When passing a circuit to mctrajectory, pftrajectory and others, verify that it does not perform any unsafe operations

[ChenZhao44]

using QuantumClifford
using QuantumClifford.ECC

circ = [
    sHadamard(1),
    sCNOT(1, 2),
    sMZ(1),
    sMZ(2),
]

frames = PauliFrame(10, 2, 2)
pftrajectories(frames, circ)

sMZ(1) and sMZ(2) will cause an out-of-bounds behavior that could crash the program without throwing an error. This is because they are equivalent to sMZ(1, 0) and sMZ(2, 0) and will try to access index 0. I recommend changing the default parameter of bit to 1 instead of 0. Ideally, it would be better to check the indices in pftrajectories for the circuit we are going to simulate before calling apply!.

[Krastanov]

@ChenZhao44 , this is now fixed -- if the index is 0, it is simply not saved anywhere. The default of 1 would also be unsafe, because there is not guarantee that a frame would have allocated even one bit of space for classical memory. I will leave this open as a general issue for "preprocess circuits to verify they do not have unsafe or undefined operations". It should probably be a part of the compactifation pass.