# Source code for qiskit.providers.aer.library.save_instructions.save_matrix_product_state

```
# This code is part of Qiskit.
#
# (C) Copyright IBM 2018, 2021.
#
# 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 instruction to save matrix product state.
"""
from qiskit.circuit import QuantumCircuit
from .save_data import SaveSingleData
from ..default_qubits import default_qubits
[docs]class SaveMatrixProductState(SaveSingleData):
"""Save matrix product state instruction"""
def __init__(self, num_qubits,
label="matrix_product_state",
pershot=False,
conditional=False):
"""Create new instruction to save the matrix product state.
Args:
num_qubits (int): the number of qubits
label (str): the key for retrieving saved data from results.
pershot (bool): if True save the mps for each
shot of the simulation [Default: False].
conditional (bool): if True save data conditional on the current
classical register values [Default: False].
.. note::
This save instruction must always be performed on the full width of
qubits in a circuit, otherwise an exception will be raised during
simulation.
"""
super().__init__('save_matrix_product_state',
num_qubits,
label,
pershot=pershot,
conditional=conditional)
[docs]def save_matrix_product_state(self, label="matrix_product_state", pershot=False, conditional=False):
"""Save the current simulator quantum state as a matrix product state.
Args:
label (str): the key for retrieving saved data from results.
pershot (bool): if True save the mps for each
shot of the simulation [Default: False].
conditional (bool): if True save pershot data conditional on the
current classical register values
[Default: False].
Returns:
QuantumCircuit: with attached instruction.
.. note:
This instruction is always defined across all qubits in a circuit.
"""
qubits = default_qubits(self)
instr = SaveMatrixProductState(len(qubits),
label=label,
pershot=pershot,
conditional=conditional)
return self.append(instr, qubits)
QuantumCircuit.save_matrix_product_state = save_matrix_product_state
```