Add clifford gates to collect_cliffords (#12750)

* add clifford gates to collect_cliffords

* replace hard coded clifford names by clifford_circuit names

* move import

* replace hard coded clifford names in random_clifford_circuit

* add release notes

* add permutation to collect_clifford gate list

(cherry picked from commit 41267ec)

# Conflicts:
#	qiskit/circuit/random/utils.py

qiskit/circuit/random/utils.py

@@ -18,6 +18,7 @@
 from qiskit.circuit import Reset
 from qiskit.circuit.library import standard_gates
 from qiskit.circuit.exceptions import CircuitError
+from qiskit.quantum_info.operators.symplectic.clifford_circuits import _BASIS_1Q, _BASIS_2Q
 
 
 def random_circuit(
@@ -207,3 +208,76 @@ def random_circuit(
         qc.measure(qc.qubits, cr)
 
     return qc
+<<<<<<< HEAD
+=======
+
+
+def random_clifford_circuit(num_qubits, num_gates, gates="all", seed=None):
+    """Generate a pseudo-random Clifford circuit.
+
+    This function will generate a Clifford circuit by randomly selecting the chosen amount of Clifford
+    gates from the set of standard gates in :mod:`qiskit.circuit.library.standard_gates`. For example:
+
+    .. plot::
+       :include-source:
+
+       from qiskit.circuit.random import random_clifford_circuit
+
+       circ = random_clifford_circuit(num_qubits=2, num_gates=6)
+       circ.draw(output='mpl')
+
+    Args:
+        num_qubits (int): number of quantum wires.
+        num_gates (int): number of gates in the circuit.
+        gates (list[str]): optional list of Clifford gate names to randomly sample from.
+            If ``"all"`` (default), use all Clifford gates in the standard library.
+        seed (int | np.random.Generator): sets random seed/generator (optional).
+
+    Returns:
+        QuantumCircuit: constructed circuit
+    """
+
+    gates_1q = list(set(_BASIS_1Q.keys()) - {"v", "w", "id", "iden", "sinv"})
+    gates_2q = list(_BASIS_2Q.keys())
+
+    if gates == "all":
+        if num_qubits == 1:
+            gates = gates_1q
+        else:
+            gates = gates_1q + gates_2q
+
+    instructions = {
+        "i": (standard_gates.IGate(), 1),
+        "x": (standard_gates.XGate(), 1),
+        "y": (standard_gates.YGate(), 1),
+        "z": (standard_gates.ZGate(), 1),
+        "h": (standard_gates.HGate(), 1),
+        "s": (standard_gates.SGate(), 1),
+        "sdg": (standard_gates.SdgGate(), 1),
+        "sx": (standard_gates.SXGate(), 1),
+        "sxdg": (standard_gates.SXdgGate(), 1),
+        "cx": (standard_gates.CXGate(), 2),
+        "cy": (standard_gates.CYGate(), 2),
+        "cz": (standard_gates.CZGate(), 2),
+        "swap": (standard_gates.SwapGate(), 2),
+        "iswap": (standard_gates.iSwapGate(), 2),
+        "ecr": (standard_gates.ECRGate(), 2),
+        "dcx": (standard_gates.DCXGate(), 2),
+    }
+
+    if isinstance(seed, np.random.Generator):
+        rng = seed
+    else:
+        rng = np.random.default_rng(seed)
+
+    samples = rng.choice(gates, num_gates)
+
+    circ = QuantumCircuit(num_qubits)
+
+    for name in samples:
+        gate, nqargs = instructions[name]
+        qargs = rng.choice(range(num_qubits), nqargs, replace=False).tolist()
+        circ.append(gate, qargs, copy=False)
+
+    return circ
+>>>>>>> 41267ecf5 (Add clifford gates to collect_cliffords (#12750))

qiskit/transpiler/passes/optimization/collect_cliffords.py

@@ -22,6 +22,7 @@
 )
 
 from qiskit.quantum_info.operators import Clifford
+from qiskit.quantum_info.operators.symplectic.clifford_circuits import _BASIS_1Q, _BASIS_2Q
 
 
 class CollectCliffords(CollectAndCollapse):
@@ -69,21 +70,11 @@ def __init__(
         )
 
 
-clifford_gate_names = [
-    "x",
-    "y",
-    "z",
-    "h",
-    "s",
-    "sdg",
-    "cx",
-    "cy",
-    "cz",
-    "swap",
-    "clifford",
-    "linear_function",
-    "pauli",
-]
+clifford_gate_names = (
+    list(_BASIS_1Q.keys())
+    + list(_BASIS_2Q.keys())
+    + ["clifford", "linear_function", "pauli", "permutation"]
+)
 
 
 def _is_clifford_gate(node):

releasenotes/notes/fix-collect-clifford-83af26d98b8c69e8.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Add more Clifford gates to the :class:`.CollectCliffords()` transpiler pass.
+    In particular, we have added the gates :class:`ECRGate()`, :class:`DCXGate()`,
+    :class:`iSWAPGate()`, :class:`SXGate()` and :class:`SXdgGate()` to this transpiler pass.