Merge pull request #1257 from qiboteam/clifford-check

Update `gate.clifford` value in rotations given a new angle

src/qibo/gates/abstract.py

@@ -46,7 +46,6 @@ def __init__(self):
         self.init_args = []
         self.init_kwargs = {}
 
-        self.clifford = False
         self.unitary = False
         self._target_qubits = ()
         self._control_qubits = ()
@@ -59,6 +58,11 @@ def __init__(self):
         self.device_gates = set()
         self.original_gate = None
 
+    @property
+    def clifford(self):
+        """Return boolean value representing if a Gate is Clifford or not."""
+        return False
+
     @property
     def raw(self) -> dict:
         """Serialize to dictionary.

src/qibo/gates/gates.py

@@ -29,9 +29,12 @@ def __init__(self, q):
         self.draw_label = "H"
         self.target_qubits = (q,)
         self.init_args = [q]
-        self.clifford = True
         self.unitary = True
 
+    @property
+    def clifford(self):
+        return True
+
     @property
     def qasm_label(self):
         return "h"
@@ -58,9 +61,12 @@ def __init__(self, q):
         self.draw_label = "X"
         self.target_qubits = (q,)
         self.init_args = [q]
-        self.clifford = True
         self.unitary = True
 
+    @property
+    def clifford(self):
+        return True
+
     @property
     def qasm_label(self):
         return "x"
@@ -171,9 +177,12 @@ def __init__(self, q):
         self.draw_label = "Y"
         self.target_qubits = (q,)
         self.init_args = [q]
-        self.clifford = True
         self.unitary = True
 
+    @property
+    def clifford(self):
+        return True
+
     @property
     def qasm_label(self):
         return "y"
@@ -215,9 +224,12 @@ def __init__(self, q):
         self.draw_label = "Z"
         self.target_qubits = (q,)
         self.init_args = [q]
-        self.clifford = True
         self.unitary = True
 
+    @property
+    def clifford(self):
+        return True
+
     @property
     def qasm_label(self):
         return "z"
@@ -256,9 +268,12 @@ def __init__(self, q):
         self.draw_label = "SX"
         self.target_qubits = (q,)
         self.init_args = [q]
-        self.clifford = True
         self.unitary = True
 
+    @property
+    def clifford(self):
+        return True
+
     @property
     def qasm_label(self):
         return "sx"
@@ -303,9 +318,12 @@ def __init__(self, q):
         self.draw_label = "SXDG"
         self.target_qubits = (q,)
         self.init_args = [q]
-        self.clifford = True
         self.unitary = True
 
+    @property
+    def clifford(self):
+        return True
+
     @property
     def qasm_label(self):
         return "sxdg"
@@ -350,9 +368,12 @@ def __init__(self, q):
         self.draw_label = "S"
         self.target_qubits = (q,)
         self.init_args = [q]
-        self.clifford = True
         self.unitary = True
 
+    @property
+    def clifford(self):
+        return True
+
     @property
     def qasm_label(self):
         return "s"
@@ -382,9 +403,12 @@ def __init__(self, q):
         self.draw_label = "SDG"
         self.target_qubits = (q,)
         self.init_args = [q]
-        self.clifford = True
         self.unitary = True
 
+    @property
+    def clifford(self):
+        return True
+
     @property
     def qasm_label(self):
         return "sdg"
@@ -468,9 +492,12 @@ def __init__(self, *q):
         self.draw_label = "I"
         self.target_qubits = tuple(q)
         self.init_args = q
-        self.clifford = True
         self.unitary = True
 
+    @property
+    def clifford(self):
+        return True
+
     @property
     def qasm_label(self):
         return "id"
@@ -502,6 +529,11 @@ def __init__(self, *q, delay: int = 0):
         self.target_qubits = tuple(q)
 
 
+def _is_clifford_given_angle(angle):
+    """Helper function to update Clifford boolean condition according to the given angle ``angle``."""
+    return isinstance(angle, (float, int)) and (angle % (np.pi / 2)).is_integer()
+
+
 class _Rn_(ParametrizedGate):
     """Abstract class for defining the RX, RY and RZ rotations.
 
@@ -524,13 +556,14 @@ def __init__(self, q, theta, trainable=True):
         if isinstance(theta, Parameter):
             theta = theta()
 
-        if isinstance(theta, (float, int)) and (theta % (np.pi / 2)).is_integer():
-            self.clifford = True
-
         self.parameters = theta
         self.init_args = [q]
         self.init_kwargs = {"theta": theta, "trainable": trainable}
 
+    @property
+    def clifford(self):
+        return _is_clifford_given_angle(self.parameters[0])
+
     def _dagger(self) -> "Gate":
         """"""
         return self.__class__(
@@ -974,9 +1007,12 @@ def __init__(self, q0, q1):
         self.control_qubits = (q0,)
         self.target_qubits = (q1,)
         self.init_args = [q0, q1]
-        self.clifford = True
         self.unitary = True
 
+    @property
+    def clifford(self):
+        return True
+
     @property
     def qasm_label(self):
         return "cx"
@@ -1011,9 +1047,12 @@ def __init__(self, q0, q1):
         self.control_qubits = (q0,)
         self.target_qubits = (q1,)
         self.init_args = [q0, q1]
-        self.clifford = True
         self.unitary = True
 
+    @property
+    def clifford(self):
+        return True
+
     @property
     def qasm_label(self):
         return "cy"
@@ -1057,9 +1096,12 @@ def __init__(self, q0, q1):
         self.control_qubits = (q0,)
         self.target_qubits = (q1,)
         self.init_args = [q0, q1]
-        self.clifford = True
         self.unitary = True
 
+    @property
+    def clifford(self):
+        return True
+
     @property
     def qasm_label(self):
         return "cz"
@@ -1186,12 +1228,13 @@ def __init__(self, q0, q1, theta, trainable=True):
         self.parameters = theta
         self.unitary = True
 
-        if isinstance(theta, (float, int)) and (theta % np.pi).is_integer():
-            self.clifford = True
-
         self.init_args = [q0, q1]
         self.init_kwargs = {"theta": theta, "trainable": trainable}
 
+    @property
+    def clifford(self):
+        return _is_clifford_given_angle(self.parameters[0])
+
     def _dagger(self) -> "Gate":
         """"""
         q0 = self.control_qubits[0]
@@ -1484,9 +1527,12 @@ def __init__(self, q0, q1):
         self.draw_label = "x"
         self.target_qubits = (q0, q1)
         self.init_args = [q0, q1]
-        self.clifford = True
         self.unitary = True
 
+    @property
+    def clifford(self):
+        return True
+
     @property
     def qasm_label(self):
         return "swap"
@@ -1516,9 +1562,12 @@ def __init__(self, q0, q1):
         self.draw_label = "i"
         self.target_qubits = (q0, q1)
         self.init_args = [q0, q1]
-        self.clifford = True
         self.unitary = True
 
+    @property
+    def clifford(self):
+        return True
+
     @property
     def qasm_label(self):
         return "iswap"
@@ -1608,9 +1657,12 @@ def __init__(self, q0, q1):
         self.draw_label = "fx"
         self.target_qubits = (q0, q1)
         self.init_args = [q0, q1]
-        self.clifford = True
         self.unitary = True
 
+    @property
+    def clifford(self):
+        return True
+
     @property
     def qasm_label(self):
         return "fswap"
@@ -2158,9 +2210,12 @@ def __init__(self, q0, q1):
         self.draw_label = "ECR"
         self.target_qubits = (q0, q1)
         self.init_args = [q0, q1]
-        self.clifford = True
         self.unitary = True
 
+    @property
+    def clifford(self):
+        return True
+
     def decompose(self, *free, use_toffolis: bool = True) -> List[Gate]:
         """Decomposition of :math:`\\textup{ECR}` gate up to global phase.
 
@@ -2315,6 +2370,7 @@ def __init__(
         self.name = "Unitary" if name is None else name
         self.draw_label = "U"
         self.target_qubits = tuple(q)
+        self._clifford = False
 
         # TODO: Check that given ``unitary`` has proper shape?
         self.parameter_names = "u"
@@ -2361,6 +2417,14 @@ def parameters(self, x):
         for gate in self.device_gates:  # pragma: no cover
             gate.parameters = x
 
+    @property
+    def clifford(self):
+        return self._clifford
+
+    @clifford.setter
+    def clifford(self, value):
+        self._clifford = value
+
     def on_qubits(self, qubit_map):
         args = [self.init_args[0]]
         args.extend(qubit_map.get(i) for i in self.target_qubits)

src/qibo/models/error_mitigation.py

@@ -205,7 +205,7 @@ def sample_training_circuit_cdr(
     gates_to_replace = []
     for i, gate in enumerate(circuit.queue):
         if isinstance(gate, gates.RZ):
-            if gate.init_kwargs["theta"] % (np.pi / 2) != 0.0:
+            if not gate.clifford:
                 gates_to_replace.append((i, gate))
 
     if not gates_to_replace:

tests/test_gates_gates.py

@@ -686,7 +686,7 @@ def test_cun(backend, name, params):
 
     if name in ["CRX", "CRY", "CRZ"]:
         theta = params["theta"]
-        if (theta % np.pi).is_integer():
+        if (theta % (np.pi / 2)).is_integer():
             assert gate.clifford
         else:
             assert not gate.clifford
@@ -1689,3 +1689,28 @@ def test_x_decomposition_execution(backend, target, controls, free, use_toffolis
 
 
 ###############################################################################
+
+####################### Test Clifford updates #################################
+
+
+@pytest.mark.parametrize(
+    "gate",
+    [
+        gates.RX(0, 0),
+        gates.RY(0, 0),
+        gates.RZ(0, 0),
+        gates.CRX(0, 1, 0),
+        gates.CRY(0, 1, 0),
+        gates.CRZ(0, 1, 0),
+    ],
+)
+def test_clifford_condition_update(backend, gate):
+    """Test clifford condition update if setting new angle into the rotations."""
+    assert gate.clifford == True
+    gate.parameters = 0.5
+    assert gate.clifford == False
+    gate.parameters = np.pi
+    assert gate.clifford == True
+
+
+###############################################################################

tests/test_models_error_mitigation.py

@@ -215,8 +215,6 @@ def test_sample_training_circuit(nqubits):
     c.add(gates.CNOT(q, q + 1) for q in range(1, nqubits, 2))
     c.add(gates.M(q) for q in range(nqubits))
 
-    for j in range(len(c.queue)):
-        c.queue[j].clifford = True
     with pytest.raises(ValueError):
         sample_training_circuit_cdr(c)
     with pytest.raises(ValueError):