def BasisEmbedding(features, wires):
r"""Encodes :math:`n` binary features into a basis state of :math:`n` qubits.
For example, for ``features=np.array([0, 1, 0])``, the quantum system will be
prepared in state :math:`|010 \rangle`.
.. warning::
``BasisEmbedding`` calls a circuit whose architecture depends on the binary features.
The ``features`` argument is therefore not differentiable when using the template, and
gradients with respect to the argument cannot be computed by PennyLane.
Args:
features (array): binary input array of shape ``(n, )``
wires (Sequence[int] or int): qubit indices that the template acts on
Raises:
ValueError: if inputs do not have the correct format
"""
#############
# Input checks
wires, n_wires = _check_wires(wires)
_check_shape(features, (n_wires,))
# basis_state is guaranteed to be a list
if any([b not in [0, 1] for b in features]):
raise ValueError("Basis state must only consist of 0s and 1s, got {}".format(features))
###############
features = np.array(features)
BasisState(features, wires=wires)
def BasisEmbedding(features, wires):
r"""Encodes :math:`n` binary features into a basis state of :math:`n` qubits.
For example, for ``features=[0, 1, 0]``, the quantum system will be prepared in state :math:`|010 \rangle`.
.. note::
BasisEmbedding uses PennyLane's :class:`~pennylane.ops.BasisState` and only works in conjunction with
devices that implement this function.
Args:
features (array): Binary input array of shape ``(n, )``
wires (Sequence[int]): sequence of qubit indices that the template acts on
Raises:
ValueError: if ``features`` or ``wires`` is invalid
"""
if not isinstance(wires, Iterable):
raise ValueError(
"Wires must be passed as a list of integers; got {}.".format(
wires))
if len(features) > len(wires):
raise ValueError(
"Number of bits to embed cannot be larger than number of wires, which is {}; "
"got {}.".format(len(wires), len(features)))
BasisState(features, wires=wires)
def expand(self):
weights = self.parameters[0]
with qml.tape.QuantumTape() as tape:
BasisState(self.hf_state, wires=self.wires)
for i, d_wires in enumerate(self.doubles):
qml.DoubleExcitation(weights[len(self.singles) + i], wires=d_wires)
for j, s_wires in enumerate(self.singles):
qml.SingleExcitation(weights[j], wires=s_wires)
return tape
def expand(self):
weights = self.parameters[0]
with qml.tape.QuantumTape() as tape:
BasisState(self.init_state_flipped, wires=self.wires)
for i, (w1, w2) in enumerate(self.d_wires):
qml.templates.DoubleExcitationUnitary(
weights[len(self.s_wires) + i], wires1=w1, wires2=w2)
for j, s_wires_ in enumerate(self.s_wires):
qml.templates.SingleExcitationUnitary(weights[j],
wires=s_wires_)
return tape