It doesn't even need to be all that advanced. It needs to simulate only one perspective. Your perspective, or in my case, my perspective. All the rest could be simulated.
I could be simulated in your perspective. You could be simulated in my perspective. I think it can all be simulated on just one quantum computer. 4096 cubits should be sufficient.
By the way, the multiverse is written in a computer code that was developed in the 1940's.