Merge pull request #74 from kevinsung/crzz-decomp

add crzz decomposition

qiskit_research/utils/gate_decompositions.py

@@ -17,14 +17,15 @@
 from collections.abc import Iterator
 
 from qiskit import QuantumRegister
-from qiskit.circuit import Gate, Qubit
+from qiskit.circuit import ControlledGate, Gate, Qubit
 from qiskit.circuit.library import (
+    CXGate,
     HGate,
-    SGate,
-    SdgGate,
     RXGate,
     RZGate,
     RZXGate,
+    SdgGate,
+    SGate,
     XGate,
     XXMinusYYGate,
     XXPlusYYGate,
@@ -122,6 +123,39 @@ def run(
         return dag
 
 
+class ControlledRZZToCX(TransformationPass):
+    """Transformation pass to decompose Controlled RZZGate to CXGate."""
+
+    def _decomposition(
+        self,
+        register: QuantumRegister,
+        gate: ControlledGate,
+    ) -> Iterator[tuple[Gate, tuple[Qubit, ...]]]:
+        a, b, c = register
+        (theta,) = gate.params
+
+        yield CXGate(), (b, c)
+        yield RZGate(theta).control(1), (a, c)
+        yield CXGate(), (b, c)
+
+    def run(
+        self,
+        dag: DAGCircuit,
+    ) -> DAGCircuit:
+        for run in dag.collect_runs(["crzz"]):
+            for node in run:
+                mini_dag = DAGCircuit()
+                register = QuantumRegister(3)
+                mini_dag.add_qreg(register)
+
+                for instr, qargs in self._decomposition(register, node.op):
+                    mini_dag.apply_operation_back(instr, qargs)
+
+                dag.substitute_node_with_dag(node, mini_dag)
+
+        return dag
+
+
 class XXPlusYYtoRZX(TransformationPass):
     """Transformation pass to decompose XXPlusYYGate to RZXGate."""
 

test/utils/test_gate_decompositions.py

@@ -16,10 +16,12 @@
 
 import numpy as np
 from qiskit.circuit import QuantumCircuit, QuantumRegister
-from qiskit.circuit.library import XXMinusYYGate, XXPlusYYGate
-from qiskit.transpiler import PassManager
+from qiskit.circuit.library import RZZGate, XXMinusYYGate, XXPlusYYGate
 from qiskit.quantum_info import Operator
+from qiskit.transpiler import PassManager
+
 from qiskit_research.utils.gate_decompositions import (
+    ControlledRZZToCX,
     RZXWeylDecomposition,
     XXMinusYYtoRZX,
     XXPlusYYtoRZX,
@@ -29,10 +31,24 @@
 class TestPasses(unittest.TestCase):
     """Test passes."""
 
+    def test_controlled_rzz_to_cx(self):
+        """Test controlled RZZGate to CXGate decomposition."""
+        rng = np.random.default_rng()
+        theta = rng.uniform(-10, 10)
+        gate = RZZGate(theta).control(1)
+        register = QuantumRegister(3)
+        circuit = QuantumCircuit(register)
+        circuit.append(gate, register)
+        pass_ = ControlledRZZToCX()
+        pass_manager = PassManager([pass_])
+        decomposed = pass_manager.run(circuit)
+        self.assertTrue(Operator(circuit).equiv(Operator(decomposed)))
+
     def test_xxplusyy_to_rzx(self):
         """Test XXPlusYYGate to RZXGate decomposition."""
-        theta = np.random.uniform(-10, 10)
-        beta = np.random.uniform(-10, 10)
+        rng = np.random.default_rng()
+        theta = rng.uniform(-10, 10)
+        beta = rng.uniform(-10, 10)
         gate = XXPlusYYGate(theta, beta)
         register = QuantumRegister(2)
         circuit = QuantumCircuit(register)
@@ -44,8 +60,9 @@ def test_xxplusyy_to_rzx(self):
 
     def test_xxminusyy_to_rzx(self):
         """Test XXMinusYYGate to RZXGate decomposition."""
-        theta = np.random.uniform(-10, 10)
-        beta = np.random.uniform(-10, 10)
+        rng = np.random.default_rng()
+        theta = rng.uniform(-10, 10)
+        beta = rng.uniform(-10, 10)
         gate = XXMinusYYGate(theta, beta)
         register = QuantumRegister(2)
         circuit = QuantumCircuit(register)