qiskit_to_tk does not work with exponentials in parameterized circuits

[ruihao-li]

Here is a minimal example in which I ran into error:

from qiskit import QuantumCircuit
from qiskit.circuit import Parameter
from pytket.extensions.qiskit import qiskit_to_tk

K = Parameter("K")
kappa = K.exp()
qc = QuantumCircuit(1)
qc.rz(kappa, 0)

tk_backend = IBMQBackend("ibm_nairobi")
tk_qc = qiskit_to_tk(qc)

The error message I got was:

RuntimeError: Unable to convert sympy expression exp(K)

I tested with other functions such as arccos(), log(), and so on and they all worked. It seems it is only the exponential that is giving the problem.
Is there a workaround for this? Thanks!

qiskit version: 0.44.2
pytket-qiskit version: 0.44.0

[CalMacCQ]

Thank you for making an issue. This definetly seems like a bug and something we should fix soon.

I can't immediately think of a workaround but if I do then I'll share it here.

[ruihao-li]

Thank you! Look forward to the fix!

[CalMacCQ]

Turns out this was caused by an issue with the bindings in tket itself. See the tket issue.

Fortunately this is now fixed in CQCL/tket#1069.

The fix will be in the next pytket release (coming soon) and the pytket-qiskit release is due shortly after.

Thanks again for rasing the issue.

[ruihao-li]

Awesome! Please feel free to close this issue.