Add decomposition for CCZ gate and IonQTargetGateset when qubits are all-to-all connected

cirq-core/cirq/ops/three_qubit_gates.py

@@ -97,8 +97,15 @@ def _pauli_expansion_(self) -> value.LinearDict[str]:
             }
         )
 
-    def _decompose_(self, qubits):
-        """An adjacency-respecting decomposition.
+    def _decompose_(self, qubits, all_to_all_connect: Optional[bool] = None):
+        """If qubits are all-to-all connected, e.g. qubits in the same ion trap,
+        the decomposition will be:
+        0: ──────────────@──────────────────@───@───p──────@───
+                         │                  │   │          │
+        1: ───@──────────┼───────@───p──────┼───X───p^-1───X───
+              │          │       │          │
+        2: ───X───p^-1───X───p───X───p^-1───X───p──────────────
+        Otherwise the adjacency-respecting decomposition will be returned:
 
         0: ───p───@──────────────@───────@──────────@──────────
                   │              │       │          │
@@ -110,26 +117,44 @@ def _decompose_(self, qubits):
         """
         a, b, c = qubits
 
-        # Hacky magic: avoid the non-adjacent edge.
-        if hasattr(b, 'is_adjacent'):
-            if not b.is_adjacent(a):
-                b, c = c, b
-            elif not b.is_adjacent(c):
-                a, b = b, a
+        if not all_to_all_connect:
+            # Hacky magic: avoid the non-adjacent edge.
+            if hasattr(b, 'is_adjacent'):
+                if not b.is_adjacent(a):
+                    b, c = c, b
+                elif not b.is_adjacent(c):
+                    a, b = b, a
 
         p = common_gates.T**self._exponent
         sweep_abc = [common_gates.CNOT(a, b), common_gates.CNOT(b, c)]
         global_phase = 1j ** (2 * self.global_shift * self._exponent)
         global_phase = (
             complex(global_phase)
-            if protocols.is_parameterized(global_phase) and global_phase.is_complex
+            if protocols.is_parameterized(global_phase) and global_phase.is_complex  # type: ignore
             else global_phase
         )
         global_phase_operation = (
             [global_phase_op.global_phase_operation(global_phase)]
             if protocols.is_parameterized(global_phase) or abs(global_phase - 1.0) > 0
             else []
         )
+
+        if all_to_all_connect:
+            return global_phase_operation + [
+                common_gates.CNOT(b, c),
+                p(c) ** -1,
+                common_gates.CNOT(a, c),
+                p(c),
+                common_gates.CNOT(b, c),
+                p(c) ** -1,
+                common_gates.CNOT(a, c),
+                p(b),
+                p(c),
+                common_gates.CNOT(a, b),
+                p(a),
+                p(b) ** -1,
+                common_gates.CNOT(a, b),
+            ]
         return global_phase_operation + [
             p(a),
             p(b),

cirq-core/cirq/ops/three_qubit_gates_test.py

@@ -228,6 +228,20 @@ def test_decomposition_respects_locality(gate):
         dev.validate_circuit(circuit)
 
 
+def test_decomposition_all_to_all_connectivity():
+    decompose_result = cirq.CCZ._decompose_(cirq.LineQubit.range(3), all_to_all_connect=True)
+    cirq.testing.assert_has_diagram(
+        cirq.Circuit(decompose_result),
+        """
+0: ──────────────@──────────────────@───@───T──────@───
+                 │                  │   │          │
+1: ───@──────────┼───────@───T──────┼───X───T^-1───X───
+      │          │       │          │
+2: ───X───T^-1───X───T───X───T^-1───X───T──────────────
+""",
+    )
+
+
 def test_diagram():
     a, b, c, d = cirq.LineQubit.range(4)
     circuit = cirq.Circuit(