Circuit can be composed of gate defined over different number of qubits?

[adamglos92]

It does not seem to be that big problem (everything works) but you can construct circuit with gate of different number of qubits. E.g. the code below runs without any problem

from monoprop import Circuit, ExpGate, MajoranaOperator, MajoranaPropagator

mop1 = MajoranaOperator({(0, 1): 1.0j}, 4)
mop2 = MajoranaOperator({(1, 0): 1.0j}, 5)
circuit = Circuit([ExpGate(mop1), ExpGate(mop2)], [1.0, 1.0], [0, 1])
majprop = MajoranaPropagator(mop1, [0, 1], cutoff=6)
majprop.build_graph(circuit)  # OK
MajoranaPropagator.from_circuit(circuit, mop2, cutoff=6)

Possible actions:

• keep us is (not a bug)
• delay decision for the future (not an issues for release IMHO)
• explicit checking inside Circuit for num_modes. Changes a bit concept of ExpGate not knowing about in what system size it lives