Approximate QPUs
Approximate gate-based Quantum Emulators are QPUs which representation of the quantum state introduces approximations (we mean by that further inaccuracies than those inherent to floating point data for instance). They can be contrasted with Exact gate-based Quantum Emulators.
Some of these QPUs represent the evolution of a state vector, while others follow the evolution of an entire density matrix, authorizing the simulation of noise models. The former can be categorized as Ideal QPUs and the latter as Noisy QPUs.