From 92bf92678d6c385923f8caee6b44473369e8610b Mon Sep 17 00:00:00 2001
From: "Kevin J. Sung" <kevjsung@umich.edu>
Date: Tue, 8 Nov 2022 07:50:45 -0500
Subject: [PATCH] add qubits and clbits args to
 QuantumCircuit.from_instructions (#9089)

* add qubits and clbits args to QuantumCircuit.from_instructions

* test classical bits too

* handle iterable correctly
---
 qiskit/circuit/quantumcircuit.py              | 14 +++++++++
 .../python/circuit/test_circuit_operations.py | 31 +++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/qiskit/circuit/quantumcircuit.py b/qiskit/circuit/quantumcircuit.py
index e982a8046c35..5c1f4134a90b 100644
--- a/qiskit/circuit/quantumcircuit.py
+++ b/qiskit/circuit/quantumcircuit.py
@@ -294,6 +294,8 @@ def from_instructions(
             | tuple[qiskit.circuit.Instruction, Iterable[Qubit], Iterable[Clbit]]
         ],
         *,
+        qubits: Iterable[Qubit] = (),
+        clbits: Iterable[Clbit] = (),
         name: Optional[str] = None,
         global_phase: ParameterValueType = 0,
         metadata: Optional[dict] = None,
@@ -302,6 +304,10 @@ def from_instructions(
 
         Args:
             instructions: The instructions to add to the circuit.
+            qubits: Any qubits to add to the circuit. This argument can be used,
+                for example, to enforce a particular ordering of qubits.
+            clbits: Any classical bits to add to the circuit. This argument can be used,
+                for example, to enforce a particular ordering of classical bits.
             name: The name of the circuit.
             global_phase: The global phase of the circuit in radians.
             metadata: Arbitrary key value metadata to associate with the circuit.
@@ -312,6 +318,14 @@ def from_instructions(
         circuit = QuantumCircuit(name=name, global_phase=global_phase, metadata=metadata)
         added_qubits = set()
         added_clbits = set()
+        if qubits:
+            qubits = list(qubits)
+            circuit.add_bits(qubits)
+            added_qubits.update(qubits)
+        if clbits:
+            clbits = list(clbits)
+            circuit.add_bits(clbits)
+            added_clbits.update(clbits)
         for instruction in instructions:
             if not isinstance(instruction, CircuitInstruction):
                 instruction = CircuitInstruction(*instruction)
diff --git a/test/python/circuit/test_circuit_operations.py b/test/python/circuit/test_circuit_operations.py
index 4b36555023fb..8b956482f3af 100644
--- a/test/python/circuit/test_circuit_operations.py
+++ b/test/python/circuit/test_circuit_operations.py
@@ -1187,6 +1187,37 @@ def instruction_tuples_partial():
         self.assertEqual(circuit_tuples, expected)
         self.assertEqual(circuit_tuples_partial, expected)
 
+    def test_from_instructions_bit_order(self):
+        """Test from_instructions method bit order."""
+        qreg = QuantumRegister(2)
+        creg = ClassicalRegister(2)
+        a, b = qreg
+        c, d = creg
+
+        def instructions():
+            yield CircuitInstruction(HGate(), [b], [])
+            yield CircuitInstruction(CXGate(), [a, b], [])
+            yield CircuitInstruction(Measure(), [b], [d])
+            yield CircuitInstruction(Measure(), [a], [c])
+
+        circuit = QuantumCircuit.from_instructions(instructions())
+        self.assertEqual(circuit.qubits, [b, a])
+        self.assertEqual(circuit.clbits, [d, c])
+
+        circuit = QuantumCircuit.from_instructions(instructions(), qubits=qreg)
+        self.assertEqual(circuit.qubits, [a, b])
+        self.assertEqual(circuit.clbits, [d, c])
+
+        circuit = QuantumCircuit.from_instructions(instructions(), clbits=creg)
+        self.assertEqual(circuit.qubits, [b, a])
+        self.assertEqual(circuit.clbits, [c, d])
+
+        circuit = QuantumCircuit.from_instructions(
+            instructions(), qubits=iter([a, b]), clbits=[c, d]
+        )
+        self.assertEqual(circuit.qubits, [a, b])
+        self.assertEqual(circuit.clbits, [c, d])
+
     def test_from_instructions_metadata(self):
         """Test from_instructions method passes metadata."""
         qreg = QuantumRegister(2)