Noisy QPUs
Noisy gate-based Quantum Emulators are QPUs which take a noise model as parameter. These QPUs are intented to simulate noise effects, typically by storing information corresponding to the entire density matrix describing the quantum state of the emulated physical system. They are therefore the opposite of Ideal gate-based Quantum Emulators.
Additional inexactitudes can, depending on the simulator, be introduced by the method by which the quantum state/density matrix is stored. This marks the difference between Exact QPUs and Approximate QPUs.