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

cirq-core/cirq/ops/__init__.py

@@ -201,6 +201,7 @@
     CCXPowGate,
     CCZ,
     CCZPowGate,
+    decompose_all_to_all_connect_ccz_gate,
     CSWAP,
     CSwapGate,
     FREDKIN,

cirq-core/cirq/ops/three_qubit_gates.py

@@ -217,6 +217,55 @@ def controlled(
         )
 
 
+def decompose_all_to_all_connect_ccz_gate(
+    ccz_gate: 'CCZPowGate', qubits: Tuple['cirq.Qid', ...]
+) -> 'cirq.OP_TREE':
+    """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──────────────
+
+    where p = T**ccz_gate._exponent
+    """
+    if len(qubits) != 3:
+        raise ValueError(f'Expect 3 qubits for CCZ gate, got {len(qubits)} qubits.')
+
+    a, b, c = qubits
+
+    p = common_gates.T**ccz_gate._exponent
+    global_phase = 1j ** (2 * ccz_gate.global_shift * ccz_gate._exponent)
+    global_phase = (
+        complex(global_phase)
+        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 []
+    )
+
+    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),
+    ]
+
+
 @value.value_equality()
 class ThreeQubitDiagonalGate(raw_types.Gate):
     r"""A three qubit gate whose unitary is given by a diagonal $8 \times 8$ matrix.

cirq-core/cirq/ops/three_qubit_gates_test.py

@@ -230,6 +230,28 @@ def test_decomposition_respects_locality(gate):
         dev.validate_circuit(circuit)
 
 
+def test_decomposition_all_to_all_connectivity():
+    """This function only accepts 3 qubits as input"""
+    with pytest.raises(ValueError):
+        decompose_result = cirq.ops.decompose_all_to_all_connect_ccz_gate(
+            cirq.CCZ, cirq.LineQubit.range(4)
+        )
+
+    decompose_result = cirq.ops.decompose_all_to_all_connect_ccz_gate(
+        cirq.CCZ, cirq.LineQubit.range(3)
+    )
+    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(

cirq-ionq/cirq_ionq/ionq_gateset.py

@@ -78,12 +78,20 @@ def _decompose_two_qubit_operation(self, op: cirq.Operation, _) -> cirq.OP_TREE:
             temp, k=1, rewriter=lambda op: self._decompose_single_qubit_operation(op, -1)
         ).all_operations()
 
+    def _decompose_multi_qubit_operation(self, op: cirq.Operation, _) -> cirq.OP_TREE:
+        if isinstance(op.gate, cirq.CCZPowGate):
+            return cirq.ops.decompose_all_to_all_connect_ccz_gate(op.gate, op.qubits)
+        return NotImplemented
+
     @property
     def preprocess_transformers(self) -> List['cirq.TRANSFORMER']:
-        """List of transformers which should be run before decomposing individual operations."""
+        """List of transformers which should be run before decomposing individual operations.
+        Decompose to three qubit gates because three qubit gates have different decomposition
+        for all-to-all connectivity between qubits.
+        """
         return [
             cirq.create_transformer_with_kwargs(
-                cirq.expand_composite, no_decomp=lambda op: cirq.num_qubits(op) <= self.num_qubits
+                cirq.expand_composite, no_decomp=lambda op: cirq.num_qubits(op) <= 3
             )
         ]
 

cirq-ionq/cirq_ionq/ionq_gateset_test.py

@@ -131,3 +131,24 @@ def test_decompose_parameterized_operation():
             atol=1e-6,
         )
     assert ionq_target_gateset.validate(decomposed_circuit)
+
+
+def test_decompose_toffoli_gate():
+    circuit = cirq.Circuit(cirq.TOFFOLI(*cirq.LineQubit.range(3)))
+    decomposed_circuit = cirq.optimize_for_target_gateset(
+        circuit, gateset=ionq_target_gateset, ignore_failures=False
+    )
+    cirq.testing.assert_circuits_with_terminal_measurements_are_equivalent(
+        circuit, decomposed_circuit, atol=1e-8
+    )
+    assert ionq_target_gateset.validate(decomposed_circuit)
+    cirq.testing.assert_has_diagram(
+        decomposed_circuit,
+        """
+0: ──────────────────@──────────────────@───@───T──────@───
+                     │                  │   │          │
+1: ───────@──────────┼───────@───T──────┼───X───T^-1───X───
+          │          │       │          │
+2: ───H───X───T^-1───X───T───X───T^-1───X───T───H──────────
+""",
+    )