The funny thing is that, given in the story that it is possible to simulate the universe, even the top level Timmy and Diane can't be certain that they are not in a simulation, only that they are at the top of that particular line of simulations involving them. Imagine that when they publish this paper and others try Diane's program out on their own quantum computer, they will also create infinite simulations, which all also simulate this account of Diane and Timmy creating simulations at a previous point. In each of those infinite simulations of others running Diane's program there will be an infinite number of simulated Dianes and Timmys experiencing themselves as top level in the occurrence described in this story (not seeing the black ball behind them). Basically if the universe can be simulated, we are probably all in a simulation.
They'd probably know when they didn't see the hole in space behind them.
They probably wouldn't have any qualms with turning the simulation off either. My guess is that all those infinite simulations were on borrowed time until the top layer got bored.
I don't think you read my comment carefully enough (could be my fault, I may not have been very clear). Just to clarify, unless nobody ever runs Diane's program ever again on their own quantum machine there are an infinite number of Dianes and Tommys not seeing the black hole behind them even though they are also simulations, and they would not know it one way or the other but odds are they could guess they are in a simulation and would more than likely be right.
