Create Paulis of specific number of qubits

[dsvandet]

Consider trying to create the following Pauli on 100 qubits: Z0 or in product form IIIII...IIIIZ with 99 I's. If you do the following

Pauli("Z0")

you will get simply Z0 on one qubit. Instead, add the optional parameter num_qubits and do the following:

Pauli("Z_0", num_qubits = 100)

or

Pauli("Z", num_qubits = 100)

For Z_5 on 8 qubits the the code

Pauli("Z5", num_qubits = 8)

should produce the Pauli "IIZIIIII"

Note that you can do this in a Hack way by first creating

PauliList(["IIIIIIII", "Z5"])

and then extracting the Pauli of interest.

We should also add this functionality to PauliList.