File:Wigner quasiprobability distribution of a coherent state.webm
Summary
Description |
English: Wigner quasiprobability distribution of a coherent state.
Matplotlibimport matplotlib.pyplot as plt
import matplotlib as mpl
import numpy as np
from IPython.display import display
from qutip import (about, basis, coherent, coherent_dm, displace, fock, ket2dm,
plot_wigner, squeeze, thermal_dm, wigner_cmap, wigner)
import scipy.ndimage
import os
from tqdm import tqdm
def rotate_and_crop(array, angle, xvec, yvec):
rotated_array = scipy.ndimage.rotate(array, -angle, reshape=False)
rows, cols = rotated_array.shape
center_row, center_col = rows // 2, cols // 2
target_rows, target_cols = len(yvec), len(xvec)
start_row = center_row - target_rows // 2
end_row = start_row + target_rows
start_col = center_col - target_cols // 2
end_col = start_col + target_cols
return rotated_array[start_row:end_row, start_col:end_col]
def plot_wigner_marginals(W, xvec, yvec, marginal_max, resolution=200, angle=0):
wmap = wigner_cmap(W)
wlim = np.abs(W).max()
cmap = plt.colormaps['RdBu']
fig = plt.figure()
n, m = 5, 1
fig, axes = plt.subplot_mosaic(
[ ["top"] * n + ["3d"] * m ] * m + [ ["mid"] * n + ["right"] * m] * n,
figsize=(20, 20),
layout="constrained",
width_ratios=[1.05] * (n+m))
ax = axes["mid"]
norm = mpl.colors.Normalize(-wlim, wlim)
ax.contourf(xvec, yvec, W, resolution // 3, norm=norm, cmap=cmap)
ax = axes["top"]
x_marginal = np.sum(W, axis=0)
y_marginal = np.sum(W, axis=1)
ax.fill_between(xvec, x_marginal, 0, color='#938fba', alpha=0.5)
ax.plot(xvec, x_marginal, color='#4a5a90')
ax.set_xlim(min(xvec), max(xvec))
ax.set_ylim(0, marginal_max * 1.05)
ax.set_xticks([])
ax.set_yticks([])
ax = axes["right"]
ax.fill_betweenx(yvec, np.sum(W, axis=1), 0, color='#938fba', alpha=0.5)
ax.plot(y_marginal, yvec, color='#4a5a90')
ax.set_xlim(0, marginal_max * 1.05)
ax.set_ylim(min(yvec), max(yvec))
ax.set_xticks([])
ax.set_yticks([])
ax = axes["3d"]
ax.axis('off')
return fig
def plot_wigner_with_marginals(psi, **kwargs):
radius = kwargs.get('radius', 5)
resolution = kwargs.get('resolution', 500)
angles = kwargs.get('angles', np.linspace(0, 2*np.pi, 100))
dir_path = kwargs.get('dir_path', './output')
xvec_upscaled = np.linspace(-radius*1.5, radius*1.5, int(resolution*1.5))
yvec_upscaled = np.linspace(-radius*1.5, radius*1.5, int(resolution*1.5))
xvec = np.linspace(-radius, radius, int(resolution))
yvec = np.linspace(-radius, radius, int(resolution))
W_upscaled = wigner(psi, xvec_upscaled, yvec_upscaled)
marginal_max = max(max(np.sum(W_upscaled, axis=0)), max(np.sum(W_upscaled, axis=1)))
print(f"outputting to {dir_path}")
for N, angle in tqdm(enumerate(angles)):
W = rotate_and_crop(W_upscaled, angle, xvec, yvec)
fig = plot_wigner_marginals(W, xvec, yvec, marginal_max=marginal_max, resolution=resolution, angle=angle)
if not os.path.exists(dir_path):
os.makedirs(dir_path)
fig.savefig(f"{dir_path}/{N:03d}.png",bbox_inches='tight')
plt.close(fig)
mpl.use('agg')
configs = {
"N_dim" : 50,
"radius" : 4.5,
"resolution" : 600,
"angles" : [3 * i for i in range(120)],
"dir_path" : ""
}
for separation in [2]:
for cat_number in [1]:
psi = sum(
[coherent(configs["N_dim"], separation * np.exp(2j * np.pi * m / cat_number))
for m in range(cat_number)]
).unit()
configs["dir_path"] = f"./cat/cat_{cat_number}_{separation:.1f}"
plot_wigner_with_marginals(psi, **configs) |
Date | |
Source | Own work |
Author | Cosmia Nebula |
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