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sampling.py
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sampling.py
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# 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.
from collections.abc import Mapping
from typing import Any, Optional, Sequence
import qiskit
from qiskit.providers import Job
from qiskit.providers.backend import Backend
from qiskit.result import Result
from quri_parts.backend import (
BackendError,
CompositeSamplingJob,
SamplingBackend,
SamplingCounts,
SamplingJob,
SamplingResult,
)
from quri_parts.circuit import NonParametricQuantumCircuit
from quri_parts.circuit.transpile import CircuitTranspiler
from quri_parts.qiskit.circuit import QiskitCircuitConverter, convert_circuit
from .saved_sampling import (
QiskitSavedDataSamplingJob,
QiskitSavedDataSamplingResult,
encode_saved_data_job_sequence_to_json,
)
from .utils import (
convert_qiskit_sampling_count_to_qp_sampling_count,
distribute_backend_shots,
get_backend_min_max_shot,
get_job_mapper_and_circuit_transpiler,
)
class QiskitSamplingResult(SamplingResult):
"""A result of a Qiskit sampling job."""
def __init__(self, qiskit_result: Result):
if not isinstance(qiskit_result, Result):
raise ValueError("Only qiskit.result.Result is supported")
self._qiskit_result = qiskit_result
@property
def counts(self) -> SamplingCounts:
qiskit_counts = self._qiskit_result.get_counts()
return convert_qiskit_sampling_count_to_qp_sampling_count(qiskit_counts)
class QiskitSamplingJob(SamplingJob):
"""A job for a Qiskit sampling measurement."""
def __init__(self, qiskit_job: Job):
self._qiskit_job = qiskit_job
def result(self) -> SamplingResult:
qiskit_result: Result = self._qiskit_job.result()
return QiskitSamplingResult(qiskit_result)
class QiskitSamplingBackend(SamplingBackend):
"""A Qiskit backend for a sampling measurement.
Args:
backend: A Qiskit :class:`qiskit.providers.backend.Backend`
for circuit execution.
circuit_converter: A function converting
:class:`~quri_parts.circuit.NonParametricQuantumCircuit` to
a Qiskit :class:`qiskit.circuit.QuantumCircuit`.
circuit_transpiler: A transpiler applied to the circuit before running it.
:class:`~QiskitSetTranspiler` is used when not specified.
enable_shots_roundup: If True, when a number of shots specified to
:meth:`~sample` is smaller than the minimum number of shots supported by
the device, it is rounded up to the minimum. In this case, it is possible
that shots more than specified are used. If it is strictly not allowed to
exceed the specified shot count, set this argument to False.
qubit_mapping: If specified, indices of qubits in the circuit are remapped
before running it on the backend. It can be used when you want to use
specific backend qubits, e.g. those with high fidelity.
The mapping should be specified with "from" qubit
indices as keys and "to" qubit indices as values. For example, if
you want to map qubits 0, 1, 2, 3 to backend qubits as 0 → 4, 1 → 2,
2 → 5, 3 → 0, then the ``qubit_mapping`` should be
``{0: 4, 1: 2, 2: 5, 3: 0}``.
run_kwargs: Additional keyword arguments for
:meth:`qiskit.providers.backend.Backend.run` method.
save_data_while_sampling: If True, the circuit, n_shots and the
sampling counts will be saved. Please use the `.jobs` or `.jobs_json`
to access the saved data.
"""
def __init__(
self,
backend: Backend,
circuit_converter: QiskitCircuitConverter = convert_circuit,
circuit_transpiler: Optional[CircuitTranspiler] = None,
enable_shots_roundup: bool = True,
qubit_mapping: Optional[Mapping[int, int]] = None,
run_kwargs: Mapping[str, Any] = {},
save_data_while_sampling: bool = False,
):
self._backend = backend
# circuit related
self._circuit_converter = circuit_converter
(
self._job_mapper,
self._circuit_transpiler,
) = get_job_mapper_and_circuit_transpiler(qubit_mapping, circuit_transpiler)
# shots related
self._enable_shots_roundup = enable_shots_roundup
self._min_shots, self._max_shots = get_backend_min_max_shot(backend)
# other kwargs
self._run_kwargs = run_kwargs
# saving mode
self._save_data_while_sampling = save_data_while_sampling
self._saved_data: list[tuple[str, int, QiskitSamplingJob]] = []
def sample(self, circuit: NonParametricQuantumCircuit, n_shots: int) -> SamplingJob:
if not n_shots >= 1:
raise ValueError("n_shots should be a positive integer.")
shot_dist = distribute_backend_shots(
n_shots, self._min_shots, self._max_shots, self._enable_shots_roundup
)
qiskit_circuit = self._circuit_converter(circuit, self._circuit_transpiler)
qiskit_circuit.measure_all()
transpiled_circuit = qiskit.transpile(qiskit_circuit, self._backend)
circuit_qasm_str = transpiled_circuit.qasm()
jobs: list[QiskitSamplingJob] = []
try:
for s in shot_dist:
qiskit_job = self._backend.run(
transpiled_circuit,
shots=s,
**self._run_kwargs,
)
qiskit_sampling_job = QiskitSamplingJob(qiskit_job)
# Saving mode
if self._save_data_while_sampling:
self._saved_data.append((circuit_qasm_str, s, qiskit_sampling_job))
jobs.append(qiskit_sampling_job)
except Exception as e:
for qiskit_sampling_job in jobs:
try:
qiskit_sampling_job._qiskit_job.cancel()
except Exception:
# Ignore cancel errors
pass
raise BackendError("Qiskit Device.run failed.") from e
qubit_mapped_jobs = [self._job_mapper(job) for job in jobs]
return (
qubit_mapped_jobs[0]
if len(qubit_mapped_jobs) == 1
else CompositeSamplingJob(qubit_mapped_jobs)
)
@property
def jobs(self) -> Sequence[QiskitSavedDataSamplingJob]:
"""Convert saved data to a list of QiskitSavedDataSamplingJob
objects."""
job_list = []
for circuit_qasm_str, n_shots, qiskit_sampling_job in self._saved_data:
raw_measurement_cnt = qiskit_sampling_job._qiskit_job.result().get_counts()
saved_sampling_result = QiskitSavedDataSamplingResult(
raw_data=raw_measurement_cnt
)
saved_sampling_job = QiskitSavedDataSamplingJob(
circuit_qasm=circuit_qasm_str,
n_shots=n_shots,
saved_result=saved_sampling_result,
)
job_list.append(saved_sampling_job)
return job_list
@property
def jobs_json(self) -> str:
"""Encodes the list of QiskitSavedDataSamplingJob objects to a json
string."""
return encode_saved_data_job_sequence_to_json(self.jobs)