Hey 👋🏼

Thanks for submitting this bug report. The cause for the exception is the (currently) underlying assumption of QMAP that the input circuit only consists of arbitrary single-qubit gates and CNOT gates, i.e., that the only supported two-qubit gate is the CNOT.
While the code doesn't complain currently, when another controlled-rotation gate is used in the circuit (such as a cs gate), it does throw an exception if a two-target gate is encountered. This is precisely what happens above in case of the QFT circuit, which contains SWAP operations at the very end.

There is an ongoing development in #235 for supporting arbitrary two-qubit gates. Once that is in, this example should work out-of-the-box. So I'll close this issue once #235 is merged.

For the moment, a possible workaround is to explicitly decompose the input circuit to basis gates, e.g., via

from mqt import qmap, bench
from qiskit.providers.fake_provider import FakeNairobi
from qiskit import transpile

arch = FakeNairobi()
qc = bench.get_benchmark(benchmark_name="qft", circuit_size=7, level="indep")
qc_basis_gates = transpile(qc, basis_gates=arch.configuration().basis_gates)
qc_mapped, res = qmap.compile(qc_basis_gates, arch, method="exact")

Note, however, that decomposition will most likely introduce further CNOT gates and increase the depth of the circuit, which makes the subsequent mapping problem harder/more complex. As a result, this can only be considered a temporary workaround that does not reflect the real performance.