# Demonstrating MWI by interfering human simulations

TLDR: A demonstration that, given some reasonable assumptions, a quantum superposition of a brain creates an exponential number of independent consciousnesses, and each independent consciousness experiences reality as classical.

# The demonstration

I'm not going to explain the Many World's Interpretation of Quantum Physics, since much better expositions exist. Feel free to suggest your favourite in the comments.

Imagine we have the ability to simulate a conscious human in the future. This is almost definitely theoretically feasible, but it is unknown how difficult it is in practice.

I take it as obvious that a simulation of a conscious human will be conscious, given that it will answer exactly the same to any questions about consciousness as an actual human. So you should be as convinced it is conscious as you are about any other human.

Now we create a function that takes an input of length n bits and produces as an output whatever a given simulation responds to that input. For example the input could be an index into a gigantic list of philosophy questions, and the output would be whatever Eliezer Yudkowsky would have replied if you had texted him that question at exactly midnight on the 1st of January 2020.

We want to find the exact number of inputs that produce an output with a given property - e.g. the number of inputs that produce a yes answer, or the number where the answer starts with a letter from the first half of the alphabet, or whatever.

Classically it's obvious the only way to do this is to run the function 2^n times - once for every possible input, and then count how many have the desired property. Doing this will require creating 2^n separate consciousness, each of which live for the duration of the function call.

However, on a quantum computer we only need to run the function O(2^n/2) times using a quantum counting algorithm. So for example, if the inputs were 20 bits long, a classical computer would have to call the simulation function roughly a million times whilst the quantum computer would only use on the order of a thousand calls.

The way this works is by creating a superposition of all possible inputs, and then repeatedly applying the function in such a way as to create interference between the outputs which eventually leaves only the desired number.

So for any given property a simulation can exhibit, we can count how many of the 2^n possible simulations have that property in less than 2^n calls. And conceptually there's no possible way to know that without running every single possible simulation.

Now if you agree that anything which acts exactly the same as a conscious being from an input output perspective must in fact be conscious, rather than a philosophical zombie, it seems reasonable to extend that to something which act exactly the same as an aggregate of conscious beings - it must in fact be an aggregate of conscious beings. So even though we've run the simulation function only a thousand times, we must have simulated at least million consciousnesses, or how else could we know that exactly 254,368 of them e.g. output a message which doesn't contain the letter e?

The only way this is possible is if each time we ran the simulation function with a superposition of all possible inputs, it creates a superposition of all possible consciousnesses.

Now each of those consciousnesses produce the same output as they would in a classical universe, so even though they exist in superposition, they themselves see only a single possible input. To them it will appear as though when they looked at the input the superposition collapses, leaving only a single random result, but on the outside view we can see that the whole thing exists in a giant superposition.

This strongly mirrors how the MWI says the entire universe is in a giant superposition, but each individual consciousness sees a collapsed state due to decoherence preventing them interfering with other consciousnesses.