# Why a quantum computer simulation is not a quantum computer?

Is it because the inability to generate true random numbers (I dont think so) in the host machine or something else? My understanding is that the ability to emulate a quantum computer in a conventional one would eliminate the need for a real physical quantum computer if we can emulate Qbits and superposition . I know its not possible or very very very very difficult because researchers and companies are investing in real quantom computing but what is the real scientific reason. It seems google attempted that maybe because se from their perspective they have more programmers than physicists...

....... P. S. I used the terms simulation and emulation as different things so that the question reads "Why a Qbit simulatior is not an emulator" as in a Flight Simulator can be used to learn how to fly a plane but not to travel but lets say a casio calculator emulator running in a digital pc can be used to calculate whatever a real casio calculator can achieve.

It is possible to simulate quantum computers with classical computers. However, the time (and typically memory) needed for such a simulation will scale exponentially with the time a quantum computer needs. Thus, if a quantum computer needs $$10$$ times the computation time for a more complicated case, the simulation would need $$2^{10}$$ times more time, and so on. Conversely speaking, we believe that a quantum computer can solve certain problems with exponentially less effort than a classical computer (including a classical simulation of a quantum computer). Thus, we want a quantum computer and not only a classical simulation of a quantum computer: It should ultimately be exponentially faster in solving certain problems.