# This code is part of Qiskit.
#
# (C) Copyright IBM 2018, 2019.
#
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
#
# Any modifications or derivative works of this code must retain this
# copyright notice, and modified files need to carry a notice indicating
# that they have been altered from the originals
"""
Simulator command to snapshot internal simulator representation.
"""
from qiskit import QuantumCircuit
from qiskit.providers.aer.extensions import Snapshot
[docs]class SnapshotProbabilities(Snapshot):
"""Snapshot instruction for all methods of Qasm simulator."""
def __init__(self, label, num_qubits, variance=False):
"""Create a probability snapshot instruction.
Args:
label (str): the snapshot label.
num_qubits (int): the number of qubits to snapshot.
variance (bool): compute variance of probabilities [Default: False]
Raises:
ExtensionError: if snapshot is invalid.
"""
snapshot_type = 'probabilities_with_variance' if variance else 'probabilities'
super().__init__(label, snapshot_type=snapshot_type,
num_qubits=num_qubits)
def snapshot_probabilities(self, label, qubits, variance=False):
"""Take a probability snapshot of the simulator state.
Args:
label (str): a snapshot label to report the result
qubits (list): the qubits to snapshot.
variance (bool): compute variance of probabilities [Default: False]
Returns:
QuantumCircuit: with attached instruction.
Raises:
ExtensionError: if snapshot is invalid.
"""
snapshot_register = Snapshot.define_snapshot_register(self, label, qubits)
return self.append(
SnapshotProbabilities(label,
num_qubits=len(snapshot_register),
variance=variance),
snapshot_register)
QuantumCircuit.snapshot_probabilities = snapshot_probabilities