fidelity analysis

[Roger-luo]

write up a fidelity analysis by interpreting the move program + gates, we can begin with a single lattice member in the lattice and extend to union etc. to support feedforward

class Forward(..):
    state: FidelityLattice

    ... # do the interp stuff


# update the state by joining the global state in method table
class MethodTable(...):
    @interp.impl(gate.X)
    def impl_X(self, interp, frame):
        interp.state.join(whatever)
        return ()


class FidelityLattice:
    pass

class Fidelity(FidelityLattice):
    data: float

cc: @weinbe58 will help you get started