Source code for pennylane.io.io
# Copyright 2018-2021 Xanadu Quantum Technologies Inc.
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
# http://www.apache.org/licenses/LICENSE-2.0
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
This module contains functions to load circuits from other frameworks as
PennyLane templates.
"""
from collections import defaultdict
from collections.abc import Callable
from importlib import metadata
from sys import version_info
has_openqasm = True
try:
import openqasm3
from pennylane.io.qasm_interpreter import QasmInterpreter
except (ModuleNotFoundError, ImportError) as import_error: # pragma: no cover
has_openqasm = False # pragma: no cover
# Error message to show when the PennyLane-Qiskit plugin is required but missing.
_MISSING_QISKIT_PLUGIN_MESSAGE = (
"Conversion from Qiskit requires the PennyLane-Qiskit plugin. "
"You can install the plugin by running: pip install pennylane-qiskit. "
"You may need to restart your kernel or environment after installation. "
"If you have any difficulties, you can reach out on the PennyLane forum at "
"https://discuss.pennylane.ai/c/pennylane-plugins/pennylane-qiskit/"
)
# get list of installed plugin converters
__plugin_devices = (
defaultdict(tuple, metadata.entry_points())["pennylane.io"]
if version_info[:2] == (3, 9)
else metadata.entry_points(group="pennylane.io")
)
plugin_converters = {entry.name: entry for entry in __plugin_devices}
[docs]
def from_qiskit(quantum_circuit, measurements=None):
r"""Converts a Qiskit `QuantumCircuit <https://docs.quantum.ibm.com/api/qiskit/qiskit.circuit.QuantumCircuit>`_
into a PennyLane :ref:`quantum function <intro_vcirc_qfunc>`.
.. note::
This function depends upon the PennyLane-Qiskit plugin. Follow the
`installation instructions <https://docs.pennylane.ai/projects/qiskit/en/latest/installation.html>`__
to get up and running. You may need to restart your kernel if you are running in a notebook
environment.
Args:
quantum_circuit (qiskit.QuantumCircuit): a quantum circuit created in Qiskit
measurements (None | MeasurementProcess | list[MeasurementProcess]): an optional PennyLane
measurement or list of PennyLane measurements that overrides any terminal measurements
that may be present in the input circuit
Returns:
function: The PennyLane quantum function, created based on the input Qiskit
``QuantumCircuit`` object.
**Example:**
.. code-block:: python
import pennylane as qml
from qiskit import QuantumCircuit
qc = QuantumCircuit(2, 2)
qc.rx(0.785, 0)
qc.ry(1.57, 1)
my_qfunc = qml.from_qiskit(qc)
The ``my_qfunc`` function can now be used within QNodes, as a two-wire quantum
template. We can also pass ``wires`` when calling the returned template to define
which wires it should operate on. If no wires are passed, it will default
to sequential wire labels starting at 0.
.. code-block:: python
dev = qml.device("default.qubit")
@qml.qnode(dev)
def circuit():
my_qfunc(wires=["a", "b"])
return qml.expval(qml.Z("a")), qml.var(qml.Z("b"))
>>> circuit()
(tensor(0.70738827, requires_grad=True),
tensor(0.99999937, requires_grad=True))
The measurements can also be passed directly to the function when creating the
quantum function, making it possible to create a PennyLane circuit with
:class:`qml.QNode <pennylane.QNode>`:
>>> measurements = [qml.expval(qml.Z(0)), qml.var(qml.Z(1))]
>>> circuit = qml.QNode(qml.from_qiskit(qc, measurements), dev)
>>> circuit()
(tensor(0.70738827, requires_grad=True),
tensor(0.99999937, requires_grad=True))
.. note::
The ``measurements`` keyword allows one to add a list of PennyLane measurements
that will **override** any terminal measurements present in the ``QuantumCircuit``,
so that they are not performed before the operations specified in ``measurements``.
``measurements=None``.
If an existing ``QuantumCircuit`` already contains measurements, ``from_qiskit``
will return those measurements, provided that they are not overridden as shown above.
These measurements can be used, e.g., for conditioning with
:func:`qml.cond() <~.cond>`, or simply included directly within the QNode's return:
.. code-block:: python
qc = QuantumCircuit(2, 2)
qc.rx(np.pi, 0)
qc.measure_all()
@qml.qnode(dev)
def circuit():
# Since measurements=None, the measurements present in the QuantumCircuit are returned.
measurements = qml.from_qiskit(qc)()
return [qml.expval(m) for m in measurements]
>>> circuit()
[tensor(1., requires_grad=True), tensor(0., requires_grad=True)]
.. note::
The ``measurements`` returned from a ``QuantumCircuit`` are in the computational basis
with 0 corresponding to :math:`|0\rangle` and 1 corresponding to :math:`|1 \rangle`. This
corresponds to the :math:`|1 \rangle \langle 1|` observable rather than the :math:`Z` Pauli
operator.
See below for more information regarding how to translate more complex circuits from Qiskit to
PennyLane, including handling parametrized Qiskit circuits, mid-circuit measurements, and
classical control flows.
.. details::
:title: Parametrized Quantum Circuits
A Qiskit ``QuantumCircuit`` is parametrized if it contains
`Parameter <https://docs.quantum.ibm.com/api/qiskit/qiskit.circuit.Parameter>`__ or
`ParameterVector <https://docs.quantum.ibm.com/api/qiskit/qiskit.circuit.ParameterVector>`__
references that need to be given defined values to evaluate the circuit. These can be passed
to the generated quantum function as keyword or positional arguments. If we define a
parametrized circuit:
.. code-block:: python
from qiskit.circuit import QuantumCircuit, Parameter
angle0 = Parameter("x")
angle1 = Parameter("y")
qc = QuantumCircuit(2, 2)
qc.rx(angle0, 0)
qc.ry(angle1, 1)
qc.cx(1, 0)
Then this circuit can be converted into a differentiable circuit in PennyLane and
executed:
.. code-block:: python
import pennylane as qml
from pennylane import numpy as np
dev = qml.device("default.qubit")
qfunc = qml.from_qiskit(qc, measurements=qml.expval(qml.Z(0)))
circuit = qml.QNode(qfunc, dev)
Now, ``circuit`` has a signature of ``(x, y)``. The parameters are ordered alphabetically.
>>> x = np.pi / 4
>>> y = 0
>>> circuit(x, y)
tensor(0.70710678, requires_grad=True)
>>> qml.grad(circuit, argnum=[0, 1])(np.pi/4, np.pi/6)
(array(-0.61237244), array(-0.35355339))
The ``QuantumCircuit`` may also be parametrized with a ``ParameterVector``. These can be
similarly converted:
.. code-block:: python
from qiskit.circuit import ParameterVector
angles = ParameterVector("angles", 2)
qc = QuantumCircuit(2, 2)
qc.rx(angles[0], 0)
qc.ry(angles[1], 1)
qc.cx(1, 0)
@qml.qnode(dev)
def circuit(angles):
qml.from_qiskit(qc)(angles)
return qml.expval(qml.Z(0))
>>> angles = [3.1, 0.45]
>>> circuit(angles)
tensor(-0.89966835, requires_grad=True)
.. details::
:title: Measurements and Classical Control Flows
When ``measurement=None``, all of the measurements performed in the ``QuantumCircuit`` will
be returned by the quantum function in the form of a :ref:`mid-circuit measurement
<mid_circuit_measurements>`. For example, if we define a ``QuantumCircuit`` with
measurements:
.. code-block:: python
import pennylane as qml
from qiskit import QuantumCircuit
qc = QuantumCircuit(2, 2)
qc.h(0)
qc.measure(0, 0)
qc.rz(0.24, [0])
qc.cx(0, 1)
qc.measure_all()
Then we can create a PennyLane circuit that uses this as a sub-circuit, and performs
additional operations conditional on the results. We can also calculate standard mid-circuit
measurement statistics, like expectation value, on the returned measurements:
.. code-block:: python
@qml.qnode(qml.device("default.qubit"))
def circuit():
# apply the QuantumCircuit and retrieve the measurements
mid_measure0, m0, m1 = qml.from_qiskit(qc)()
# conditionally apply an additional operation based on the results
qml.cond(mid_measure0==0, qml.RX)(np.pi/2, 0)
# return the expectation value of one of the mid-circuit measurements, and a terminal measurement
return qml.expval(mid_measure0), qml.expval(m1)
>>> circuit()
(tensor(0.5, requires_grad=True), tensor(0.5, requires_grad=True))
.. note::
The order of mid-circuit measurements returned by `qml.from_qiskit()` in the example
above is determined by the order in which measurements appear in the input Qiskit
``QuantumCircuit``.
Furthermore, the Qiskit `IfElseOp <https://docs.quantum.ibm.com/api/qiskit/qiskit.circuit.IfElseOp>`__,
`SwitchCaseOp <https://docs.quantum.ibm.com/api/qiskit/qiskit.circuit.SwitchCaseOp>`__ and
`c_if <https://docs.quantum.ibm.com/api/qiskit/qiskit.circuit.Instruction#c_if>`__
conditional workflows are automatically translated into their PennyLane counterparts during
conversion. For example, if we construct a ``QuantumCircuit`` with these workflows:
.. code-block:: python
qc = QuantumCircuit(4, 1)
qc.h(0)
qc.measure(0, 0)
# Use an `IfElseOp` operation.
noop = QuantumCircuit(1)
flip_x = QuantumCircuit(1)
flip_x.x(0)
qc.if_else((qc.clbits[0], True), flip_x, noop, [1], [])
# Use a `SwitchCaseOp` operation.
with qc.switch(qc.clbits[0]) as case:
with case(0):
qc.y(2)
# Use the `c_if()` function.
qc.z(3).c_if(qc.clbits[0], True)
qc.measure_all()
We can convert the ``QuantumCircuit`` into a PennyLane quantum function using:
.. code-block:: python
dev = qml.device("default.qubit")
measurements = [qml.expval(qml.Z(i)) for i in range(qc.num_qubits)]
cond_circuit = qml.QNode(qml.from_qiskit(qc, measurements=measurements), dev)
The result is:
>>> print(qml.draw(cond_circuit)())
0: ──H──┤↗├──────────╭||─┤ <Z>
1: ──────║───X───────├||─┤ <Z>
2: ──────║───║──Y────├||─┤ <Z>
3: ──────║───║──║──Z─╰||─┤ <Z>
╚═══╩══╩══╝
"""
try:
plugin_converter = plugin_converters["qiskit"].load()
return plugin_converter(quantum_circuit, measurements=measurements)
except KeyError as e:
raise RuntimeError(_MISSING_QISKIT_PLUGIN_MESSAGE) from e
[docs]
def from_qiskit_op(qiskit_op, params=None, wires=None):
"""Converts a Qiskit `SparsePauliOp <https://docs.quantum.ibm.com/api/qiskit/qiskit.quantum_info.SparsePauliOp>`__
into a PennyLane :class:`Operator <pennylane.operation.Operator>`.
.. note::
This function depends upon the PennyLane-Qiskit plugin. Follow the
`installation instructions <https://docs.pennylane.ai/projects/qiskit/en/latest/installation.html>`__
to get up and running. You may need to restart your kernel if you are running in a notebook
environment.
Args:
qiskit_op (qiskit.quantum_info.SparsePauliOp): a ``SparsePauliOp`` created in Qiskit
params (Any): optional assignment of coefficient values for the ``SparsePauliOp``; see the
`Qiskit documentation <https://docs.quantum.ibm.com/api/qiskit/qiskit.quantum_info.SparsePauliOp#assign_parameters>`_
to learn more about the expected format of these parameters
wires (Sequence | None): optional assignment of wires for the converted ``SparsePauliOp``;
if the original ``SparsePauliOp`` acted on :math:`N` qubits, then this must be a
sequence of length :math:`N`
Returns:
Operator: The PennyLane operator, created based on the input Qiskit
``SparsePauliOp`` object.
.. note::
The wire ordering convention differs between PennyLane and Qiskit: PennyLane wires are
enumerated from left to right, while the Qiskit convention is to enumerate from right to
left. This means a ``SparsePauliOp`` term defined by the string ``"XYZ"`` applies ``Z`` on
wire 0, ``Y`` on wire 1, and ``X`` on wire 2. For more details, see the
`String representation <https://docs.quantum.ibm.com/api/qiskit/qiskit.quantum_info.Pauli>`_
section of the Qiskit documentation for the ``Pauli`` class.
**Example**
Consider the following script which creates a Qiskit ``SparsePauliOp``:
.. code-block:: python
from qiskit.quantum_info import SparsePauliOp
qiskit_op = SparsePauliOp(["II", "XY"])
The ``SparsePauliOp`` contains two terms and acts over two qubits:
>>> qiskit_op
SparsePauliOp(['II', 'XY'],
coeffs=[1.+0.j, 1.+0.j])
To convert the ``SparsePauliOp`` into a PennyLane :class:`pennylane.operation.Operator`, use:
>>> import pennylane as qml
>>> qml.from_qiskit_op(qiskit_op)
I(0) + X(1) @ Y(0)
.. details::
:title: Usage Details
You can convert a parametrized ``SparsePauliOp`` into a PennyLane operator by assigning
literal values to each coefficient parameter. For example, the script
.. code-block:: python
import numpy as np
from qiskit.circuit import Parameter
a, b, c = [Parameter(var) for var in "abc"]
param_qiskit_op = SparsePauliOp(["II", "XZ", "YX"], coeffs=np.array([a, b, c]))
defines a ``SparsePauliOp`` with three coefficients (parameters):
>>> param_qiskit_op
SparsePauliOp(['II', 'XZ', 'YX'],
coeffs=[ParameterExpression(1.0*a), ParameterExpression(1.0*b),
ParameterExpression(1.0*c)])
The ``SparsePauliOp`` can be converted into a PennyLane operator by calling the conversion
function and specifying the value of each parameter using the ``params`` argument:
>>> qml.from_qiskit_op(param_qiskit_op, params={a: 2, b: 3, c: 4})
(
(2+0j) * I(0)
+ (3+0j) * (X(1) @ Z(0))
+ (4+0j) * (Y(1) @ X(0))
)
Similarly, a custom wire mapping can be applied to a ``SparsePauliOp`` as follows:
>>> wired_qiskit_op = SparsePauliOp("XYZ")
>>> wired_qiskit_op
SparsePauliOp(['XYZ'],
coeffs=[1.+0.j])
>>> qml.from_qiskit_op(wired_qiskit_op, wires=[3, 5, 7])
Y(5) @ Z(3) @ X(7)
"""
try:
plugin_converter = plugin_converters["qiskit_op"].load()
return plugin_converter(qiskit_op, params=params, wires=wires)
except KeyError as e:
raise RuntimeError(_MISSING_QISKIT_PLUGIN_MESSAGE) from e
[docs]
def from_qiskit_noise(noise_model, verbose=False, decimal_places=None):
"""Converts a Qiskit `NoiseModel <https://qiskit.github.io/qiskit-aer/stubs/qiskit_aer.noise.NoiseModel.html>`__
into a PennyLane :class:`~.NoiseModel`.
Args:
noise_model (qiskit_aer.noise.NoiseModel): a Qiskit ``NoiseModel`` instance.
verbose (bool): when printing a ``NoiseModel``, a complete list of Kraus matrices for each ``qml.QubitChannel``
is displayed with ``verbose=True``. By default, ``verbose=False`` and only the number of Kraus matrices and
the number of qubits they act on is displayed for brevity.
decimal_places (int | None): number of decimal places to round the elements of Kraus matrices when they are being
displayed for each ``qml.QubitChannel`` when ``verbose=True``.
Returns:
qml.NoiseModel: The PennyLane noise model converted from the input Qiskit ``NoiseModel`` object.
Raises:
ValueError: When a quantum error present in the noise model cannot be converted.
.. note::
- This function depends upon the PennyLane-Qiskit plugin, which can be installed following these
`installation instructions <https://docs.pennylane.ai/projects/qiskit/en/latest/installation.html>`__.
You may need to restart your kernel if you are running it in a notebook environment.
- Each quantum error present in the qiskit noise model is converted into an equivalent
:class:`~.QubitChannel` operator with the same canonical Kraus representation.
- Currently, PennyLane noise models do not support readout errors, so those will be skipped during
conversion.
**Example**
Consider the following noise model constructed in Qiskit:
>>> import qiskit_aer.noise as noise
>>> error_1 = noise.depolarizing_error(0.001, 1) # 1-qubit noise
>>> error_2 = noise.depolarizing_error(0.01, 2) # 2-qubit noise
>>> noise_model = noise.NoiseModel()
>>> noise_model.add_all_qubit_quantum_error(error_1, ['rz', 'ry'])
>>> noise_model.add_all_qubit_quantum_error(error_2, ['cx'])
This noise model can be converted into PennyLane using:
>>> import pennylane as qml
>>> qml.from_qiskit_noise(noise_model)
NoiseModel({
OpIn(['RZ', 'RY']): QubitChannel(num_kraus=4, num_wires=1)
OpIn(['CNOT']): QubitChannel(num_kraus=16, num_wires=2)
})
"""
try:
plugin_converter = plugin_converters["qiskit_noise"].load()
return plugin_converter(noise_model, verbose=verbose, decimal_places=decimal_places)
except KeyError as e:
raise RuntimeError(_MISSING_QISKIT_PLUGIN_MESSAGE) from e
[docs]
def from_qasm(quantum_circuit: str, measurements=None):
r"""
Loads quantum circuits from a QASM string using the converter in the
PennyLane-Qiskit plugin.
.. warning::
``from_qasm`` returns a **quantum function** that must be called.
.. code-block:: python
# INCORRECT: no operations will end up in the circuit
@qml.qnode(dev)
def circuit_from_qasm():
qml.from_qasm(qasm_string)
return qml.probs()
# CORRECT: from_qasm is called
@qml.qnode(dev)
def circuit_from_qasm():
qml.from_qasm(qasm_string)()
return qml.probs()
Args:
quantum_circuit (str): a QASM string containing a valid quantum circuit
measurements (None | MeasurementProcess | list[MeasurementProcess]): an optional PennyLane
measurement or list of PennyLane measurements that overrides the terminal measurements
that may be present in the input circuit. Defaults to ``None``, such that all existing measurements
in the input circuit are returned. See *Removing terminal measurements* for details.
Returns:
function: the PennyLane quantum function created based on the QASM string. This function itself returns the
mid-circuit measurements plus the terminal measurements by default (``measurements=None``),
and returns **only** the measurements from the ``measurements`` argument otherwise.
.. seealso:: :func:`~.from_qasm3`, which relies on the ``openqasm3`` and ``openqasm3[parser]`` packages
instead of ``pennylane-qiskit``, and supports newer syntax features.
**Example:**
.. code-block:: python
qasm_code = 'OPENQASM 2.0;' \
'include "qelib1.inc";' \
'qreg q[2];' \
'creg c[2];' \
'h q[0];' \
'measure q[0] -> c[0];' \
'rz(0.24) q[0];' \
'cx q[0], q[1];' \
'measure q -> c;'
loaded_circuit = qml.from_qasm(qasm_code)
>>> print(qml.draw(loaded_circuit)())
0: ──H──┤↗├──RZ(0.24)─╭●──┤↗├─┤
1: ───────────────────╰X──┤↗├─┤
Calling the quantum function returns a tuple containing the mid-circuit measurements and the terminal measurements.
>>> loaded_circuit()
(MeasurementValue(wires=[0]),
MeasurementValue(wires=[0]),
MeasurementValue(wires=[1]))
A list of measurements can also be passed directly to ``from_qasm`` using the ``measurements`` argument, making
it possible to create a PennyLane circuit with :class:`qml.QNode <pennylane.QNode>`.
.. code-block:: python
dev = qml.device("default.qubit")
measurements = [qml.var(qml.Y(0))]
circuit = qml.QNode(qml.from_qasm(qasm_code, measurements = measurements), dev)
>>> print(qml.draw(circuit)())
0: ──H──┤↗├──RZ(0.24)─╭●─┤ Var[Y]
1: ───────────────────╰X─┤
.. details::
:title: Removing terminal measurements
To remove all terminal measurements, set ``measurements=[]``. This removes the existing terminal
measurements and keeps the mid-circuit measurements.
.. code-block:: python
loaded_circuit = qml.from_qasm(qasm_code, measurements=[])
>>> print(qml.draw(loaded_circuit)())
0: ──H──┤↗├──RZ(0.24)─╭●─┤
1: ───────────────────╰X─┤
Calling the quantum function returns the same empty list that we originally passed in.
>>> loaded_circuit()
[]
Note that mid-circuit measurements are always applied, but are only returned when
``measurements=None``. This can be exemplified by using the ``loaded_circuit``
without the terminal measurements within a ``QNode``.
.. code-block:: python
dev = qml.device("default.qubit")
@qml.qnode(dev)
def circuit():
loaded_circuit()
return qml.expval(qml.Z(1))
>>> print(qml.draw(circuit)())
0: ──H──┤↗├──RZ(0.24)─╭●─┤
1: ───────────────────╰X─┤ <Z>
.. details::
:title: Using conditional operations
We can take advantage of the mid-circuit measurements inside the QASM code by
calling the returned function within a :class:`qml.QNode <pennylane.QNode>`.
.. code-block:: python
loaded_circuit = qml.from_qasm(qasm_code)
@qml.qnode(dev)
def circuit():
mid_measure, *_ = loaded_circuit()
qml.cond(mid_measure == 0, qml.RX)(np.pi / 2, 0)
return [qml.expval(qml.Z(0))]
>>> print(qml.draw(circuit)())
0: ──H──┤↗├──RZ(0.24)─╭●──┤↗├──RX(1.57)─┤ <Z>
1: ──────║────────────╰X──┤↗├──║────────┤
╚═════════════════════╝
.. details::
:title: Importing from a QASM file
We can also load the contents of a QASM file.
.. code-block:: python
# save the qasm code in a file
import locale
from pathlib import Path
filename = "circuit.qasm"
with Path(filename).open("w", encoding=locale.getpreferredencoding(False)) as f:
f.write(qasm_code)
with open("circuit.qasm", "r") as f:
loaded_circuit = qml.from_qasm(f.read())
The ``loaded_circuit`` function can now be used within a
:class:`qml.QNode <pennylane.QNode>` as a two-wire quantum template.
.. code-block:: python
@qml.qnode(dev)
def circuit(x):
qml.RX(x, wires=1)
loaded_circuit(wires=(0, 1))
return qml.expval(qml.Z(0))
>>> print(qml.draw(circuit)(1.23))
0: ──H─────────┤↗├──RZ(0.24)─╭●──┤↗├─┤ <Z>
1: ──RX(1.23)────────────────╰X──┤↗├─┤
"""
try:
plugin_converter = plugin_converters["qasm"].load()
except Exception as e: # pragma: no cover
raise RuntimeError( # pragma: no cover
"Failed to load the qasm plugin. Please ensure that the pennylane-qiskit package is installed."
) from e
return plugin_converter(quantum_circuit, measurements=measurements)
[docs]
def from_pyquil(pyquil_program):
"""Loads pyQuil Program objects by using the converter in the
PennyLane-Rigetti plugin.
**Example:**
>>> program = pyquil.Program()
>>> program += pyquil.gates.H(0)
>>> program += pyquil.gates.CNOT(0, 1)
>>> my_circuit = qml.from_pyquil(program)
The ``my_circuit`` template can now be used within QNodes, as a
two-wire quantum template.
>>> @qml.qnode(dev)
>>> def circuit(x):
>>> qml.RX(x, wires=1)
>>> my_circuit(wires=[1, 0])
>>> return qml.expval(qml.Z(0))
Args:
pyquil_program (pyquil.Program): a program created in pyQuil
Returns:
pennylane_forest.ProgramLoader: a ``pennylane_forest.ProgramLoader`` instance that can
be used like a PennyLane template and that contains additional inspection properties
"""
plugin_converter = plugin_converters["pyquil_program"].load()
return plugin_converter(pyquil_program)
[docs]
def from_quil(quil: str):
"""Loads quantum circuits from a Quil string using the converter in the
PennyLane-Rigetti plugin.
**Example:**
.. code-block:: python
quil_str = 'H 0\\nCNOT 0 1'
my_circuit = qml.from_quil(quil_str)
The ``my_circuit`` template can now be used within QNodes, as a
two-wire quantum template.
.. code-block:: python
@qml.qnode(dev)
def circuit(x):
qml.RX(x, wires=1)
my_circuit(wires=(1, 0))
return qml.expval(qml.Z(0))
Args:
quil (str): a Quil string containing a valid quantum circuit
Returns:
pennylane_forest.ProgramLoader: a ``pennylane_forest.ProgramLoader`` instance that can
be used like a PennyLane template and that contains additional inspection properties
"""
plugin_converter = plugin_converters["quil"].load()
return plugin_converter(quil)
[docs]
def from_quil_file(quil_filename: str):
"""Loads quantum circuits from a Quil file using the converter in the
PennyLane-Rigetti plugin.
**Example:**
>>> my_circuit = qml.from_quil_file("teleportation.quil")
The ``my_circuit`` template can now be used within QNodes, as a
two-wire quantum template.
>>> @qml.qnode(dev)
>>> def circuit(x):
>>> qml.RX(x, wires=1)
>>> my_circuit(wires=(1, 0))
>>> return qml.expval(qml.Z(0))
Args:
quil_filename (str): path to a Quil file containing a valid quantum circuit
Returns:
pennylane_forest.ProgramLoader: a ``pennylane_forest.ProgramLoader`` instance that can
be used like a PennyLane template and that contains additional inspection properties
"""
plugin_converter = plugin_converters["quil_file"].load()
return plugin_converter(quil_filename)
[docs]
def from_qasm3(quantum_circuit: str, wire_map: dict | None = None) -> Callable:
"""
Converts an OpenQASM 3.0 circuit into a quantum function that can be used within a QNode.
.. note::
The standard library gates, qubit registers, built-in mathematical functions and constants, subroutines,
variables, control flow, measurements, inputs, outputs, custom gates and ``end`` statements are all supported.
Pulses are not yet supported.
In order to use this function, ``openqasm3`` and ``'openqasm3[parser]'`` must be installed in the user's
environment. Please consult the `OpenQASM installation instructions <https://pypi.org/project/openqasm3>`__
for directions.
Args:
quantum_circuit (str): a QASM 3.0 string containing a simple quantum circuit.
wire_map (Optional[dict]): the mapping from OpenQASM 3.0 qubit names to PennyLane wires.
Returns:
Callable: A quantum function that will execute the program.
**Examples**
First, we define a QASM 3.0 circuit as a string. In this example, we define three qubits,
a few parameterized gates, a subroutine with a measurement, and a control flow statement.
.. code-block:: python
qasm_string = '''
qubit q0;
qubit q1;
qubit q2;
float theta = 0.2;
int power = 2;
ry(theta / 2) q0;
rx(theta) q1;
pow(power) @ x q0;
def random(qubit q) -> bit
{
bit b = "0";
h q;
measure q -> b;
return b;
}
bit m = random(q2);
if (m) {
int i = 0;
while (i < 5) {
i = i + 1;
rz(i) q1;
break;
}
}
'''
We can convert this circuit into a PennyLane quantum function using:
.. code-block:: python
@qml.qnode(qml.device("default.qubit", wires=[0, 1, 2]))
def my_circuit():
qml.from_qasm3(
qasm_string,
{'q0': 0, 'q1': 1, 'q2': 2}
)()
return qml.expval(qml.Z(0))
Inspecting the circuit, we can see that the operations and measurements have been correctly interpreted.
>>> print(qml.draw(my_circuit)())
0: ──RY(0.10)──X²────────────┤ <Z>
1: ──RX(0.20)───────RZ(1.00)─┤
2: ──H─────────┤↗├──║────────┤
╚═══╝
"""
if not has_openqasm: # pragma: no cover
raise ImportWarning(
"from_qasm3 requires openqasm3 and 'openqasm3[parser]' to be installed in your environment. "
"Please consult the OpenQASM 3.0 installation instructions for more information:"
" https://pypi.org/project/openqasm3/."
) # pragma: no cover
# parse the QASM program
try:
ast = openqasm3.parser.parse(quantum_circuit, permissive=True)
except AttributeError as e: # pragma: no cover
raise ImportError(
"antlr4-python3-runtime is required to interpret openqasm3 in addition to the openqasm3 package"
) from e # pragma: no cover
except Exception as e:
raise SyntaxError(
f"Something went wrong when parsing the provided OpenQASM 3.0 code. "
f"Please ensure the code is valid OpenQASM 3.0 syntax. {str(e)}",
) from e
def interpret_function(**kwargs):
context = QasmInterpreter().interpret(
ast, context={"name": "global", "wire_map": wire_map}, **kwargs
)
if context["return"]:
return tuple(map(lambda v: v.val, context["return"].values()))
return context
return interpret_function
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