## Thursday, March 18, 2010

### Is the Universe a Simulation? (II)

The Quantum computing basis of a Universe simulator :

In 1982, the Nobel-winning physicist Richard Feynman made a notable (and as it turns out, prescient) observation concerning a “universal quantum simulator”. Feynman speculated 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

U = U1 + U2

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. (See diagram – Fig, 2)

As readers will recall, 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 (‘Programming the Universe’, p. 154):

“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.”

And further (ibid.)

“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 or see outside of it. To us, locked inside as quantum simulations - interacting dynamically with millions of other such simulations, it would all appear quite real. But what is real? We think we know, but in fact not. Most people aren’t even remotely aware that they’re mostly empty space. They may have heard that said before, but the fact they can press a hand to their arm and not see it go right through (because of the repulsive electro-magnetic forces acting at the surfaces) means they don’t take it literally. How could they?

Let's do a thought experiment. Imagine yourself sitting in front of a computer monitor in which a virtual game (like the SIMS) is being run. Now, without touching anything on the keyboard, imagine yourself actually inside the display, interacting directly with the various virtual denizens. Not merely looking from outside. Actively project yourself into that virtual reconstruction (imaginary time displacement). What would you see? Hear? Feel? Think?

You experience this world. You can be pursued by its various beasts, confronted by its more obstreperous human inhabitants, hear them screeching or bleating and get hurt by them as well. You are inside the virtual world! You are also subject to its laws, its imperatives - unless, you can be granted a liberating revelation. A revelation that allows you to master its influences from within, and control others' perceptions as well.

It is a thought that infinitely regresses you from outside the display to the inside:

“I am thinking of myself, in the display- thinking of myself in a display within the display; thinking of myself within a display of the display of the display...” .etc. ad infinitum

A crucial point, in this regard, has been noted by Alex Comfort:[1]

"In treating mind, though virtual, as a separate explicate, Buddhist and many Hindu philosophers tend to share a radical view of reality which asserts that since all conventional phenomena are illusory, anyone who adequately masters his own illusion of the phenomenal can manipulate it and other people's experience practically at will."

In other words, if one can see the simulation of the universe as the artifact it is, and thereby master his or her own perceptions (misperceptions?) then it is possible to manipulate it at will using one’s mind. Lloyd in his perceptive book notes that the backdrop to all the super-quantum computer calculations is the quantum fluctuation. As one manifestly masters his perceptions, and sees that indeed all conventional phenomena are illusory then he can induce his own quantum fluctuations at will, and thereby manipulate (re-program?) “reality”.

Here’s the paradox: why would one wish to do that, except to attain or use power which very thing the nonlocal philosophy militates against?

Next: Is There Evidence for a Universe Simulation?

[1] Comfort, A.:1984, Reality and Empathy: Physics, Mind & Science in the 21st Century, State University of New York Press, Albany, p. 41.