Add support for C(BlockEncode)

.github/CHANGELOG.md

@@ -8,6 +8,9 @@
 * Add `cutensornet` backed `MPS` C++ layer to `lightning.tensor`.
   [(#704)](https://github.com/PennyLaneAI/pennylane-lightning/pull/704)
 
+* Add support for `C(BlockEncode)` to Lightning devices.
+  [(#743)](https://github.com/PennyLaneAI/pennylane-lightning/pull/743)
+
 ### Breaking changes
 
 * Removed the `QuimbMPS` class and the corresponding interface/backend from `lightning.tensor`.

pennylane_lightning/core/_version.py

@@ -16,4 +16,4 @@
    Version number (major.minor.patch[-label])
 """
 
-__version__ = "0.37.0-dev23"
+__version__ = "0.37.0-dev24"

pennylane_lightning/lightning_gpu/lightning_gpu.py

@@ -174,6 +174,7 @@ def _mebibytesToBytes(mebibytes):
     "QFT",
     "ECR",
     "BlockEncode",
+    "C(BlockEncode)",
 }
 
 allowed_observables = {

pennylane_lightning/lightning_gpu/lightning_gpu.toml

@@ -58,7 +58,8 @@ MultiControlledX       = {}
 # Gates which should be translated to QubitUnitary
 [operators.gates.matrix]
 
-
+BlockEncode            = {properties = [ "controllable" ]}
+GlobalPhase            = {properties = [ "controllable" ]}
 ControlledQubitUnitary = {}
 ECR                    = {}
 SX                     = {}
@@ -70,7 +71,6 @@ OrbitalRotation        = {}
 QubitCarry             = {}
 QubitSum               = {}
 DiagonalQubitUnitary   = {}
-BlockEncode            = {}
 
 # Observables supported by the device
 [operators.observables]

pennylane_lightning/lightning_kokkos/lightning_kokkos.py

@@ -131,6 +131,7 @@ def _kokkos_configuration():
     "QFT",
     "ECR",
     "BlockEncode",
+    "C(BlockEncode)",
 }
 
 allowed_observables = {

pennylane_lightning/lightning_kokkos/lightning_kokkos.toml

@@ -58,7 +58,8 @@ StatePrep              = {}
 # Gates which should be translated to QubitUnitary
 [operators.gates.matrix]
 
-BlockEncode            = {}
+BlockEncode            = {properties = [ "controllable" ]}
+GlobalPhase            = {properties = [ "controllable" ]}
 DiagonalQubitUnitary   = {}
 ECR                    = {}
 ISWAP                  = {}

pennylane_lightning/lightning_qubit/lightning_qubit.py

@@ -289,6 +289,7 @@ def simulate_and_vjp(
         "QFT",
         "ECR",
         "BlockEncode",
+        "C(BlockEncode)",
     }
 )
 # The set of supported operations.

pennylane_lightning/lightning_qubit/lightning_qubit.toml

@@ -53,7 +53,7 @@ QFT                    = {}
 # Gates which should be translated to QubitUnitary
 [operators.gates.matrix]
 
-BlockEncode            = {}
+BlockEncode            = {properties = [ "controllable" ]}
 DiagonalQubitUnitary   = {}
 ECR                    = {}
 ISWAP                  = {}

tests/test_apply.py

@@ -1262,6 +1262,42 @@ def circuit():
         assert np.allclose(res_sv, expected_sv, atol=tol, rtol=0)
         assert np.allclose(res_probs, expected_prob, atol=tol, rtol=0)
 
+    # Check the BlockEncode PennyLane page for details:
+    # https://docs.pennylane.ai/en/stable/code/api/pennylane.BlockEncode.html
+    @pytest.mark.parametrize(
+        "op, op_wires",
+        [
+            [qml.BlockEncode, [0, 2]],
+            [qml.ctrl(qml.BlockEncode, control=(1)), [0, 2]],
+            [qml.ctrl(qml.BlockEncode, control=(2)), [0, 1]],
+        ],
+    )
+    @pytest.mark.parametrize(
+        "A",
+        [
+            np.array([[1, 1], [1, -1]]) / np.sqrt(2),
+            np.array([[1, 1], [1, -1]]),
+        ],
+    )
+    def test_apply_BlockEncode(self, op, op_wires, A, qubit_device, tol):
+        """Test apply BlockEncode and C(BlockEncode)"""
+
+        num_wires = 3
+        dev = qubit_device(wires=num_wires)
+
+        def circuit1(A):
+            qml.Hadamard(0)
+            qml.Hadamard(1)
+            op(A, wires=op_wires)
+            return qml.state()
+
+        results = qml.qnode(dev)(circuit1)(A)
+
+        dev_default = qml.device("default.qubit", wires=num_wires)
+        expected = qml.qnode(dev_default)(circuit1)(A)
+
+        assert np.allclose(results, expected, atol=tol, rtol=0)
+
 
 class TestApplyLightningMethod:
     """Unit tests for the apply_lightning method."""