# 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 SnapshotStatevector(Snapshot):
""" Snapshot instruction for statevector snapshot type """
def __init__(self, label, num_qubits=0):
"""Create a statevector state snapshot instruction.
Args:
label (str): the snapshot label.
num_qubits (int): the instruction barrier size [Default: 0].
Raises:
ExtensionError: if snapshot is invalid.
Additional Information:
This snapshot is always performed on all qubits in a circuit.
The number of qubits parameter specifies the size of the
instruction as a barrier and should be set to the number of
qubits in the circuit.
"""
super().__init__(label, snapshot_type='statevector', num_qubits=num_qubits)
def snapshot_statevector(self, label):
"""Take a statevector snapshot of the simulator state.
Args:
label (str): a snapshot label to report the result.
Returns:
QuantumCircuit: with attached instruction.
Raises:
ExtensionError: if snapshot is invalid.
Additional Information:
This snapshot is always performed on all qubits in a circuit.
The number of qubits parameter specifies the size of the
instruction as a barrier and should be set to the number of
qubits in the circuit.
"""
# Statevector snapshot acts as a barrier across all qubits in the
# circuit
snapshot_register = Snapshot.define_snapshot_register(self, label)
return self.append(
SnapshotStatevector(label, num_qubits=len(snapshot_register)),
snapshot_register)
QuantumCircuit.snapshot_statevector = snapshot_statevector