pytket to qiskit issue: Mutability of Gates

[onurdanaci]

Hi,

I was using pytket-qiskit package to get circuits between tket and qiskit via qiskit_to_tk and tk_to_qiskit functions. In particular, circuits involving CnZ gates in tket are so convenient, such that I was creating them in tket and transferring to qiskit.

Recently though some updates in tket, qiskit and pytket-qiskit packages created some issues. Some issues are simple, such as the nomenclatura changes from auto_rebases_pass to AutoRebase. But, some are more fundamental. The tk_to_qiskit function, upon encountering circuits involving CnZ gates, now returning the following error:

File [~/.pyenv/versions/jaxqml/lib/python3.12/site-packages/pytket/extensions/qiskit/qiskit_convert.py:1031](http://localhost:8888/lab/workspaces/auto-e/tree/Dropbox/aQa/aQa_codes/Class_H_Learn/shadow_first_hypergraph/pythonProject1/~/.pyenv/versions/jaxqml/lib/python3.12/site-packages/pytket/extensions/qiskit/qiskit_convert.py#line=1030), in tk_to_qiskit(tkcirc, replace_implicit_swaps, perm_warning)
   1028 supported_gate_rebase.apply(tkc)
   1030 for command in tkc:
-> 1031     append_tk_command_to_qiskit(
   1032         command.op, command.args, qcirc, qregmap, cregmap, symb_map, range_preds
   1033     )
   1034 qcirc.global_phase += param_to_qiskit(tkc.phase, symb_map)
   1036 # if UUID stored in name, set parameter uuids accordingly (see qiskit_to_tk)

File [~/.pyenv/versions/jaxqml/lib/python3.12/site-packages/pytket/extensions/qiskit/qiskit_convert.py:886](http://localhost:8888/lab/workspaces/auto-e/tree/Dropbox/aQa/aQa_codes/Class_H_Learn/shadow_first_hypergraph/pythonProject1/~/.pyenv/versions/jaxqml/lib/python3.12/site-packages/pytket/extensions/qiskit/qiskit_convert.py#line=885), in append_tk_command_to_qiskit(op, args, qcirc, qregmap, cregmap, symb_map, range_preds)
    884 if optype == OpType.CnZ:
    885     new_gate = qiskit_gates.ZGate().control(len(qargs) - 1)
--> 886     new_gate.name = "mcz"
    887     return qcirc.append(new_gate, qargs)
    888 if optype == OpType.CnRy:
    889     # might as well do a bit more checking

File [~/.pyenv/versions/jaxqml/lib/python3.12/site-packages/qiskit/circuit/singleton.py:312](http://localhost:8888/lab/workspaces/auto-e/tree/Dropbox/aQa/aQa_codes/Class_H_Learn/shadow_first_hypergraph/pythonProject1/~/.pyenv/versions/jaxqml/lib/python3.12/site-packages/qiskit/circuit/singleton.py#line=311), in _impl_init_subclass.<locals>.__init_subclass__.<locals>._Singleton.__setattr__(self, key, value)
    311 def __setattr__(self, key, value):
--> 312     raise TypeError(
    313         f"This '{self.base_class.__name__}' object is immutable."
    314         " You can get a mutable version by calling 'to_mutable()'."
    315     )

TypeError: This 'CZGate' object is immutable. You can get a mutable version by calling 'to_mutable()'.

I was wondering if you can fix this issue.

Best,
Onur

[cqc-alec]

Thanks for raising this issue. As it relates to pytket-qiskit I will transfer it to that repo...

[CalMacCQ]

Which version of pytket-qiskit, pytket and qiskit are you using? The following code works fine for the with the latest version of pytket-qiskit (0.63.0) If you could include code to reproduce your issue that would be great.

from pytket import Circuit, OpType
from pytket.extensions.qiskit import tk_to_qiskit

circ = Circuit(4).add_gate(OpType.CnZ, [0, 1, 2, 3])

qc = tk_to_qiskit(circ)

print(qc)

Output