# SimQN: a discrete-event simulator for the quantum networks
# Copyright (C) 2021-2022 Lutong Chen, Jian Li, Kaiping Xue
# University of Science and Technology of China, USTC.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
from typing import Optional
from qns.models.core.backend import QuantumModel
from qns.models.epr.entanglement import BaseEntanglement
from qns.utils.rnd import get_rand
[docs]class BellStateEntanglement(BaseEntanglement, QuantumModel):
"""
`BellStateEntanglement` is the ideal max entangled qubits. Its fidelity is always 1.
"""
def __init__(self, fidelity: float = 1, name: Optional[str] = None, p_swap: float = 1):
super().__init__(fidelity=1, name=name)
self.p_swap = p_swap
[docs] def swapping(self, epr: "BellStateEntanglement"):
ne = BellStateEntanglement()
if self.is_decoherenced or epr.is_decoherenced:
ne.is_decoherenced = True
ne.fidelity = 0
r = get_rand()
if r > min(self.p_swap, epr.p_swap):
ne.is_decoherenced = True
ne.fidelity = 0
epr.is_decoherenced = True
self.is_decoherenced = True
return ne
[docs] def distillation(self, epr: "BellStateEntanglement"):
ne = BellStateEntanglement()
if self.is_decoherenced or epr.is_decoherenced:
ne.is_decoherenced = True
ne.fidelity = 0
epr.is_decoherenced = True
self.is_decoherenced = True
return ne
[docs] def store_error_model(self, t: Optional[float] = 0, decoherence_rate: Optional[float] = 0, **kwargs):
"""
The default error model for storing this entangled pair in a quantum memory.
The default behavior is doing nothing
Args:
t: the time stored in a quantum memory. The unit it second.
decoherence_rate (float): the decoherence_rate
kwargs: other parameters
"""
pass
[docs] def transfer_error_model(self, length: float, decoherence_rate: Optional[float] = 0, **kwargs):
"""
The default error model for transmitting this entanglement.
The default behavior is doing nothing
Args:
length (float): the length of the channel
decoherence_rate (float): the decoherency rate
kwargs: other parameters
"""
pass