Remove the pad argument from amplitude embedding template

doc/releases/changelog-dev.md

@@ -848,6 +848,10 @@
   Please use the `qml.metric_tensor` transform instead.
   [(#1638)](https://github.com/PennyLaneAI/pennylane/pull/1638)
 
+* The `pad` parameter of the `qml.AmplitudeEmbedding` template has been removed.
+  It has instead been renamed to the `pad_with` parameter.
+  [(#1805)](https://github.com/PennyLaneAI/pennylane/pull/1805)
+
 <h3>Bug fixes</h3>
 
 * Fixes a bug where the GPU cannot be used with `qml.qnn.TorchLayer`.
@@ -901,6 +905,6 @@
 
 This release contains contributions from (in alphabetical order):
 
-Utkarsh Azad, Akash Narayanan B, Sam Banning, Thomas Bromley, Olivia Di Matteo, Andrew Gardhouse, David Ittah, Josh Izaac, Christina Lee,
-Romain Moyard, Carrie-Anne Rubidge, Maria Schuld, Rishabh Singh, Ingrid Strandberg, Antal Száva, Cody Wang,
-David Wierichs, Moritz Willmann.
+Utkarsh Azad, Akash Narayanan B, Sam Banning, Thomas Bromley, Olivia Di Matteo, Andrew Gardhouse, David Ittah, 
+Josh Izaac, Christina Lee, Romain Moyard, Carrie-Anne Rubidge, Maria Schuld, Rishabh Singh, Jay Soni, Ingrid Strandberg, 
+Antal Száva, Cody Wang, David Wierichs, Moritz Willmann.

pennylane/templates/embeddings/amplitude.py

@@ -15,7 +15,6 @@
 Contains the AmplitudeEmbedding template.
 """
 # pylint: disable-msg=too-many-branches,too-many-arguments,protected-access
-import warnings
 import numpy as np
 
 import pennylane as qml
@@ -52,7 +51,6 @@ class AmplitudeEmbedding(Operation):
         wires (Iterable): wires that the template acts on
         pad_with (float or complex): if not None, the input is padded with this constant to size :math:`2^n`
         normalize (bool): whether to automatically normalize the features
-        pad (float or complex): same as `pad`, to be deprecated
 
     Example:
 
@@ -125,18 +123,7 @@ def circuit(f=None):
     par_domain = "A"
     grad_method = None
 
-    def __init__(
-        self, features, wires, pad_with=None, normalize=False, pad=None, do_queue=True, id=None
-    ):
-
-        # pad is replaced with the more verbose pad_with
-        if pad is not None:
-            warnings.warn(
-                "The pad argument will be replaced by the pad_with option in future versions of PennyLane.",
-                UserWarning,
-            )
-            if pad_with is None:
-                pad_with = pad
+    def __init__(self, features, wires, pad_with=None, normalize=False, do_queue=True, id=None):
 
         wires = Wires(wires)
         self.pad_with = pad_with
@@ -163,7 +150,8 @@ def _preprocess(features, wires, pad_with, normalize):
         * Check that the features tensor is one-dimensional.
         * If pad_with is None, check that the first dimension of the features tensor
           has length :math:`2^n` where :math:`n` is the number of qubits. Else check that the
-          first dimension of the features tensor is not larger than :math:`2^n` and pad features with value if necessary.
+          first dimension of the features tensor is not larger than :math:`2^n` and pad features
+          with value if necessary.
         * If normalize is false, check that first dimension of features is normalised to one. Else, normalise the
           features tensor.
         """
@@ -185,7 +173,7 @@ def _preprocess(features, wires, pad_with, normalize):
             if pad_with is None and n_features != 2 ** len(wires):
                 raise ValueError(
                     f"Features must be of length {2 ** len(wires)}; got length {n_features}. "
-                    f"Use the 'pad' argument for automated padding."
+                    f"Use the 'pad_with' argument for automated padding."
                 )
 
             if pad_with is not None and n_features > 2 ** len(wires):

pennylane/transforms/qfunc_transforms.py

@@ -16,7 +16,6 @@
 from copy import deepcopy
 import functools
 import inspect
-import types
 
 import pennylane as qml
 

tests/templates/test_embeddings/test_amplitude.py

@@ -220,24 +220,6 @@ def circuit(x=None):
         # No normalization error is raised
         circuit(x=inputs)
 
-    def test_deprecated_pad_arg(self):
-        """Test that the pad argument raises a deprecation warning"""
-
-        num_qubits = 2
-        dev = qml.device("default.qubit", wires=num_qubits)
-        inputs = np.array([1.0, 0.0, 0.0, 0.0])
-
-        @qml.qnode(dev)
-        def circuit(x=None):
-            qml.AmplitudeEmbedding(x, list(range(num_qubits)), pad=0.0, normalize=True)
-            return qml.expval(qml.PauliZ(0))
-
-        with pytest.warns(
-            UserWarning,
-            match="will be replaced by the pad_with option in future versions",
-        ):
-            circuit(x=inputs)
-
     def test_id(self):
         """Tests that the id attribute can be set."""
         template = qml.AmplitudeEmbedding(np.array([1, 0]), wires=[0], id="a")