Remove CPhase gate alias references (#718)

**Context:** Transition to the quantum device config schema 2

**Description of the Change:**

* Remove mentions of CPhase "gate" which happens to be a Python alias
for ControlledPhaseShift.
* Remove the Python-only Projector patch because we already have a
relaxed validation procedure for observables
* Relax operation validation by allowing kokkos device to declare
C(GlobalPhase) which is a Python-only operation.

**Benefits:**
**Possible Drawbacks:** 
**Related GitHub Issues:**

* PennyLaneAI/pennylane-lightning#642
- (related discussion)
PennyLaneAI/pennylane-lightning#642 (comment)

Author: Sergei Mironov

frontend/catalyst/device/qjit_device.py

@@ -492,10 +492,16 @@ def validate_device_capabilities(
     if hasattr(device, "operations") and hasattr(device, "observables"):
         # For gates, we require strict match
         device_gates = filter_out_adjoint(set(device.operations))
+        # Lightning-kokkis might support C(GlobalPhase) in Python, but not in C++. We remove this
+        # gate before calling the validation.
+        # See https://github.com/PennyLaneAI/pennylane-lightning/pull/642#discussion_r1535478642
+        if device_name == "lightning.kokkos":
+            device_gates = device_gates - {"C(GlobalPhase)"}
         spec_gates = filter_out_adjoint(set.union(native, matrix, decomposable))
         if device_gates != spec_gates:
             raise CompileError(
-                "Gates in qml.device.operations and specification file do not match.\n"
+                "Gates in qml.device.operations and specification file do not match for "
+                f'"{device_name}".\n'
                 f"Gates that present only in the device: {device_gates - spec_gates}\n"
                 f"Gates that present only in spec: {spec_gates - device_gates}\n"
             )

frontend/catalyst/utils/toml.py

@@ -260,24 +260,10 @@ def get_operation_properties(config_props: dict) -> OperationProperties:
 
 
 def patch_schema1_collections(
-    config, device_name, native_gate_props, matrix_decomp_props, decomp_props, observable_props
+    config, _device_name, native_gate_props, matrix_decomp_props, decomp_props
 ):  # pylint: disable=too-many-arguments, too-many-branches
     """For old schema1 config files we deduce some information which was not explicitly encoded."""
 
-    # TODO: remove after PR #642 is merged in lightning
-    # NOTE: we mark GlobalPhase as controllables even if `quantum_control` flag is False. This
-    # is what actual device reports.
-    if device_name == "lightning.kokkos":  # pragma: nocover
-        native_gate_props["GlobalPhase"] = OperationProperties(
-            invertible=False, controllable=True, differentiable=True
-        )
-
-    # TODO: remove after PR #642 is merged in lightning
-    if device_name == "lightning.kokkos":  # pragma: nocover
-        observable_props["Projector"] = OperationProperties(
-            invertible=False, controllable=False, differentiable=False
-        )
-
     # The deduction logic is the following:
     # * Most of the gates have their `C(Gate)` controlled counterparts.
     # * Some gates have to be decomposed if controlled version is used. Typically these are
@@ -414,7 +400,6 @@ def load_device_capabilities(
             native_gate_props,
             matrix_decomp_props,
             decomp_props,
-            observable_props,
         )
 
     return DeviceCapabilities(

frontend/test/pytest/test_custom_devices.py

@@ -60,7 +60,6 @@
     "PSWAP",
     "SISWAP",
     "SQISW",
-    "CPhase",
     "BasisState",
     "QubitStateVector",
     "StatePrep",

runtime/lib/backend/dummy/dummy_device.toml

@@ -19,7 +19,6 @@ CY = { properties = [ "invertible", "differentiable" ] }
 CZ = { properties = [ "invertible", "differentiable" ] }
 PhaseShift = { properties = [ "controllable", "invertible", "differentiable" ] }
 ControlledPhaseShift = { properties = [ "invertible", "differentiable" ] }
-CPhase = { properties = [ "invertible", "differentiable" ] }
 RX = { properties = [ "controllable", "invertible", "differentiable" ] }
 RY = { properties = [ "controllable", "invertible", "differentiable" ] }
 RZ = { properties = [ "controllable", "invertible", "differentiable" ] }