Replace bit condition “c_if” in bit-string condition “if_test” of "qiskit_convert.py"

[yoshi-qc]

In “tk_to_qiskit”, a conditional gate in TKET circuit transpires a conditional gate of qiskit circuit using bit condition “c_if” on L660-L697 of “qiskit_convert.py”.
https://github.com/CQCL/pytket-qiskit/blob/main/pytket/extensions/qiskit/qiskit_convert.py
https://docs.quantum.ibm.com/api/qiskit/qiskit.circuit.InstructionSet#c_if
I found that bit-string condition “if_test” is currently supported and recommended in qiskit. Should we edit the lines L660-L697 of “qiskit_convert.py”?
https://docs.quantum.ibm.com/api/qiskit/qiskit.circuit.QuantumCircuit#if_test

pytket-qiskit/pytket/extensions/qiskit/qiskit_convert.py

Line 660 in 9417469

if optype == OpType.Conditional:

[yoshi-qc]

The conditional phase is supported in qiskit circuit.

pytket-qiskit/pytket/extensions/qiskit/qiskit_convert.py

Line 662 in d5b00fc

# conditional phase not supported

For instance,

with qc.if_test((bits[4], 1)):
    qc.append(GlobalPhaseGate(1),[],[])

https://docs.quantum.ibm.com/api/qiskit/qiskit.circuit.library.GlobalPhaseGate

Should we make another issue?

[cqc-alec]

@yoshi-qc what is the priority on this? Does it affect functionality?

[yoshi-qc]

I discuss this issue with @sjdilkes . He manages this issue now.

[CalMacCQ]

Related to #415

[cqc-alec]

Closing as duplicate. I've made some of the changes necessary on a branch (see 1929e60 ) but it can't be merged because it causes test failures due to qiskit not having caught up yet.