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__init__.py
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__init__.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 typing import TYPE_CHECKING, Any, NamedTuple, Optional, Sequence
import stim
from quri_parts.core.estimator import (
ConcurrentQuantumEstimator,
Estimatable,
Estimate,
QuantumEstimator,
)
from quri_parts.core.operator import zero
from quri_parts.core.state.state import CircuitQuantumState
from quri_parts.core.utils.concurrent import execute_concurrently
from quri_parts.stim.circuit import convert_circuit
from ..operator import convert_operator
if TYPE_CHECKING:
from concurrent.futures import Executor
class _Estimate(NamedTuple):
value: complex
error: float = 0.0
def _estimate(operator: Estimatable, state: CircuitQuantumState) -> Estimate[complex]:
if operator == zero():
return _Estimate(value=0.0)
exp_val: complex = 0.0
qubit_count = state.qubit_count
sim = stim.TableauSimulator()
circuit = convert_circuit(state.circuit)
op_terms = convert_operator(operator, qubit_count)
sim.do_circuit(circuit)
generators = sim.canonical_stabilizers()
for p_string, coef in op_terms:
if not all(generator.commutes(p_string) for generator in generators):
continue
exp_val += coef * sim.peek_observable_expectation(p_string)
return _Estimate(value=exp_val)
def create_stim_clifford_estimator() -> QuantumEstimator[CircuitQuantumState]:
"""Returns a :class:`~QuantumEstimator` that uses stim's
:class:`TableauSimulator` to calculate expectation values."""
return _estimate
def _sequential_estimate(
_: Any, op_state_tuples: Sequence[tuple[Estimatable, CircuitQuantumState]]
) -> Sequence[Estimate[complex]]:
return [_estimate(operator, state) for operator, state in op_state_tuples]
def _sequential_estimate_single_state(
state: CircuitQuantumState, operators: Sequence[Estimatable]
) -> Sequence[Estimate[complex]]:
qubit_count = state.qubit_count
sim = stim.TableauSimulator()
circuit = convert_circuit(state.circuit)
sim.do_circuit(circuit)
generators = sim.canonical_stabilizers()
results = []
for op in operators:
stim_op = convert_operator(op, qubit_count)
exp_val: complex = 0.0
for p_string, coef in stim_op:
if not all(generator.commutes(p_string) for generator in generators):
continue
exp_val += coef * sim.peek_observable_expectation(p_string)
results.append(_Estimate(value=exp_val))
return results
def _concurrent_estimate(
operators: Sequence[Estimatable],
states: Sequence[CircuitQuantumState],
executor: Optional["Executor"],
concurrency: int = 1,
) -> Sequence[Estimate[complex]]:
num_ops = len(operators)
num_states = len(states)
if num_ops == 0:
raise ValueError("No operator specified.")
if num_states == 0:
raise ValueError("No state specified.")
if num_ops > 1 and num_states > 1 and num_ops != num_states:
raise ValueError(
f"Number of operators ({num_ops}) does not match"
f"number of states ({num_states})."
)
if num_states == 1:
return execute_concurrently(
_sequential_estimate_single_state,
next(iter(states)),
operators,
executor,
concurrency,
)
else:
if num_ops == 1:
operators = [next(iter(operators))] * num_states
return execute_concurrently(
_sequential_estimate, None, zip(operators, states), executor, concurrency
)
def create_stim_clifford_concurrent_estimator(
executor: Optional["Executor"] = None, concurrency: int = 1
) -> ConcurrentQuantumEstimator[CircuitQuantumState]:
"""Returns a :class:`~ConcurrentQuantumEstimator` that uses stim's
:class:`TableauSimulator` to calculate expectation values."""
def estimator(
operators: Sequence[Estimatable], states: Sequence[CircuitQuantumState]
) -> Sequence[Estimate[complex]]:
return _concurrent_estimate(operators, states, executor, concurrency)
return estimator