Relax wire_order restrictions in circuit visualization

qiskit/opflow/__init__.py

@@ -19,7 +19,7 @@
 
 Operators and State functions are the building blocks of Quantum Algorithms.
 
-A library for Quantum Algorithms & Applications is more than a collection of
+A library for Quantum Algorithms & Applications (QA&A) is more than a collection of
 algorithms wrapped in Python functions. It needs to provide tools to make writing
 algorithms simple and easy. This is the layer of modules between the circuits and algorithms,
 providing the language and computational primitives for QA&A research.

qiskit/visualization/circuit/circuit_visualization.py

@@ -204,27 +204,42 @@ def circuit_drawer(
         raise VisualizationError(
             "The wire_order option cannot be set when the reverse_bits option is True."
         )
-    if wire_order is not None and len(wire_order) != circuit.num_qubits + circuit.num_clbits:
-        raise VisualizationError(
-            "The wire_order list must be the same "
-            "length as the sum of the number of qubits and clbits in the circuit."
-        )
-    if wire_order is not None and set(wire_order) != set(
-        range(circuit.num_qubits + circuit.num_clbits)
-    ):
-        raise VisualizationError(
-            "There must be one and only one entry in the "
-            "wire_order list for the index of each qubit and each clbit in the circuit."
-        )
+    complete_wire_order = None
+    if wire_order is not None:
+        if set(wire_order) > set(range(circuit.num_qubits + circuit.num_clbits)):
+            raise VisualizationError(
+                "The wire_order list should be a subset of the index for each qubit "
+                "and each clbit in the circuit."
+            )
+
+        if len(set(wire_order)) != len(wire_order):
+            raise VisualizationError(
+                "There must be one and only one entry in the "
+                "wire_order list for the index of each qubit and each clbit in the circuit."
+            )
+
+        if len(set(wire_order)) != len(wire_order):
+            raise VisualizationError("The wire_order list should not have repeated elements.")
+
+        rest_of_wires = list(range(circuit.num_qubits + circuit.num_clbits))
+        for wire in set(wire_order):
+            rest_of_wires.remove(wire)
+        complete_wire_order = wire_order + rest_of_wires
 
-    if circuit.clbits and (reverse_bits or wire_order is not None):
+    if (
+        circuit.clbits
+        and (reverse_bits or wire_order is not None)
+        and not set(wire_order or []).issubset(set(range(circuit.num_qubits)))
+    ):
         if cregbundle:
             warn(
-                "cregbundle set to False since either reverse_bits or wire_order has been set.",
+                "cregbundle set to False since either reverse_bits or wire_order "
+                "(over classical bit) has been set.",
                 RuntimeWarning,
                 2,
             )
         cregbundle = False
+
     if output == "text":
         return _text_circuit_drawer(
             circuit,
@@ -238,7 +253,7 @@ def circuit_drawer(
             fold=fold,
             initial_state=initial_state,
             cregbundle=cregbundle,
-            wire_order=wire_order,
+            wire_order=complete_wire_order,
         )
     elif output == "latex":
         image = _latex_circuit_drawer(
@@ -253,7 +268,7 @@ def circuit_drawer(
             with_layout=with_layout,
             initial_state=initial_state,
             cregbundle=cregbundle,
-            wire_order=wire_order,
+            wire_order=complete_wire_order,
         )
     elif output == "latex_source":
         return _generate_latex_source(
@@ -268,7 +283,7 @@ def circuit_drawer(
             with_layout=with_layout,
             initial_state=initial_state,
             cregbundle=cregbundle,
-            wire_order=wire_order,
+            wire_order=complete_wire_order,
         )
     elif output == "mpl":
         image = _matplotlib_circuit_drawer(
@@ -285,7 +300,7 @@ def circuit_drawer(
             ax=ax,
             initial_state=initial_state,
             cregbundle=cregbundle,
-            wire_order=wire_order,
+            wire_order=complete_wire_order,
         )
     else:
         raise VisualizationError(

releasenotes/notes/relax_wire_order_restrictions-ffc0cfeacd7b8d4b.yaml

@@ -0,0 +1,34 @@
+---
+features:
+  - |
+    Some restrictions when using ``wire_order`` in the circuit drawers had been relaxed.
+    Now, ``wire_order`` does not need to be a complete list and it can be used
+    with ``cregbundle=True`` when the order is not affecting the classical bits.
+
+    .. code-block::
+
+      from qiskit import QuantumCircuit, QuantumRegister, ClassicalRegister
+
+      qr = QuantumRegister(4, "q")
+      cr = ClassicalRegister(4, "c")
+      cr2 = ClassicalRegister(2, "ca")
+      circuit = QuantumCircuit(qr, cr, cr2)
+      circuit.h(0)
+      circuit.h(3)
+      circuit.x(1)
+      circuit.x(3).c_if(cr, 10)
+      circuit.draw('text', wire_order=[2, 3], cregbundle=True)
+
+    .. parsed-literal::
+
+       q_2: ────────────
+            ┌───┐ ┌───┐
+       q_3: ┤ H ├─┤ X ├─
+            ├───┤ └─╥─┘
+       q_0: ┤ H ├───╫───
+            ├───┤   ║
+       q_1: ┤ X ├───╫───
+            └───┘┌──╨──┐
+       c: 4/═════╡ 0xa ╞
+                 └─────┘
+      ca: 2/════════════

test/python/visualization/references/test_latex_wire_order_partial.tex

@@ -0,0 +1,20 @@
+\documentclass[border=2px]{standalone}
+
+\usepackage[braket, qm]{qcircuit}
+\usepackage{graphicx}
+
+\begin{document}
+\scalebox{1.0}{
+\Qcircuit @C=1.0em @R=0.2em @!R { \\
+	 	\nghost{{q}_{2} :  } & \lstick{{q}_{2} :  } & \qw & \qw & \qw & \qw\\
+	 	\nghost{{q}_{1} :  } & \lstick{{q}_{1} :  } & \gate{\mathrm{X}} & \qw & \qw & \qw\\
+	 	\nghost{{q}_{0} :  } & \lstick{{q}_{0} :  } & \gate{\mathrm{H}} & \qw & \qw & \qw\\
+	 	\nghost{{q}_{3} :  } & \lstick{{q}_{3} :  } & \gate{\mathrm{H}} & \gate{\mathrm{X}} & \qw & \qw\\
+	 	\nghost{{c}_{0} :  } & \lstick{{c}_{0} :  } & \cw & \controlo \cw \cwx[-1] & \cw & \cw\\
+	 	\nghost{{c}_{1} :  } & \lstick{{c}_{1} :  } & \cw & \controlo \cw \cwx[-1] & \cw & \cw\\
+	 	\nghost{{c}_{2} :  } & \lstick{{c}_{2} :  } & \cw & \control \cw \cwx[-1] & \cw & \cw\\
+	 	\nghost{{c}_{3} :  } & \lstick{{c}_{3} :  } & \cw & \control \cw^(0.0){^{\mathtt{0xc}}} \cwx[-1] & \cw & \cw\\
+	 	\nghost{{ca}_{0} :  } & \lstick{{ca}_{0} :  } & \cw & \cw & \cw & \cw\\
+	 	\nghost{{ca}_{1} :  } & \lstick{{ca}_{1} :  } & \cw & \cw & \cw & \cw\\
+\\ }}
+\end{document}

test/python/visualization/test_circuit_drawer.py

@@ -108,8 +108,6 @@ def test_wire_order_raises(self):
 
         circuit = QuantumCircuit(3, 3)
         circuit.x(1)
-        with self.assertRaisesRegex(VisualizationError, "the same length as"):
-            visualization.circuit_drawer(circuit, wire_order=[0, 1, 2])
 
         with self.assertRaisesRegex(VisualizationError, "one and only one entry"):
             visualization.circuit_drawer(circuit, wire_order=[2, 1, 0, 3, 1, 5])

test/python/visualization/test_circuit_latex.py

@@ -699,6 +699,26 @@ def test_wire_order(self):
         )
         self.assertEqualToReference(filename)
 
+    def test_wire_order_partial(self):
+        """Test the wire_order partial list to latex drawer"""
+        filename = self._get_resource_path("test_latex_wire_order_partial.tex")
+        qr = QuantumRegister(4, "q")
+        cr = ClassicalRegister(4, "c")
+        cr2 = ClassicalRegister(2, "ca")
+        circuit = QuantumCircuit(qr, cr, cr2)
+        circuit.h(0)
+        circuit.h(3)
+        circuit.x(1)
+        circuit.x(3).c_if(cr, 12)
+        circuit_drawer(
+            circuit,
+            cregbundle=False,
+            wire_order=[2, 1],
+            filename=filename,
+            output="latex_source",
+        )
+        self.assertEqualToReference(filename)
+
 
 if __name__ == "__main__":
     unittest.main(verbosity=2)

test/python/visualization/test_circuit_text_drawer.py

@@ -341,6 +341,33 @@ def test_wire_order(self):
             str(_text_circuit_drawer(circuit, wire_order=[2, 1, 3, 0, 6, 8, 9, 5, 4, 7])), expected
         )
 
+    def test_wire_order_partial(self):
+        """Test the wire_order option with a smaller list"""
+        expected = "\n".join(
+            [
+                "                    ",
+                "q_2: |0>────────────",
+                "        ┌───┐       ",
+                "q_1: |0>┤ X ├───────",
+                "        ├───┤ ┌───┐ ",
+                "q_3: |0>┤ H ├─┤ X ├─",
+                "        ├───┤ └─╥─┘ ",
+                "q_0: |0>┤ H ├───╫───",
+                "        └───┘┌──╨──┐",
+                " c: 0 4/═════╡ 0xa ╞",
+                "             └─────┘",
+            ]
+        )
+        qr = QuantumRegister(4, "q")
+        cr = ClassicalRegister(4, "c")
+        cr2 = ClassicalRegister(2, "ca")
+        circuit = QuantumCircuit(qr, cr, cr2)
+        circuit.h(0)
+        circuit.h(3)
+        circuit.x(1)
+        circuit.x(3).c_if(cr, 10)
+        self.assertEqual(str(_text_circuit_drawer(circuit, wire_order=[2, 1, 3, 0, 6])), expected)
+
     def test_text_swap(self):
         """Swap drawing."""
         expected = "\n".join(