Optical Channel

Models for simulation of optical fiber channels.

This module introduces the abstract OpticalChannel class for general optical fibers. It also defines the QuantumChannel class for transmission of qubits/photons and the ClassicalChannel class for transmission of classical control messages. OpticalChannels must be attached to nodes on both ends.

class sequence.components.optical_channel.ClassicalChannel(name: str, timeline: Timeline, distance: float, delay: int = -1)

Optical channel for transmission of classical messages.

Classical message transmission is assumed to be lossless.

name

label for channel instance.

Type:: str

timeline

timeline for simulation.

Type:: Timeline

sender

node at sending end of optical channel.

Type:: Node

receiver

name of the node at receiving end of optical channel.

Type:: str

distance

length of the fiber (in m).

Type:: float

delay

delay (in ps) of message transmission (default distance / light_speed).

Type:: float

set_ends(sender: Node, receiver: str) → None

Method to set endpoints for the classical channel.

This must be performed before transmission.

Parameters:

sender (Node) – node sending classical messages.
receiver (str) – name of node receiving classical messages.

transmit(message: Message, source: Node, priority: int) → None

Method to transmit classical messages.

Parameters:

message (Message) – message to be transmitted.
source (Node) – node sending the message.
priority (int) – priority of transmitted message (to resolve message reception conflicts).

Side Effects:: Receiver node may receive the qubit (via the receive_qubit method).

class sequence.components.optical_channel.OpticalChannel(name: str, timeline: Timeline, attenuation: float, distance: float, polarization_fidelity: float, light_speed: float)

Parent class for optical fibers.

name

label for channel instance.

Type:: str

timeline

timeline for simulation.

Type:: Timeline

sender

node at sending end of optical channel.

Type:: Node

receiver

name of the node at receiving end of optical channel.

Type:: str

attenuation

attenuation of the fiber (in dB/m).

Type:: float

distance

length of the fiber (in m).

Type:: float

polarization_fidelity

probability of no polarization error for a transmitted qubit.

Type:: float

light_speed

speed of light within the fiber (in m/ps).

Type:: float

init() → None

Method to initialize entity (abstract).

Entity init methods are invoked for all timeline entities when the timeline is initialized. This method can be used to perform any necessary functions before simulation.

class sequence.components.optical_channel.QuantumChannel(name: str, timeline: Timeline, attenuation: float, distance: float, polarization_fidelity: float = 1.0, light_speed: float = 0.0002, frequency: float = 80000000.0)

Optical channel for transmission of photons/qubits.

name

label for channel instance.

Type:: str

timeline

timeline for simulation.

Type:: Timeline

sender

node at sending end of optical channel.

Type:: Node

receiver

name of the node at receiving end of optical channel.

Type:: str

attenuation

attenuation of the fiber (in dB/m).

Type:: float

distance

length of the fiber (in m).

Type:: float

polarization_fidelity

probability of no polarization error for a transmitted qubit.

Type:: float

light_speed

speed of light within the fiber (in m/ps).

Type:: float

loss

loss rate for transmitted photons (determined by attenuation).

Type:: float

delay

delay (in ps) of photon transmission (determined by light speed, distance).

Type:: int

frequency

maximum frequency of qubit transmission (in Hz).

Type:: float

init() → None: Implementation of Entity interface (see base class).

schedule_transmit(min_time: int) → int

Method to schedule a time for photon transmission.

Quantum Channels are limited by a frequency of transmission. This method returns the next available time for transmitting a photon.

Parameters:: min_time (int) – minimum simulation time for transmission.
Returns:: simulation time for next available transmission window.
Return type:: int

set_ends(sender: Node, receiver: str) → None

Method to set endpoints for the quantum channel.

This must be performed before transmission.

Parameters:

sender (Node) – node sending qubits.
receiver (str) – name of node receiving qubits.

time_to_timebin(time: int, frequency: float) → int

Convert simulation time to time bin.: Use the gmpy2.mpfr for high precision floating points. The precision is set to 200 bits, equivalent to around 54 significant decimal digits. The float in Python is 64 bits, equivalent to around 16 significant decimal digits.

Parameters:

time (int) – simulation time (picoseconds) to convert.
frequency (float) – frequency of the channel.

Returns:

time bin corresponding to the given simulation time.

Return type:

int

timebin_to_time(time_bin: int, frequency: float) → int

Convert time bin to simulation time (picoseconds).: Use the gmpy2.mpz for high precision integers. Use the gmpy2.mpfr for high precision floating points.

Parameters:

time_bin (int) – time bin to convert.
frequency (float) – frequency of the channel.

Returns:

simulation time (picoseconds) corresponding to the given time bin.

Return type:

int

transmit(qubit: Photon, source: Node) → None

Method to transmit photon-encoded qubits.

Parameters:

qubit (Photon) – photon to be transmitted.
source (Node) – source node sending the qubit.

Side Effects:: Receiver node may receive the qubit (via the receive_qubit method).