# Source code for qiskit.transpiler.passes.optimization.remove_reset_in_zero_state

# This code is part of Qiskit.
#
# (C) Copyright IBM 2017, 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.

"""Remove reset gate when the qubit is in zero state."""

from qiskit.circuit import Reset
from qiskit.transpiler.basepasses import TransformationPass

[docs]class RemoveResetInZeroState(TransformationPass):
"""Remove reset gate when the qubit is in zero state."""

[docs]    def run(self, dag):
"""Run the RemoveResetInZeroState pass on dag.

Args:
dag (DAGCircuit): the DAG to be optimized.

Returns:
DAGCircuit: the optimized DAG.
"""
resets = dag.op_nodes(Reset)
for reset in resets:
predecessor = next(dag.predecessors(reset))
if predecessor.type == 'in':
dag.remove_op_node(reset)
return dag