plot_circuit_layout output unexpected with registerless circuits

[1ucian0]

What is the current behavior?

Consider the following backend:

from qiskit.visualization import plot_gate_map
from qiskit.test.mock import FakeManhattan

backend = FakeManhattan()
plot_gate_map(backend)

Let's create a circuit with a layout:

from qiskit import QuantumCircuit
from qiskit.visualization import plot_circuit_layout
from qiskit.transpiler import Layout

circuit = QuantumCircuit(15)
circuit._layout = Layout({ circuit.qubits[im_j]: cm_i for cm_i, im_j in [ (i,j) for i,j in enumerate(range(14, -1, -1)) ]})
plot_circuit_layout(circuit, backend)

The drawing is unexpected to me. The layout is non-trivial, for example:

circuit._layout[0]

Qubit(QuantumRegister(15, 'q'), 14)

What is the expected behavior?

I would expect 14 in the top corner, where the 0 appears.

Suggested solutions

This bug is probably related with the recently introduced registerless circuits.

[singhsanskar202]

I would like to work on this issue.

[javabster]

Hi @singhsanskar202 it looks like there is already a PR open for this issue, feel free to help review the existing PR or pick up another issue 😄

[singhsanskar202]

ok

[Quant02]

I'm new here. Can I work on this one? I see no PR's for this or Is this issue solved?

[javabster]

I'm new here. Can I work on this one? I see no PR's for this or Is this issue solved?

Hi @Quant02 it looks like someone is already working on this and has opened a PR already. Please choose another issue to work on or reach out to the the first contributor to see if you can work with them or take over the issue if they are no longer up for it 😄

[1ucian0]

The PR #6648 was not having a lot of movement. @singhsanskar202 or @Quant02, does any of you would like to take over? If you use the code in #6648, remember to co-author it.

[ssawarn]

I would like to work on it.

[javabster]

Assigned to you @stoicodin, let us know if you have any questions and remember to co-author if you use the code in #6648 😄

[HuangJunye]

@stoicodin Hey, just want to check in to see if you are still working on this issue. Please let us know if you need any help!

[ssawarn]

I need help. As soon as I get free i will reach out and resolve.

On 18-Aug-2022, at 15:47, Junye Huang @.***> wrote:



@stoicodinhttps://github.com/stoicodin Hey, just want to check in to see if you are still working on this issue. Please let us know if you need any help!

— Reply to this email directly, view it on GitHubhttps://github.com/Qiskit/qiskit-terra/issues/6616#issuecomment-1219311211, or unsubscribehttps://github.com/notifications/unsubscribe-auth/AU2SB57323TQZBA4CPMRVULVZYEUTANCNFSM47BYCOHQ. You are receiving this because you were mentioned.Message ID: @.***>

[1ucian0]

Hi @stoicodin, shall we return this issue to the unassigned pool?

[ssawarn]

yes sir

[lmpawan10]

Hi, this is my first time here. I would like to work on the issue.

[javabster]

sure thing @lmpawan10 I'll assign to you 😄

As it is your first time here please remember to read the contributing guide. You may also find this youtube series useful for github tips as well

[border-b]

Hi @javabster, is this issue still open? If so, I would like to work in it as my first issue.

[border-b]

I tried to reproduce the issue and got the following error:

AttributeError: 'Layout' object has no attribute 'initial_layout'

It seems to be caused by the following code in gate_map.py

bit_locations = {
        bit: {"register": register, "index": index}
        for register in circuit._layout.initial_layout.get_registers()
        for index, bit in enumerate(register)
    }
    for index, qubit in enumerate(circuit._layout.initial_layout.get_virtual_bits()):
        if qubit not in bit_locations:
            bit_locations[qubit] = {"register": None, "index": index}

    if view == "virtual":
        for key, val in circuit._layout.initial_layout.get_virtual_bits().items():
            bit_register = bit_locations[key]["register"]
            if bit_register is None or bit_register.name != "ancilla":
                qubits.append(val)
                qubit_labels[val] = str(bit_locations[key]["index"])

    elif view == "physical":
        for key, val in circuit._layout.initial_layout.get_physical_bits().items():
            bit_register = bit_locations[val]["register"]
            if bit_register is None or bit_register.name != "ancilla":
                qubits.append(key)
                qubit_labels[key] = str(key)

Removing the initial_layout from this file reproduces the scenario that is described here. But the error persists when trying to use print(circuit). There is probably something wrong with the layout.py file where the initial_layout attribute is not properly defined.