Add 2q fractional gates to the UnitarySynthesis tranpiler pass

qiskit/synthesis/two_qubit/two_qubit_decompose.py

@@ -290,7 +290,9 @@ def __init__(self, rxx_equivalent_gate: Type[Gate]):
         self.rxx_equivalent_gate = rxx_equivalent_gate
         self.scale = self._inner_decomposition.scale
 
-    def __call__(self, unitary: Operator | np.ndarray, *, atol=DEFAULT_ATOL) -> QuantumCircuit:
+    def __call__(
+        self, unitary: Operator | np.ndarray, approximate=False, use_dag=False, atol=DEFAULT_ATOL
+    ) -> QuantumCircuit:
         """Returns the Weyl decomposition in circuit form.
         Args:
             unitary (Operator or ndarray): :math:`4 \times 4` unitary to synthesize.

qiskit/transpiler/passes/synthesis/unitary_synthesis.py

@@ -38,6 +38,7 @@
     RXXGate,
     RZXGate,
     RZZGate,
+    RYYGate,
     ECRGate,
     RXGate,
     SXGate,
@@ -50,6 +51,10 @@
     U3Gate,
     RYGate,
     RGate,
+    CRXGate,
+    CRYGate,
+    CRZGate,
+    CPhaseGate,
 )
 from qiskit.converters import circuit_to_dag, dag_to_circuit
 from qiskit.dagcircuit.dagcircuit import DAGCircuit
@@ -62,6 +67,7 @@
 from qiskit.synthesis.two_qubit.two_qubit_decompose import (
     TwoQubitBasisDecomposer,
     TwoQubitWeylDecomposition,
+    TwoQubitControlledUDecomposer,
 )
 from qiskit.transpiler.basepasses import TransformationPass
 from qiskit.transpiler.coupling import CouplingMap
@@ -88,16 +94,32 @@
     "u3": U3Gate._standard_gate,
     "ry": RYGate._standard_gate,
     "r": RGate._standard_gate,
+    "rzz": RZZGate._standard_gate,
+    "ryy": RYYGate._standard_gate,
+    "rxx": RXXGate._standard_gate,
+    "rzx": RXXGate._standard_gate,
+    "cp": CPhaseGate._standard_gate,
+    "crx": RXXGate._standard_gate,
+    "cry": RXXGate._standard_gate,
+    "crz": RXXGate._standard_gate,
 }
 
+KAK_GATE_PARAM_NAMES = {
+    "rxx": RXXGate,
+    "rzz": RZZGate,
+    "ryy": RYYGate,
+    "rzx": RZXGate,
+    "cphase": CPhaseGate,
+    "crx": CRXGate,
+    "cry": CRYGate,
+    "crz": CRZGate,
+}
 
 KAK_GATE_NAMES = {
     "cx": CXGate(),
     "cz": CZGate(),
     "iswap": iSwapGate(),
-    "rxx": RXXGate(pi / 2),
     "ecr": ECRGate(),
-    "rzx": RZXGate(pi / 4),  # typically pi/6 is also available
 }
 
 GateNameToGate = get_standard_gate_name_mapping()
@@ -107,7 +129,12 @@ def _choose_kak_gate(basis_gates):
     """Choose the first available 2q gate to use in the KAK decomposition."""
     kak_gate = None
     kak_gates = set(basis_gates or []).intersection(KAK_GATE_NAMES.keys())
-    if kak_gates:
+    kak_gates_params = set(basis_gates or []).intersection(KAK_GATE_PARAM_NAMES.keys())
+
+    if kak_gates_params:
+        kak_gate = KAK_GATE_PARAM_NAMES[kak_gates_params.pop()]
+
+    elif kak_gates:
         kak_gate = KAK_GATE_NAMES[kak_gates.pop()]
 
     return kak_gate
@@ -151,14 +178,17 @@ def _decomposer_2q_from_basis_gates(basis_gates, pulse_optimize=None, approximat
     kak_gate = _choose_kak_gate(basis_gates)
     euler_basis = _choose_euler_basis(basis_gates)
     basis_fidelity = approximation_degree or 1.0
-    if isinstance(kak_gate, RZXGate):
-        backup_optimizer = TwoQubitBasisDecomposer(
-            CXGate(),
-            basis_fidelity=basis_fidelity,
-            euler_basis=euler_basis,
-            pulse_optimize=pulse_optimize,
-        )
-        decomposer2q = XXDecomposer(euler_basis=euler_basis, backup_optimizer=backup_optimizer)
+    # if isinstance(kak_gate, RZXGate):
+    #    backup_optimizer = TwoQubitBasisDecomposer(
+    #        CXGate(),
+    #        basis_fidelity=basis_fidelity,
+    #        euler_basis=euler_basis,
+    #        pulse_optimize=pulse_optimize,
+    #    )
+    #    decomposer2q = XXDecomposer(euler_basis=euler_basis, backup_optimizer=backup_optimizer)
+
+    if kak_gate in KAK_GATE_PARAM_NAMES.values():
+        decomposer2q = TwoQubitControlledUDecomposer(kak_gate)
     elif kak_gate is not None:
         decomposer2q = TwoQubitBasisDecomposer(
             kak_gate,

test/python/compiler/test_transpiler.py

@@ -1277,7 +1277,7 @@ def test_block_collection_reduces_1q_gate(self, basis_gates, gate_counts):
         basis_gates=[
             ["u3", "cx"],
             ["rx", "rz", "iswap"],
-            ["rx", "ry", "rxx"],
+            ["ry", "rz", "rxx"],
         ],
     )
     def test_translation_method_synthesis(self, optimization_level, basis_gates):

test/python/transpiler/test_unitary_synthesis.py

@@ -130,7 +130,8 @@ def test_empty_basis_gates(self):
     @data(
         ["u3", "cx"],
         ["u1", "u2", "u3", "cx"],
-        ["rx", "ry", "rxx"],
+        ["ry", "rz", "rxx"],
+        ["ry", "rz", "rzz"],
         ["rx", "rz", "iswap"],
         ["u3", "rx", "rz", "cz", "iswap"],
     )