Update plot_gate_map() family to leverage graphviz for visualization

releasenotes/notes/update-gate-map-visualizations-6ea907a0502fdc1a.yaml

@@ -0,0 +1,19 @@
+---
+features:
+  - |
+    The visualizations from the :func:`~.plot_gate_map`,  :func:`~.plot_coupling_map`.
+    :func:`~.plot_error_map`,  and :func:`~.plot_circuit_layout` functions have been significantly
+    improved for rendering layouts of backends with large numbers of qubits. This was accomplished
+    by leveraging `graphviz <https://graphviz.org/>`__ through rustworkx's ``graphviz_draw()`` function
+    to perform a more sophisticated algorithmic graph layout that scales for large numbers of
+    qubits.
+
+upgrade:
+  - |
+    The visualization functions: :func:`~.plot_gate_map`,  :func:`~.plot_coupling_map`.
+    :func:`~.plot_error_map`,  and :func:`~.plot_circuit_layout` now depend on
+    `graphviz <https://graphviz.org/>`__ being installed to function. This change was
+    necessary to enable visualizing backends with larger numbers of qubits. This
+    additional external requirement is in addition to the existing optional dependencies
+    these functions previously required. You find details on how to install
+    graphviz here:  https://graphviz.org/download/

test/python/visualization/test_gate_map.py

@@ -55,6 +55,8 @@ class TestGateMap(QiskitVisualizationTestCase):
     )
 
     @data(*backends)
+    @unittest.skipIf(not optionals.HAS_MATPLOTLIB, "matplotlib not available.")
+    @unittest.skipUnless(optionals.HAS_GRAPHVIZ, "Graphviz not installed")
     def test_plot_gate_map(self, backend):
         """tests plotting of gate map of a device (20 qubit, 16 qubit, 14 qubit and 5 qubit)"""
         n = backend.configuration().n_qubits
@@ -67,6 +69,8 @@ def test_plot_gate_map(self, backend):
         plt.close(fig)
 
     @data(*backends)
+    @unittest.skipIf(not optionals.HAS_MATPLOTLIB, "matplotlib not available.")
+    @unittest.skipUnless(optionals.HAS_GRAPHVIZ, "Graphviz not installed")
     def test_plot_circuit_layout(self, backend):
         """tests plot_circuit_layout for each device"""
         layout_length = int(backend._configuration.n_qubits / 2)
@@ -83,9 +87,11 @@ def test_plot_circuit_layout(self, backend):
         with BytesIO() as img_buffer:
             fig.savefig(img_buffer, format="png")
             img_buffer.seek(0)
-            self.assertImagesAreEqual(Image.open(img_buffer), img_ref, 0.1)
+            self.assertImagesAreEqual(Image.open(img_buffer), img_ref, 0.2)
         plt.close(fig)
 
+    @unittest.skipIf(not optionals.HAS_MATPLOTLIB, "matplotlib not available.")
+    @unittest.skipUnless(optionals.HAS_GRAPHVIZ, "Graphviz not installed")
     def test_plot_gate_map_no_backend(self):
         """tests plotting of gate map without a device"""
         n_qubits = 8
@@ -101,6 +107,9 @@ def test_plot_gate_map_no_backend(self):
             self.assertImagesAreEqual(Image.open(img_buffer), img_ref, 0.2)
         plt.close(fig)
 
+    @unittest.skipIf(not optionals.HAS_MATPLOTLIB, "matplotlib not available.")
+    @unittest.skipUnless(optionals.HAS_GRAPHVIZ, "Graphviz not installed")
+    @unittest.skipUnless(optionals.HAS_SEABORN, "Seaborn not installed")
     def test_plot_error_map_backend_v1(self):
         """Test plotting error map with fake backend v1."""
         backend = FakeKolkata()
@@ -112,6 +121,9 @@ def test_plot_error_map_backend_v1(self):
             self.assertImagesAreEqual(Image.open(img_buffer), img_ref, 0.2)
         plt.close(fig)
 
+    @unittest.skipIf(not optionals.HAS_MATPLOTLIB, "matplotlib not available.")
+    @unittest.skipUnless(optionals.HAS_GRAPHVIZ, "Graphviz not installed")
+    @unittest.skipUnless(optionals.HAS_SEABORN, "Seaborn not installed")
     def test_plot_error_map_backend_v2(self):
         """Test plotting error map with fake backend v2."""
         backend = FakeKolkataV2()
@@ -123,6 +135,9 @@ def test_plot_error_map_backend_v2(self):
             self.assertImagesAreEqual(Image.open(img_buffer), img_ref, 0.2)
         plt.close(fig)
 
+    @unittest.skipIf(not optionals.HAS_MATPLOTLIB, "matplotlib not available.")
+    @unittest.skipUnless(optionals.HAS_GRAPHVIZ, "Graphviz not installed")
+    @unittest.skipUnless(optionals.HAS_SEABORN, "Seaborn not installed")
     def test_plot_error_map_over_100_qubit(self):
         """Test plotting error map with large fake backend."""
         backend = FakeWashington()
@@ -134,6 +149,9 @@ def test_plot_error_map_over_100_qubit(self):
             self.assertImagesAreEqual(Image.open(img_buffer), img_ref, 0.2)
         plt.close(fig)
 
+    @unittest.skipIf(not optionals.HAS_MATPLOTLIB, "matplotlib not available.")
+    @unittest.skipUnless(optionals.HAS_GRAPHVIZ, "Graphviz not installed")
+    @unittest.skipUnless(optionals.HAS_SEABORN, "Seaborn not installed")
     def test_plot_error_map_over_100_qubit_backend_v2(self):
         """Test plotting error map with large fake backendv2."""
         backend = FakeWashingtonV2()