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The equations of quantum physics have already been identified—that constitutes the theory behind them—but their solutions have not yet been found, and these are equally part of the theory. If the theory had already been solved, engineers could work with the solutions to develop new things.
Since the solutions are very difficult to obtain, simulations are necessary. Thus, simulations are used as a tool to explore the theory; however, this does not amount to using the theory itself in the form of a simulation.