Simulations by default are perfect. None of the imperfections one would see in a real quantum computer affect a simulation. However, we can artificially introduce errors in the simulation.
As of yet, QX Simulator supports one error model: the depolarizing channel.
Selecting the depolarizing channel error model introduces a random error in between each operation on a qubit. These errors are injected in a form of bit-flips (x error), phase-flips (z error) or both at the same time (y error). QX Simulator implements a “Symmetric Depolarizing Channel” using equal probabilities for x, y and z errors.
Here is an example of a simple Bell state experiment using the depolarizing channel error model with the per-operation error probability set to 0.001:
version 1.0 qubits 2 error_model depolarizing_channel, 0.001 prep_z q[0:1] H q CNOT q, q measure_all