There is a sci-fi book about scanning a human brain/conciusness to computer and testing wether it recognizes that the computer gets turned off between the tests

There is a sci-fi book about scanning a human brain/conciusness to computer and testing wether it recognizes that the computer gets turned off between the tests. Hint; it doesn't as it does not change state. Based on this experiment one can create a machine, upload his mind then destroy the machine because there will eventually be somewhere sometime a state of the universe where the state of the machine will proceed a step. So you can make a simulated world in that computer and be anything in that world, even god. Great mindfuck scifi, wish I could tell it's title but now it's clear the author read about this Boltzmann Brain theory...