Text drawer support for controlled/conditional custom instruction

[1ucian0]

Based on the consensus in #3073, the text drawer should support controlled/conditional custom instructions

Considering the following custom instruction:

        ┌─────────────┐            
q_0: |0>┤1            ├            
        │             │            
q_1: |0>┤             ├            
        │ instruction │            
 c_0: 0 ╡             ╞            
        │             │            
 c_1: 0 ╡0            ╞            
        └─────────────┘

It would be possible to control on q_1 and have a classical condition c == 2 and the result should look like this:

               ┌─────────────┐     
q_0: |0>───────┤1            ├     
               │             │     
q_1: |0>───────■             ├     
               │ instruction │     
 c_0: 0 ═┬─────┤             ╞     
         │ = 2 │             │     
 c_1: 0 ═┴─────┤0            ╞     
               └─────────────┘     

[1ucian0]

Custom controlled instructions are not yet supported (waiting for #2862 ) On the conditional part, I think this is the code to test this situation (not fully sure, because I cannot visualize the result)

from qiskit.circuit import Gate, Parameter
qinst = QuantumRegister(1, 'q')
cinst = ClassicalRegister(1, 'c')

inst = QuantumCircuit(qinst, cinst, name='instruction').to_instruction()

qr = QuantumRegister(2, 'q')
cr = ClassicalRegister(2, 'c')
circuit = QuantumCircuit(qr, cr)
circuit.append(inst, [qr[0]], [cr[1]]).c_if(cr, 2)
circuit.draw(output='text')

[1ucian0]

Also, it seems like text drawer also have problems with the following configuration:

qr1 = QuantumRegister(1, 'qr')
cr1 = ClassicalRegister(1, 'cr')
qr2 = QuantumRegister(2, 'qr')
cr2 = ClassicalRegister(2, 'cr')

inst = QuantumCircuit(qr1, cr1, name='name').to_instruction()
circuit = QuantumCircuit(qr2, cr2)
circuit.append(inst, [qr2[0]], [cr2[1]])
print(circuit)

[mrvee-qC]

Update for Santa:elf:- QGoGP

✅ Issue still reproducible! Instruction object currently doesn't have an explicit custom control method and conditions with overlapping c_if and q_if drawings are not implemented yet as discussed and voted in Issue #3073. Second comment seems to be fixed but original drawer layout as mentioned by OP not yet implemented.

from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit
from qiskit.circuit import Gate, Parameter
qinst = QuantumRegister(1, 'q')
cinst = ClassicalRegister(1, 'c')

inst = QuantumCircuit(qinst, cinst, name='instruction').to_instruction()

qr = QuantumRegister(2, 'q')
cr = ClassicalRegister(2, 'c')
circuit = QuantumCircuit(qr, cr)
circuit.append(inst, [qr[0]], [cr[1]]).c_if(cr, 2)
circuit.draw(output='text')

Current Output -

     ┌──────────────┐
q_0: ┤0             ├
     │              │
q_1: ┤              ├
     │  instruction │
c_0: ╡              ╞
     │              │
c_1: ╡0             ╞
     └──────────────┘

Expected -

               ┌─────────────┐     
q_0: |0>───────┤1            ├     
               │             │     
q_1: |0>───────■             ├     
               │ instruction │     
c_0: 0 ══┬─────┤             ╞     
         │ = 2 │             │     
c_1: 0 ══┴─────┤0            ╞     
               └─────────────┘     

Will update comment/add more comments if cause is found/fixed!

Python version 3.9.7
qiskit-terra version: 0.19.1