of motion. By the same token, the physical body is ultimately constituted of electrons, and can receive and process photons, e.g. by the optic nerve. On a quantum mechanical level the two bodies are very nearly the same. The differences appear at the gross or macroscopic levels, where the physical body displays a 3-dimensional solidity and differentiation of organs, tissues and cells. But are these fundamental? Who can say? It depends on the constructions, doesn't it?
Assuming clever enough simulations, say using quadrillions of quantum spin system gates operating in tandem, arguably no one would know the difference. In 1982, the Nobel-winning physicist Richard Feynman made a notable (and as it turns out, prescient) observation concerning a “universal quantum simulator”. Feynman conjectured that to obtain 300 nuclear spins, the quantum simulator would need only 300 quantum bits or qubits. So long as one could program the interactions between qubits so that they emulated the interactions between the 300 nuclear spins, the dynamics would be simulated.
Was Feynman off his rocker? Not really! As it turns out one of the best ways to generate simulations via a quantum computer is to use nuclear spins. To see how this could work, study the accompanying diagram with three versions of nuclear spin – to which each is assigned a wave state vector in bracket form. In this case, the nuclear spin down state corresponds to 1>, the spin up state to 0> and there is a combined state: 0 > + 1 >.. (The last is a state of spin along the axis perpendicular to the spin-axis).
More to the point, the latter superposition illustrates the property of quantum parallelism: the ability to compute or register two states simultaneously, which is impossible for normal computers (which register 0 OR 1, never both at one time – unless they are in glitch mode!) Thus, a quantum computer can manipulate two bits (qubits) at one time. If there are a trillion such qubits, each can potentially register 1 and 0 in combined wave bracket states, simultaneously. It should also be easily seen that this combined wave state is the analog of the superposition of states seen in the electron double slit experiment, e.g. for
y = y1 + y2
y = y1 + y2
Any qubit in a state (0) can be placed in the double-qubit state by rotating it one fourth of a turn (as evident from inspection of the diagram) Much more fascinating (and to the point) is that if another qubit is introduced into the scene - say with the same wave state 0> its presence can “flip” the original qubit , effectively producing a quantum-controlled NOT operation which acts like a classical NOT gate. It is billions and billions of such logic gates which form the basis of computing. Given that qubits also hold much more information than ordinary bits, it is easy to see that if such nuclear spins can be used in the sort of logic gate manner described, one can have the basis for a quantum computer.
If one can have such an entity, then one could simulate just about anything. To use the words of Seth Lloyd :
A quantum computer that simulated the universe would have exactly as many qubits as there are in the universe, and the logic operations on those qubits would exactly simulate the dynamics of the universe.
Because the behavior of elementary particles can be mapped directly onto the behavior of qubits acting via logic operations, a simulation of the universe on a quantum computer is indistinguishable from the universe itself
This is a profound statement! It implies that if the universe were indeed a mammoth simulation we’d likely never be able to prove it. But.....what if the simulators, analogous to human beings, aren't 'gods' or perfect? Then it is feasible an imperfect copy of the universe may be running, just good enough to fool most of its inhabitants - at least until they evolved the brain power to conceive applicable tests.
A breakthrough came in 2007, when John D. Barrow, a professor of mathematical sciences at Cambridge University first suggested that an imperfect simulation of reality would contain detectable glitches. Just like this computer I'm now using to blog, the universe's operating system would need updates to keep working. As the simulation degraded, Barrow observed, we might see aspects of nature that are supposed to be constant, i.e. the speed of light, or the fine structure constant, inexplicably 'drift' from their stable values.
Two years ago, Silas Beane and colleagues at the University of Washington, suggested a more concrete test of the simulation hypothesis. Most physicists assume space is smooth and extends out infinitely. But cosmologists modeling the early universe cannot easily re-create a perfectly smooth background to contain their atoms, stars and galaxies. Instead, they build up their simulated space from a lattice or grid, just as television images are comprised of multiple pixels.
Silas' team calculated that the motion of particles within their simulation, and hence their energy, is related to the distance between the points of the lattice: the smaller the grid size the higher the energy of particles can be. That means that if our universe is a virtual simulation, we will observe a maximum energy for the fastest particles.
As it happens, astronomers have observed that cosmic rays - high speed particles that originate in far flung galaxies- always arrive at Earth's vicinity with a specific maximum energy of about 1020 electron volts. Recall that: 1.6 x 10-19 J = 1 eV
So that: 1020 eV = 1020 eV (1.6 x 10-19 J / eV )= 16 J
Another aspect comes to attention: IF space is continuous there is no underlying grid that guides the direction of cosmic rays. In other words, their direction ought to be isotropic - or coming from all directions, equally. Thus, a major test that we live in a simulated cosmos would be a non-isotropic distribution of cosmic rays. It is premature to make any decision here, since astronomers need much more cosmic ray data to make the case one way or the other.
In the meantime, does it make a difference, really - if the cosmos is virtual or real? Not to me. Other than that I would hope that the virtual simulators, whoever or whatever they are, wouldn't manipulate the 'game' too much! (I.e. programming in 'demonic' possessions to make certain twits believe demons are real.) Oh, and if they would, I'd rather they pass on letting me have a "natural afterlife"!
 Lloyd: Programming the Universe, 154.