import logging
import pandas as pd
import netsquid as ns
from utils import flush_port
from data_collection import collect_fidelity_data
from netsquid.protocols import NodeProtocol, Protocol, Signals
from qpu_programs import (
EmitProgram,
XCorrection,
YCorrection,
SwapProgram,
EPLDistillationProgram,
)
[docs]
class EntanglementProtocol(NodeProtocol):
"""
Protocol for establishing entanglement between two quantum network nodes.
This protocol runs on a `source` node and attempts to establish an entangled
Bell pair with the `target` node. Optionally, it applies local correction
operations based on the Bell state received from the control node.
Parameters
----------
source : netsquid.nodes.Node
Node running the protocol and emitting photons.
target : netsquid.nodes.Node
Destination node intended for entanglement.
ctrl_node : ControlNode
Central control node managing entanglement routing and corrections.
timeout : int
Maximum waiting time (in simulation time units) before aborting.
perform_correction : bool
Whether to apply local Pauli corrections after entanglement.
protocol_log : str
Protocol identifier string for logging purposes.
Examples
--------
>>> from simulation import setup_simple_network
>>> _, ctrl_node, [qnode_1, qnode_2] = setup_simple_network(
... dampening_parameter=0.1,
... routing={"qin0": "qout0", "qin1": "qout1", "qin2": "qout2"},
... ideal_switch=False,
... ideal_qpu=False,
... visibility=0.9
... ) # Setup network
>>> entanglement_protocol = EntanglementProtocol(
... ctrl_node=ctrl_node,
... source=qnode_1,
... target=qnode_2,
... timeout=400,
... perform_correction=True,
... ) # Setup entanglement protocol
>>> entanglement_protocol.start() # Run protocol
"""
def __init__(
self, ctrl_node, source, target, timeout=1500, perform_correction=True
):
super().__init__(source)
# Entanglement source (node which runs protocol) and target
self.source = source
self.target = target
self.ctrl_node = ctrl_node
self.timeout = timeout
self.perform_correction = perform_correction
self.protocol_log = "EBIT_CORRECT" if perform_correction else "EBIT_PASSIVE"
# Fetch logger
self.__logger = logging.getLogger("proto_logger")
[docs]
def run(self):
# Local vars
node_name = self.source.name
node_proc = self.source.processor
emit_idx = self.source.emit_idx
comm_idx = self.source.comm_idx
# Flush any stale messages on the corrections port
self.__logger.debug(
f"[{self.protocol_log}] {node_name}: Flushing corrections port."
)
flush_port(self.source.ports["corrections"])
# Execute the emit program
emit_photon = EmitProgram()
node_proc.execute_program(emit_photon, qubit_mapping=[comm_idx, emit_idx])
# Prepare to wait for the emit program to finish AND a port input, OR a timeout
emit_done = self.await_program(node_proc)
port_event = self.await_port_input(self.source.ports["corrections"])
timeout_event = self.await_timer(self.timeout)
compound_expr = emit_done & (port_event | timeout_event)
ent_expr = yield compound_expr
self.__logger.info("Emit program completed")
# Check if a timeout occurred.
if ent_expr.second_term.second_term.value:
self.__logger.info(
f"[{self.protocol_log}] {node_name} ebit establishment timeout."
)
return {"log": "timeout", "success": False}
# Process the Bell state from the received message
msg = self.source.ports["corrections"].rx_input()
if msg is None:
self.__logger.info(f"[{self.protocol_log}] {node_name} missing message")
return {"log": "no_msg", "success": False}
bell_state = msg.items[0].bell_index
if bell_state == -1:
self.__logger.info(
f"[{self.protocol_log}] {node_name} invalid entanglement"
)
result = {"log": "no entanglement", "success": False}
elif bell_state == 1:
self.__logger.info(
f"[{self.protocol_log}] {node_name} processing Bell state 1"
)
if self.perform_correction:
x_prog = XCorrection()
node_proc.execute_program(x_prog, qubit_mapping=[comm_idx])
yield self.await_program(node_proc)
result = {"log": "corrected", "success": True}
elif bell_state == 2:
self.__logger.info(
f"[{self.protocol_log}] {node_name} processing Bell state 2"
)
if self.perform_correction:
y_prog = YCorrection()
node_proc.execute_program(y_prog, qubit_mapping=[comm_idx])
yield self.await_program(node_proc)
result = {"log": "corrected", "success": True}
else:
self.__logger.error(
f"[{self.protocol_log}] {node_name} bad state: {bell_state}"
)
result = {"log": f"bad state: {bell_state}", "success": False}
return result
[docs]
class EntanglementRetryProto(Protocol):
"""
A higher-level protocol that retries entanglement attempts until success
or until reaching a maximum attempt limit.
This wrapper manages two `EntanglementProtocol` instances (one per node)
and coordinates retries across both until a valid Bell pair is established.
Parameters
----------
routing_table : dict
Placeholder routing table for entanglement setup (not yet used).
max_attempts : int
Maximum number of entanglement attempts.
timeout : int
Timeout per entanglement attempt (ns).
attempts : int
Number of entanglement attempts the protocol performs before giving up.
qnode_1 : netsquid.nodes.Node
First node in the entanglement attempt.
qnode_2 : netsquid.nodes.Node
Second node in the entanglement attempt.
subprotocol_qnode_1 : EntanglementProtocol
Entanglement protocol instance running on `qnode_1`.
subprotocol_qnode_2 : EntanglementProtocol
Entanglement protocol instance running on `qnode_2`.
"""
def __init__(
self,
ctrl_node,
qnode_1,
qnode_2,
routing_table,
max_attempts=10,
timeout=1500,
):
super().__init__()
self.routing_table = routing_table
self.max_attempts = max_attempts
self.timeout = timeout
self.attempts = 0
# Save nodes TODO remove when CTRL node switching is fixed
self.qnode_1 = qnode_1
self.qnode_2 = qnode_2
# Fetch logger
self.__logger = logging.getLogger("proto_logger")
# Create a single instance of the EntanglementProtocol
self.subprotocol_qnode_1 = EntanglementProtocol(
ctrl_node=ctrl_node,
source=qnode_1,
target=qnode_2,
timeout=timeout,
perform_correction=True,
)
self.subprotocol_qnode_2 = EntanglementProtocol(
ctrl_node=ctrl_node,
source=qnode_2,
target=qnode_1,
timeout=timeout,
perform_correction=False,
)
# Add the subprotocols
self.add_subprotocol(
self.subprotocol_qnode_1, name="qnode_1_entanglement_protocol"
)
self.add_subprotocol(
self.subprotocol_qnode_2, name="qnode_2_entanglement_protocol"
)
[docs]
def run(self):
for attempt in range(self.max_attempts):
# Register and log the attempt count
self.__logger.info(f"[RETRYPROTO] Attempt {attempt + 1}")
# Run the subprotocols and process the results.
self.subprotocol_qnode_1.reset()
self.subprotocol_qnode_2.reset()
self.start_subprotocols()
# Wait for finish signals from both subprotocols
yield self.await_signal(
self.subprotocol_qnode_1, signal_label=Signals.FINISHED
) & self.await_signal(
self.subprotocol_qnode_2, signal_label=Signals.FINISHED
)
# Retrieve results from subprotocols
qnode_1_result = self.subprotocol_qnode_1.get_signal_result(
Signals.FINISHED
)
qnode_2_result = self.subprotocol_qnode_2.get_signal_result(
Signals.FINISHED
)
self.__logger.info(
f"""[RETRYPROTO] Done
qnode_1: {qnode_1_result['log']}
qnode_2: {qnode_2_result['log']}"""
)
# Verify protocol response status
if qnode_1_result["success"] and qnode_2_result["success"]:
self.attempts = attempt + 1
return True
else:
self.__logger.debug("[RETRYPROTO] Failed, retrying")
# If all attempts fail return False
self.attempts = self.max_attempts
return False
[docs]
class ContinuousDistillationProtocol(Protocol):
"""
Continuous entanglement distillation protocol.
This protocol repeatedly attempts to establish entanglement between two
quantum nodes, performs qubit swapping, and applies entanglement purification
(EPL-style distillation) in multiple rounds. The goal is to iteratively
improve the fidelity of the shared entangled state.
Parameters
----------
ctrl_node : Node
Control node responsible for managing routing and coordination.
qnode_1 : Node
First quantum node participating in entanglement and distillation.
qnode_2 : Node
Second quantum node participating in entanglement and distillation.
routing_table : dict
Table defining routing information for entanglement attempts.
max_attempts : int, optional
Maximum number of entanglement attempts per phase (default: 10).
timeout : int, optional
Timeout for entanglement attempts in nanoseconds (default: 1500).
max_distillations : int, optional
Maximum number of distillation iterations to perform (default: 3).
"""
def __init__(
self,
ctrl_node,
qnode_1,
qnode_2,
routing_table,
max_attempts=10,
timeout=1500,
max_distillations=3,
):
super().__init__()
self.ctrl_node = ctrl_node
self.qnode_1 = qnode_1
self.qnode_2 = qnode_2
self.routing_table = routing_table
self.max_attempts = max_attempts
self.timeout = timeout
self.max_distillations = max_distillations
self.attempts = 0
self.success = False
# Fetch logger
self.__logger = logging.getLogger("proto_logger")
# Initialize subprotocols
self._setup_subprotocols()
def _setup_subprotocols(self):
"""Set up the entanglement subprotocols for qnode_1 and qnode_2."""
self.subprotocol_qnode_1 = EntanglementProtocol(
ctrl_node=self.ctrl_node,
source=self.qnode_1,
target=self.qnode_2,
timeout=self.timeout,
perform_correction=True,
)
self.subprotocol_qnode_2 = EntanglementProtocol(
ctrl_node=self.ctrl_node,
source=self.qnode_2,
target=self.qnode_1,
timeout=self.timeout,
perform_correction=False,
)
self.add_subprotocol(
self.subprotocol_qnode_1, name="qnode_1_entanglement_protocol"
)
self.add_subprotocol(
self.subprotocol_qnode_2, name="qnode_2_entanglement_protocol"
)
[docs]
def run(self):
self.__logger.info("[ContinuousDistill] Running protocol.")
# Storage for metrics collection
metrics_list = []
# Perform initial entanglement
init_success = yield from self._establish_entanglement(
metrics_list, phase="initial"
)
if not init_success:
return False, pd.DataFrame(metrics_list)
# Swap qubits
yield from self._swap_qubits()
# Perform distillation iterations
for i in range(self.max_distillations):
# Establish entanglement for this iteration
iteration_success = yield from self._establish_entanglement(
metrics_list, phase=f"distillation_{i + 1}"
)
if not iteration_success:
return False, pd.DataFrame(metrics_list)
# Perform distillation
distillation_success = yield from self._perform_distillation(i)
if not distillation_success:
# TODO
return False, pd.DataFrame(metrics_list)
# All steps completed successfully
self.success = True
return True, pd.DataFrame(metrics_list)
def _establish_entanglement(self, metrics_list, phase):
"""
Establish entanglement between qnode_1 and qnode_2.
Parameters
----------
metrics_list : list
List to store collected metrics
phase : str
Protocol phase name
Returns
-------
bool
True if entanglement was successfully established
"""
phase_desc = (
"initial" if phase == "initial" else f"iteration {phase.split('_')[1]}"
)
self.__logger.info(f"[ContinuousDistill] {phase} entanglement establishment.")
for attempt in range(self.max_attempts):
self.__logger.info(
f"[ContinuousDistill] {phase_desc} entanglement attempt {attempt+1}"
)
# Track attempts
self.attempts += 1
# Reset and start subprotocols
self.subprotocol_qnode_1.reset()
self.subprotocol_qnode_2.reset()
# Create request UUID and request route from control node
request_uuid = self.ctrl_node.request_route(
self.qnode_1.name, self.qnode_2.name
)
if request_uuid is None:
self.__logger.error("[ContinuousDistill] CTRL node NACKs route request")
return False
# Set request UUIDs for both nodes and run entanglement protocol
self.qnode_1.set_emit_uuid(request_uuid)
self.qnode_2.set_emit_uuid(request_uuid)
self.start_subprotocols()
# Wait for subprotocols to finish
subprotocols_done = self.await_signal(
self.subprotocol_qnode_1, signal_label=Signals.FINISHED
) & self.await_signal(
self.subprotocol_qnode_2, signal_label=Signals.FINISHED
)
yield subprotocols_done
self.__logger.info("Subprotocols completed")
# Collect metrics
data_point = collect_fidelity_data(subprotocols_done)
data_point["qnode_1"] = self.qnode_1.name
data_point["qnode_2"] = self.qnode_2.name
data_point["phase"] = phase
data_point["attempt"] = attempt + 1
data_point["total_attempts"] = self.attempts
data_point["time"] = ns.sim_time()
metrics_list.append(data_point)
# Get results
qnode_1_result = self.subprotocol_qnode_1.get_signal_result(
Signals.FINISHED
)
qnode_2_result = self.subprotocol_qnode_2.get_signal_result(
Signals.FINISHED
)
self.__logger.info(
f"[ContinuousDistill] {phase_desc}, attempt {attempt + 1}: "
f"qnode_1: {qnode_1_result['log']} | qnode_2: {qnode_2_result['log']}"
)
# Check success
if qnode_1_result["success"] and qnode_2_result["success"]:
return True
self.__logger.debug(
f"[ContinuousDistill] {phase_desc} entanglement failed, retrying."
)
self.__logger.debug(
f"[ContinuousDistill] {phase_desc} entanglement failed after max attempts."
)
return False
def _swap_qubits(self):
"""Perform qubit swap operation on both nodes."""
self.__logger.info(
"[ContinuousDistill] Swapping qubits (positions 1->2) on both nodes."
)
# Create and execute swap programs
qnode_1_swap_prog = SwapProgram()
qnode_2_swap_prog = SwapProgram()
self.qnode_1.processor.execute_program(qnode_1_swap_prog, qubit_mapping=[1, 2])
self.qnode_2.processor.execute_program(qnode_2_swap_prog, qubit_mapping=[1, 2])
# Wait for programs to complete
yield self.await_program(self.qnode_1.processor) & self.await_program(
self.qnode_2.processor
)
self.__logger.info("[ContinuousDistill] Swap operations completed.")
def _perform_distillation(self, iteration):
"""
Perform EPL distillation for the given iteration.
Parameters
----------
iteration : int
Current distillation iteration (0-indexed)
Returns
-------
bool
True if distillation was successful
"""
iteration_num = iteration + 1
self.__logger.info(
f"[ContinuousDistill] Running distillation at iteration {iteration_num}"
)
# Create and execute distillation programs
qnode_1_distill = EPLDistillationProgram()
qnode_2_distill = EPLDistillationProgram()
self.qnode_1.processor.execute_program(qnode_1_distill, qubit_mapping=[1, 2])
self.qnode_2.processor.execute_program(qnode_2_distill, qubit_mapping=[1, 2])
# Wait for programs to complete
yield self.await_program(self.qnode_1.processor) & self.await_program(
self.qnode_2.processor
)
# Check measurement outcomes
qnode_1_meas = qnode_1_distill.output["m_target"][0]
qnode_2_meas = qnode_2_distill.output["m_target"][0]
self.__logger.info(
f"""[ContinuousDistill] Iteration {iteration_num} results:
qnode_1: {qnode_1_meas}, qnode_2: {qnode_2_meas}"""
)
# Success condition: both outcomes equal 1
if (qnode_1_meas, qnode_2_meas) != (1, 1):
# TODO fix failed distillation terminating protocol
self.__logger.debug(
f"[ContinuousDistill] Distillation iteration {iteration_num} failed"
)
return False
self.__logger.info(
f"[ContinuousDistill] Distillation iteration {iteration_num} succeess."
)
return True