# Source code for qiskit.providers.aer.library.set_instructions.set_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.
"""
Instruction to set the state simulator state to a matrix.
"""
from qiskit.circuit import QuantumCircuit, Instruction
from qiskit.extensions.exceptions import ExtensionError
from ..default_qubits import default_qubits
[docs]class SetMatrixProductState(Instruction):
"""Set the matrix product state of the simulator"""
_directive = True
def __init__(self, state):
"""Create new instruction to set the matrix product state of the simulator.
Args:
state (Tuple[List[Tuple[np.array[complex_t]]]], List[List[float]]):
A matrix_product_state.
.. note::
This set instruction must always be performed on the full width of
qubits in a circuit.
The matrix_product_state consists of a pair of vectors. The first is a
vector of pairs of matrices of complex numbers. The second is a vector of
vectors of double.
"""
super().__init__('set_matrix_product_state', len(state[0]), 0, [state])
[docs]def set_matrix_product_state(self, state):
"""Set the matrix product state of the simulator.
Args:
state (Tuple[List[Tuple[np.array[complex_t]]]], List[List[float]]):
A matrix_product_state.
Returns:
QuantumCircuit: with attached instruction.
Raises:
ExtensionError: If the structure of the state is incorrect
.. note:
This instruction is always defined across all qubits in a circuit.
"""
qubits = default_qubits(self)
if not isinstance(state, tuple) or len(state) != 2:
raise ExtensionError(
"The input matrix product state is not valid. Should be a list of 2 elements")
if not isinstance(state[0], list) or not isinstance(state[1], list):
raise ExtensionError(
"The first element of the input matrix product state is not valid. Should be a list.")
if len(state[0]) != len(state[1]) + 1:
raise ExtensionError(
"The input matrix product state is not valid. "
"Length of q_reg vector should be 1 more than length of lambda_reg")
for elem in state[0]:
if not isinstance(elem, tuple) or len(elem) != 2:
raise ExtensionError(
"The input matrix product state is not valid."
"The first element should be a list of length 2")
return self.append(SetMatrixProductState(state), qubits)
QuantumCircuit.set_matrix_product_state = set_matrix_product_state
```