From 3523aea7d38889ae8b508814e006ce8434b2673b Mon Sep 17 00:00:00 2001
From: Naoki Kanazawa <nkanazawa1989@gmail.com>
Date: Thu, 20 Jun 2024 22:01:56 +0900
Subject: [PATCH] Fix v2 pulse drawer  (#12608)
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* fix error when V2 model is set

* Apply suggestions from code review

* Fix black

---------

Co-authored-by: Elena Peña Tapia <57907331+ElePT@users.noreply.github.com>
Co-authored-by: Elena Peña Tapia <epenatap@gmail.com>
(cherry picked from commit 7d1731b60d8dd6219a292dc62f24d1a8d780e43a)
---
 qiskit/visualization/pulse_v2/device_info.py  | 89 ++++++++++++-------
 .../fix-v2-pulse-drawer-d05e4e392766909f.yaml |  7 ++
 2 files changed, 65 insertions(+), 31 deletions(-)
 create mode 100644 releasenotes/notes/fix-v2-pulse-drawer-d05e4e392766909f.yaml

diff --git a/qiskit/visualization/pulse_v2/device_info.py b/qiskit/visualization/pulse_v2/device_info.py
index 1e809c43abd2..7898f978772c 100644
--- a/qiskit/visualization/pulse_v2/device_info.py
+++ b/qiskit/visualization/pulse_v2/device_info.py
@@ -40,7 +40,7 @@ class :py:class:``DrawerBackendInfo`` with necessary methods to generate drawing
 
 from qiskit import pulse
 from qiskit.providers import BackendConfigurationError
-from qiskit.providers.backend import Backend
+from qiskit.providers.backend import Backend, BackendV2
 
 
 class DrawerBackendInfo(ABC):
@@ -106,40 +106,67 @@ def create_from_backend(cls, backend: Backend):
         Returns:
             OpenPulseBackendInfo: New configured instance.
         """
-        configuration = backend.configuration()
-        defaults = backend.defaults()
-
-        # load name
-        name = backend.name()
-
-        # load cycle time
-        dt = configuration.dt
-
-        # load frequencies
         chan_freqs = {}
-
-        chan_freqs.update(
-            {pulse.DriveChannel(qind): freq for qind, freq in enumerate(defaults.qubit_freq_est)}
-        )
-        chan_freqs.update(
-            {pulse.MeasureChannel(qind): freq for qind, freq in enumerate(defaults.meas_freq_est)}
-        )
-        for qind, u_lo_mappers in enumerate(configuration.u_channel_lo):
-            temp_val = 0.0 + 0.0j
-            for u_lo_mapper in u_lo_mappers:
-                temp_val += defaults.qubit_freq_est[u_lo_mapper.q] * u_lo_mapper.scale
-            chan_freqs[pulse.ControlChannel(qind)] = temp_val.real
-
-        # load qubit channel mapping
         qubit_channel_map = defaultdict(list)
-        for qind in range(configuration.n_qubits):
-            qubit_channel_map[qind].append(configuration.drive(qubit=qind))
-            qubit_channel_map[qind].append(configuration.measure(qubit=qind))
-            for tind in range(configuration.n_qubits):
+
+        if hasattr(backend, "configuration") and hasattr(backend, "defaults"):
+            configuration = backend.configuration()
+            defaults = backend.defaults()
+
+            name = configuration.backend_name
+            dt = configuration.dt
+
+            # load frequencies
+            chan_freqs.update(
+                {
+                    pulse.DriveChannel(qind): freq
+                    for qind, freq in enumerate(defaults.qubit_freq_est)
+                }
+            )
+            chan_freqs.update(
+                {
+                    pulse.MeasureChannel(qind): freq
+                    for qind, freq in enumerate(defaults.meas_freq_est)
+                }
+            )
+            for qind, u_lo_mappers in enumerate(configuration.u_channel_lo):
+                temp_val = 0.0 + 0.0j
+                for u_lo_mapper in u_lo_mappers:
+                    temp_val += defaults.qubit_freq_est[u_lo_mapper.q] * u_lo_mapper.scale
+                chan_freqs[pulse.ControlChannel(qind)] = temp_val.real
+
+            # load qubit channel mapping
+            for qind in range(configuration.n_qubits):
+                qubit_channel_map[qind].append(configuration.drive(qubit=qind))
+                qubit_channel_map[qind].append(configuration.measure(qubit=qind))
+                for tind in range(configuration.n_qubits):
+                    try:
+                        qubit_channel_map[qind].extend(configuration.control(qubits=(qind, tind)))
+                    except BackendConfigurationError:
+                        pass
+        elif isinstance(backend, BackendV2):
+            # Pure V2 model doesn't contain channel frequency information.
+            name = backend.name
+            dt = backend.dt
+
+            # load qubit channel mapping
+            for qind in range(backend.num_qubits):
+                # channels are NotImplemented by default so we must catch arbitrary error.
+                try:
+                    qubit_channel_map[qind].append(backend.drive_channel(qind))
+                except Exception:  # pylint: disable=broad-except
+                    pass
                 try:
-                    qubit_channel_map[qind].extend(configuration.control(qubits=(qind, tind)))
-                except BackendConfigurationError:
+                    qubit_channel_map[qind].append(backend.measure_channel(qind))
+                except Exception:  # pylint: disable=broad-except
                     pass
+                for tind in range(backend.num_qubits):
+                    try:
+                        qubit_channel_map[qind].extend(backend.control_channel(qubits=(qind, tind)))
+                    except Exception:  # pylint: disable=broad-except
+                        pass
+        else:
+            raise RuntimeError("Backend object not yet supported")
 
         return OpenPulseBackendInfo(
             name=name, dt=dt, channel_frequency_map=chan_freqs, qubit_channel_map=qubit_channel_map
diff --git a/releasenotes/notes/fix-v2-pulse-drawer-d05e4e392766909f.yaml b/releasenotes/notes/fix-v2-pulse-drawer-d05e4e392766909f.yaml
new file mode 100644
index 000000000000..b158703c6b89
--- /dev/null
+++ b/releasenotes/notes/fix-v2-pulse-drawer-d05e4e392766909f.yaml
@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    Fixed a bug in :func:`qiskit.visualization.pulse_v2.interface.draw` that didn't 
+    draw pulse schedules when the draw function was called with a :class:`.BackendV2` argument.
+    Because the V2 backend doesn't report hardware channel frequencies,
+    the generated drawing will show 'no freq.' below each channel label.