remove default.qubit.autograd (#6210)

[sc-72795] --------- Co-authored-by: Pietropaolo Frisoni <pietropaolo.frisoni@xanadu.ai>
PennyLaneAI · Sep 13, 2024 · 08961dd · 08961dd
1 parent 1cbaeec
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diff --git a/Makefile b/Makefile
@@ -60,12 +60,10 @@ clean-docs:
 
 test:
 	$(PYTHON) $(TESTRUNNER)
-	$(PYTHON) $(PLUGIN_TESTRUNNER) --device=default.qubit.autograd
 
 coverage:
 	@echo "Generating coverage report..."
 	$(PYTHON) $(TESTRUNNER) $(COVERAGE)
-	$(PYTHON) $(PLUGIN_TESTRUNNER) --device=default.qubit.autograd $(COVERAGE) --cov-append
 
 .PHONY:format
 format:

diff --git a/doc/development/deprecations.rst b/doc/development/deprecations.rst
@@ -15,18 +15,6 @@ Pending deprecations
   - Deprecated in v0.39
   - Will be removed in v0.40
 
-* All of the legacy devices (any with the name ``default.qubit.{autograd,torch,tf,jax,legacy}``) are deprecated. Use ``default.qubit`` instead,
-  as it supports backpropagation for the many backends the legacy devices support.
-
-  - Deprecated in v0.38
-  - Will be removed in v0.39
-
-* The logic for internally switching a device for a different backpropagation
-  compatible device is now deprecated, as it was in place for the deprecated ``default.qubit.legacy``.
-
-  - Deprecated in v0.38
-  - Will be removed in v0.39  
-
 * The ``decomp_depth`` argument in ``qml.device`` is deprecated. 
 
   - Deprecated in v0.38
@@ -88,6 +76,18 @@ Other deprecations
 Completed deprecation cycles
 ----------------------------
 
+* All of the legacy devices (any with the name ``default.qubit.{autograd,torch,tf,jax,legacy}``) are removed. Use ``default.qubit`` instead,
+  as it supports backpropagation for the many backends the legacy devices support.
+
+  - Deprecated in v0.38
+  - Removed in v0.39
+
+* The logic for internally switching a device for a different backpropagation
+  compatible device is removed, as it was in place for removed ``default.qubit.legacy``.
+
+  - Deprecated in v0.38
+  - Removed in v0.39
+
 * `Operator.expand` is now removed. Use `qml.tape.QuantumScript(op.deocomposition())` instead.
 
   - Deprecated in v0.38

diff --git a/doc/releases/changelog-dev.md b/doc/releases/changelog-dev.md
@@ -59,10 +59,12 @@
 * Remove support for Python 3.9.
   [(#6223)](https://github.com/PennyLaneAI/pennylane/pull/6223)
 
-* `DefaultQubitTF`, `DefaultQubitTorch`, and `DefaultQubitJax` are removed. Please use `default.qubit` for all interfaces.
+* `DefaultQubitTF`, `DefaultQubitTorch`, `DefaultQubitJax`, and `DefaultQubitAutograd` are removed.
+  Please use `default.qubit` for all interfaces.
   [(#6207)](https://github.com/PennyLaneAI/pennylane/pull/6207)
   [(#6208)](https://github.com/PennyLaneAI/pennylane/pull/6208)
   [(#6209)](https://github.com/PennyLaneAI/pennylane/pull/6209)
+  [(#6210)](https://github.com/PennyLaneAI/pennylane/pull/6210)
 
 * `expand_fn`, `max_expansion`, `override_shots`, and `device_batch_transform` are removed from the
   signature of `qml.execute`.
@@ -81,6 +83,7 @@
 * `Operator.expand` is now removed. Use `qml.tape.QuantumScript(op.deocomposition())` instead.
   [(#6227)](https://github.com/PennyLaneAI/pennylane/pull/6227)
 
+
 <h3>Deprecations 👋</h3>
 
 * `QNode.gradient_fn` is deprecated. Please use `QNode.diff_method` and `QNode.get_gradient_fn` instead.

diff --git a/pennylane/devices/__init__.py b/pennylane/devices/__init__.py
@@ -27,7 +27,6 @@
 
     default_qubit
     default_qubit_legacy
-    default_qubit_autograd
     default_gaussian
     default_mixed
     default_qutrit
@@ -153,9 +152,6 @@ def execute(self, circuits, execution_config = qml.devices.DefaultExecutionConfi
 from .default_qubit import DefaultQubit
 from .legacy_facade import LegacyDeviceFacade
 
-# DefaultQubitTF and DefaultQubitAutograd not imported here since this
-# would lead to an automatic import of tensorflow and autograd, which are
-# not PennyLane core dependencies.
 # DefaultTensor is not imported here to avoid warnings
 # from quimb in case it is installed on the system.
 from .default_qubit_legacy import DefaultQubitLegacy

diff --git a/pennylane/devices/default_qubit_autograd.py b/pennylane/devices/default_qubit_autograd.py
diff --git a/pennylane/devices/default_qubit_legacy.py b/pennylane/devices/default_qubit_legacy.py
@@ -713,9 +713,7 @@ def capabilities(cls):
             supports_analytic_computation=True,
             supports_broadcasting=True,
             returns_state=True,
-            passthru_devices={
-                "autograd": "default.qubit.autograd",
-            },
+            passthru_devices={},
         )
         return capabilities
 

diff --git a/pennylane/devices/legacy_facade.py b/pennylane/devices/legacy_facade.py
@@ -15,7 +15,6 @@
 Defines a LegacyDeviceFacade class for converting legacy devices to the
 new interface.
 """
-import warnings
 
 # pylint: disable=not-callable, unused-argument
 from contextlib import contextmanager
@@ -318,79 +317,6 @@ def supports_derivatives(self, execution_config=None, circuit=None) -> bool:
 
         return False
 
-    # pylint: disable=protected-access
-    def _create_temp_device(self, batch):
-        """Create a temporary device for use in a backprop execution."""
-        params = []
-        for t in batch:
-            params.extend(t.get_parameters(trainable_only=False))
-        interface = qml.math.get_interface(*params)
-        if interface == "numpy":
-            return self._device
-
-        mapped_interface = qml.workflow.execution.INTERFACE_MAP.get(interface, interface)
-
-        backprop_interface = self._device.capabilities().get("passthru_interface", None)
-        if mapped_interface == backprop_interface:
-            return self._device
-
-        backprop_devices = self._device.capabilities().get("passthru_devices", None)
-
-        if backprop_devices is None:
-            raise qml.DeviceError(f"Device {self} does not support backpropagation.")
-
-        if backprop_devices[mapped_interface] == self._device.short_name:
-            return self._device
-
-        if self.target_device.short_name != "default.qubit.legacy":
-            warnings.warn(
-                "The switching of devices for backpropagation is now deprecated in v0.38 and "
-                "will be removed in v0.39, as this behavior was developed purely for the "
-                "deprecated default.qubit.legacy.",
-                qml.PennyLaneDeprecationWarning,
-            )
-
-        # create new backprop device
-        expand_fn = self._device.expand_fn
-        batch_transform = self._device.batch_transform
-        if hasattr(self._device, "_debugger"):
-            debugger = self._device._debugger
-        else:
-            debugger = "No debugger"
-        tracker = self._device.tracker
-
-        with warnings.catch_warnings():
-            warnings.filterwarnings(
-                action="ignore",
-                category=qml.PennyLaneDeprecationWarning,
-                message=r"use 'default.qubit'",
-            )
-            # we already warned about backprop device switching
-            new_device = qml.device(
-                backprop_devices[mapped_interface],
-                wires=self._device.wires,
-                shots=self._device.shots,
-            ).target_device
-
-        new_device.expand_fn = expand_fn
-        new_device.batch_transform = batch_transform
-        if debugger != "No debugger":
-            new_device._debugger = debugger
-        new_device.tracker = tracker
-
-        return new_device
-
-    # pylint: disable=protected-access
-    def _update_original_device(self, temp_device):
-        """After performing an execution with a backprop device, update the state of the original device."""
-        # Update for state vector simulators that have the _pre_rotated_state attribute
-        if hasattr(self._device, "_pre_rotated_state"):
-            self._device._pre_rotated_state = temp_device._pre_rotated_state
-
-        # Update for state vector simulators that have the _state attribute
-        if hasattr(self._device, "_state"):
-            self._device._state = temp_device._state
-
     def _validate_backprop_method(self, tape):
         if tape.shots:
             return False
@@ -441,28 +367,18 @@ def _validate_device_method(self, _):
         return self._device.capabilities().get("provides_jacobian", False)
 
     def execute(self, circuits, execution_config=DefaultExecutionConfig):
-        dev = (
-            self._create_temp_device(circuits)
-            if execution_config.gradient_method == "backprop"
-            else self._device
-        )
+        dev = self.target_device
 
         kwargs = {}
         if dev.capabilities().get("supports_mid_measure", False):
             kwargs["postselect_mode"] = execution_config.mcm_config.postselect_mode
 
         first_shot = circuits[0].shots
         if all(t.shots == first_shot for t in circuits):
-            results = _set_shots(dev, first_shot)(dev.batch_execute)(circuits, **kwargs)
-        else:
-            results = tuple(
-                _set_shots(dev, t.shots)(dev.batch_execute)((t,), **kwargs)[0] for t in circuits
-            )
-
-        if dev is not self._device:
-            self._update_original_device(dev)
-
-        return results
+            return _set_shots(dev, first_shot)(dev.batch_execute)(circuits, **kwargs)
+        return tuple(
+            _set_shots(dev, t.shots)(dev.batch_execute)((t,), **kwargs)[0] for t in circuits
+        )
 
     def execute_and_compute_derivatives(self, circuits, execution_config=DefaultExecutionConfig):
         first_shot = circuits[0].shots

diff --git a/pennylane/devices/tests/conftest.py b/pennylane/devices/tests/conftest.py
@@ -36,7 +36,6 @@
 # List of all devices that are included in PennyLane
 LIST_CORE_DEVICES = {
     "default.qubit",
-    "default.qubit.autograd",
 }
 
 

diff --git a/pennylane/tape/qscript.py b/pennylane/tape/qscript.py
@@ -555,7 +555,7 @@ def trainable_params(self) -> list[int]:
         .. note::
 
             For devices that support native backpropagation (such as
-            ``default.qubit.tf`` and ``default.qubit.autograd``), this
+            ``default.qubit`` and ``default.mixed``), this
             property contains no relevant information when using
             backpropagation to compute gradients.
 

diff --git a/pennylane/workflow/execution.py b/pennylane/workflow/execution.py
@@ -165,7 +165,7 @@ def _get_ml_boundary_execute(
             else:
                 from .interfaces.jax import jax_jvp_execute as ml_boundary
 
-    except ImportError as e:  # pragma: no-cover
+    except ImportError as e:  # pragma: no cover
         raise qml.QuantumFunctionError(
             f"{mapped_interface} not found. Please install the latest "
             f"version of {mapped_interface} to enable the '{mapped_interface}' interface."

diff --git a/setup.py b/setup.py
@@ -51,7 +51,6 @@
             "default.qubit = pennylane.devices:DefaultQubit",
             "default.qubit.legacy = pennylane.devices:DefaultQubitLegacy",
             "default.gaussian = pennylane.devices:DefaultGaussian",
-            "default.qubit.autograd = pennylane.devices.default_qubit_autograd:DefaultQubitAutograd",
             "default.mixed = pennylane.devices.default_mixed:DefaultMixed",
             "null.qubit = pennylane.devices.null_qubit:NullQubit",
             "default.qutrit = pennylane.devices.default_qutrit:DefaultQutrit",