Noise

QDNS offers a transparent and fully customizable structure to simulate noise.

Noise Types

Noise patterns that QDNS can simulate:

import QDNS
print('channels = ', QDNS.noise_channels)

channels = (
    depolarisation_channel,
    bit_flip_channel,
    phase_flip_channel,
    bit_and_phase_flip_channel,
    reset_channel, no_noise_channel
)

As its name mentions, no noise channel does nothing.

Noise Locations

Noise is applied in many parts of the simulation.

State Prepair: This noise is applied right after qubit is allocated and resetted. Measure: This noise is applied before qubit is measured. Gate Error: This noise is applied immediately after any transformation. Scramble: This noise is applied when scramble is needed.

Also scramble method is applied qubits that passed quantum channel.

Default noise pattern is:

import QDNS
print(QDNS.default_noise_pattern)

State Prepair: bit_flip_channel | 0.005
Measure: bit_flip_channel | 0.005
Gate Error: phase_flip_channel | 0.005
Scramble Error: depolarisation | 0.577

Creating Noises

The following part of code explains how to change the noise pattern before simulation:

def main():
    ...
    net = QDNS.Network(...)
    conf = QDNS.BackendConfiguration(...)
    ...

    my_noise_pattern = QDNS.NoisePattern(
        0.05, 0.1, 0.2,
        sp_channel=QDNS.bit_flip_channel,
        measure_channel=QDNS.depolarisation_channel,
        gate_channel=QDNS.no_noise_channel,
        scramble_channel=QDNS.reset_channel
    )

    sim = QDNS.Simulator()
    sim.simulate(net, conf, noise_pattern=my_noise_pattern)

    # Or we can change default noise pattern before simulation too.
    # QDNS.change_default_noise_pattern(my_noise_pattern)

Quantum Channel Noise

QDNS uses 1680 nanometer Rayleigh scattering on fibre cable formula to calculate the error rate in channel. But this formula is can be changed easily before simulation:

def my_channel_error_calculator(length: float) -> [float 0 to 1]:
    ...
    ...
    ...
    return rate

def main():
    ...

    QDNS.change_default_altitude_formula(my_channel_error_calculator)
    sim = QDNS.Simulator()
    sim.simulate(...)