# Source code for qiskit.providers.aer.extensions.snapshot_stabilizer

# This code is part of Qiskit.
#
# (C) Copyright IBM 2018, 2019.
#
# 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 warnings import warn
from qiskit import QuantumCircuit
from .snapshot import Snapshot

[docs]class SnapshotStabilizer(Snapshot):
"""Snapshot instruction for stabilizer method of Qasm simulator."""

def __init__(self, label, num_qubits=0):
"""Create a stabilizer state snapshot instruction.

Args:
label (str): the snapshot label.
num_qubits (int): the instruction barrier size [Default: 0].

Raises:
ExtensionError: if snapshot is invalid.

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.

.. deprecated:: 0.9.0

This instruction has been deprecated and will be removed no earlier
than 3 months from the 0.9.0 release date. It has been superseded by the
:class:qiskit.providers.aer.library.SaveStabilizer instruction.
"""
warn('The SnapshotStabilizer instruction will be deprecated in the'
' future. It has been superseded by the save_stabilizer'
' instructions.', DeprecationWarning, stacklevel=2)
super().__init__(label, snapshot_type='stabilizer', num_qubits=num_qubits)

def snapshot_stabilizer(self, label):
"""Take a stabilizer 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.

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.

.. deprecated:: 0.9.0

This instruction has been deprecated and will be removed no earlier
than 3 months from the 0.9.0 release date. It has been superseded by the
:func:qiskit.providers.aer.library.save_stabilizer circuit
method.
"""
warn('The snapshot_stabilizer circuit method has been deprecated as of'
' qiskit-aer 0.9 and will be removed in a future release.'
' It has been superseded by the save_stabilizer'
' circuit method.', DeprecationWarning, stacklevel=2)
snapshot_register = Snapshot.define_snapshot_register(self)

return self.append(
SnapshotStabilizer(label, num_qubits=len(snapshot_register)),
snapshot_register)

QuantumCircuit.snapshot_stabilizer = snapshot_stabilizer