Upgrade backend to BackendV2 #44
Description
Without this change, the following error occurs when using a live backend with the example from the README:
qiskit.transpiler.exceptions.TranspilerError: 'Number of qubits greater than device.'
This is due to https://github.com/Qiskit/qiskit/blob/main/qiskit/compiler/transpiler.py#L485 not using the direct backend.coupling_map as it would if RigettiQCSBackend were based on BackendV2
A workaround for now is to call execute explicitly with the coupling_map argument like the following, as described in #43
job = execute(circuit, backend, shots=10, coupling_map=backend.coupling_map)