If we assume it is possible to simulate a universe. A piece of hardware with just enough power to simulate one universe will eventually be simulating an infinite amount of them, through more of these machines being built inside of the simulated universes.
The stimulated universe has to be smaller than the universe so you have a finite amount of universe in universes until one universe gets to small to stimulate an universe
in a simulation of an universe i need to save every position of every particle and additionally the rules how they interact (e.g. the speed of light or two electrons push each other) the biggers computer inside the simulation would be made by all particles of the simulated universe (*)
Maybe the proper form of the idea you're raising is that if a computer is able to simulate itself to a tee and a bit more then we can have infinite processing power by using all of those little bits of excess power.
it can simulate approximately. According to wikipedia, "... the use of simplifying approximations and assumptions within the simulation ..." Therefore it's not true that the hardware needs to have infinite power.
It can be assumed that if it is a perfect simulation of our universe, then the quantum computer that was created in the original universe would eventually be created in the simulated universe causing a sort of cascading effect of infinite simulated universes.
Since this is a quantum computer we are talking about, the amount of power required would only have to be enough to simulate one universe. In the simulated universe, those being simulated would have to have enough power to simulate another universe in a quantum computer. The result being that each
simulated universe only has to deal with getting enough power for their quantum computer. The parent universe won't have to worry about trying to get infinite power since they aren't the ones simulating a universe within a universe. It's their simulations that are simulating a universe, therefore it's only the simulations that will have to deal with finding enough power for their quantum computing simulation. Ad infinitum.