noise_models_kraus.py

import numpy as np
from pyquil.noise import damping_kraus_map, dephasing_kraus_map, damping_after_dephasing
# http://docs.rigetti.com/en/stable/apidocs/noise.html for descriptions of the above three functions

def bit_flip_channel(prob: float):
    noisy_I = np.sqrt(1-prob) * np.asarray([[1, 0], [0, 1]])
    noisy_X = np.sqrt(prob) * np.asarray([[0, 1], [1, 0]])
    return [noisy_I, noisy_X]


def phase_flip_channel(prob: float):
    noisy_I = np.sqrt(1-prob) * np.asarray([[1, 0], [0, 1]])
    noisy_Z = np.sqrt(prob) * np.asarray([[1, 0], [0, -1]])
    return [noisy_I, noisy_Z]


def depolarizing_channel(prob: float):
    noisy_I = np.sqrt(1-prob) * np.asarray([[1, 0], [0, 1]])
    noisy_X = np.sqrt(prob/3.0) * np.asarray([[0, 1], [1, 0]])    
    noisy_Y = 1j	* np.sqrt(prob/3.0) * np.asarray([[0, -1], [1, 0]])
    noisy_Z = np.sqrt(prob/3.0) * np.asarray([[1, 0], [0, -1]])
    return [noisy_I, noisy_X,noisy_Y, noisy_Z]
    
# Set pz = prob / 3 for unbiased depolarizing-channel
# Set pz = prob for phase-flip-channel
def biased_depolarizing_channel(prob: float, pz: float):  # px+py+pz=prob
    pxy = (prob - pz) / 2  # px=py=pxy
    eta = pz / (prob - pz)  # bias of Z errors
    noisy_I = np.sqrt(1-prob) * np.asarray([[1, 0], [0, 1]])
    noisy_X = np.sqrt(pxy) * np.asarray([[0, 1], [1, 0]])
    noisy_Y = np.sqrt(pxy) * np.asarray([[0, -1], [1, 0]]) * complex(0, 1)
    noisy_Z = np.sqrt(pz) * np.asarray([[1, 0], [0, -1]])
    return [noisy_I, noisy_X, noisy_Y, noisy_Z, eta]