Mach-Zehnder_photons_animation.gif
Summary
Description Mach-Zehnder photons animation.gif |
English:
Animation of
photons
in a
Mach–Zehnder interferometer
. In the empty interferometer each photon
interferes
with itself. If a detector is placed in the interferometer, the wavefunction will
collapse
so that the photon is either detected directly or it will move on and split at the second
beam splitter
without interference.
|
Date | |
Source | Own work |
Author | user:Geek3 |
This plot was created with
Matplotlib
.
Source Code
The image is created by the following python source-code. Requirements:
- python
- Matplotlib plotting library
Python Matplotlib source code |
---|
#!/usr/bin/python
# -*- coding: utf8 -*-
from math import *
import matplotlib.pyplot as plt
from matplotlib.patches import Polygon, Circle, Wedge
from matplotlib import animation
import numpy as np
# settings
fname = 'Mach-Zehnder_photons_animation'
width, height = 300, 220
nframes = 100
nphotons = 12
fps = 15
x0 = 100.5
x1 = 218.5
y0 = 200.5
y1 = 80.5
lx, lw, lh = 5, 46, 21 # laser
dtect = 62.5
t1, t2, tmove = 0.25, 0.9, 0.025
ymove = 24
rp = 2. # photon radius
cp1 = '#ff0000' # photon color
cp2 = '#ffaaaa' # splitphoton color
##
xstart = lx + lw / 2.
dx = x1 - x0
dy = y1 - y0
l = (x0 - xstart) + abs(dx) + abs(dy) + dtect + 2.*rp
xdet0 = (x0 + x1) / 2
fly_frac = 0.7
v = l / fly_frac
tdet0 = (xdet0 + 2.*rp - xstart) / v
tdet12 = l / v
# introduce artificial antibunching for illustration purpose
ptimes = (np.random.random() + np.sort(np.random.random(3*nphotons))[::3]) % 1
photons = [{} for i in range(nphotons)]
for i, p in enumerate(photons):
p['t0'] = ptimes[i]
if t1 <= (p['t0'] + tdet0) % 1 and (p['t0'] + tdet0) % 1 <= t2:
# photon sees first detector
if np.random.randint(2) == 0:
# photon hits extra detector
p['arm'] = 'none'
p['det'] = 0
else:
# photon escapes first detector
p['arm'] = 'lower'
# => random detection at second beam splitter
if np.random.randint(2) == 0:
p['det'] = 1
else:
p['det'] = 2
else:
# photon sees standard Mach-Zehnder interferometer
p['arm'] = 'both'
p['det'] = 1
if p['det'] == 0:
p['tdet'] = (p['t0'] + tdet0) % 1
else:
p['tdet'] = (p['t0'] + tdet12) % 1
p['click_frame'] = int(round(p['tdet'] * nframes)) % nframes
plt.close('all')
mpl.rc('path', snap=False)
def animate(nframe):
# prepare a clean and image-filling canvas for each frame
plt.clf()
fig.gca().set_position((0, 0, 1, 1))
plt.xlim(0, width)
plt.ylim(0, height)
plt.axis('off')
t = float(nframe) / nframes
# photons
for p in photons:
s0 = v * ((t - p['t0']) % 1)
if s0 > l:
continue
s = s0 + start - x0
if s <= 0:
# from laser to first beam splitter
x, y = x0 + s, y0
fig.gca().add_patch(Circle((x, y), rp, color=cp1))
elif s <= abs(dx) + abs(dy):
# in the interferometer
if s < abs(dx):
xu, yu = x0 + copysign(s, dx), y0
else:
xu, yu = x1, y0 + copysign(s - abs(dx), dy)
if s < abs(dy):
xd, yd = x0, y0 + copysign(s, dy)
else:
xd, yd = x0 + copysign(s - abs(dy), dx), y1
if s < xdet0 - x0 or p['arm'] == 'both':
fig.gca().add_patch(Circle((xu, yu), rp, color=cp2))
fig.gca().add_patch(Circle((xd, yd), rp, color=cp2))
elif p['arm'] == 'lower':
fig.gca().add_patch(Circle((xd, yd), rp, color=cp1))
else:
# after the interferometer
x, y = x1 + (s - abs(dx) - abs(dy)), y1
if p['arm'] == 'both':
fig.gca().add_patch(Circle((x, y), rp, color=cp1))
elif p['arm'] == 'lower':
fig.gca().add_patch(Circle((x, y), rp, color=cp2))
x, y = x1, y1 - (s - abs(dx) - abs(dy))
fig.gca().add_patch(Circle((x, y), rp, color=cp2))
# laser
fig.gca().add_patch(
Polygon([[lx, y0-lh/2.], [lx, y0+lh/2.],
[lx+lw, y0+lh/2.], [lx+lw, y0-lh/2.]],
closed=True, facecolor='#cccccc', edgecolor='black'))
plt.text(lx+lw/2., y0-2, 'laser', fontsize=12,
horizontalalignment='center', verticalalignment='center')
# beam splitters
b = 12
fig.gca().add_patch(
Polygon([[x0-b, y0+b], [x0+b, y0+b], [x0+b, y0-b],
[x0-b, y0-b], [x0-b, y0+b], [x0+b, y0-b]],
closed=True, facecolor='#88aadd', edgecolor='black',
linewidth=2, alpha=0.4))
fig.gca().add_patch(
Polygon([[x1-b, y1+b], [x1+b, y1+b], [x1+b, y1-b],
[x1-b, y1-b], [x1-b, y1+b], [x1+b, y1-b]],
closed=True, facecolor='#88aadd', edgecolor='black',
linewidth=2, alpha=0.4))
# mirrors
m, mw = 12, 4
fig.gca().add_patch(
Polygon([[x1-m+mw/2., y0+m+mw/2.], [x1+m+mw/2., y0-m+mw/2.]],
closed=False, edgecolor='#555555', linewidth=mw))
fig.gca().add_patch(
Polygon([[x0-m-mw/2., y1+m-mw/2.], [x0+m-mw/2., y1-m-mw/2.]],
closed=False, edgecolor='#555555', linewidth=mw))
# detectors
c_off = '#cccccc'
c_on = '#cc0000'
c0 = c1 = c2 = c_off
for p in photons:
if p['click_frame'] == nframe:
if p['det'] == 0: c0 = c_on
if p['det'] == 1: c1 = c_on
if p['det'] == 2: c2 = c_on
if t1 <= t and t <= t2:
yd = y0
else:
yd = y0 - min((t1-t)%1, tmove, (t-t2)%1) * ymove / float(tmove)
fig.gca().add_patch(mpl.patches.Wedge((xdet0, yd), b, 270, 90, fc=c0))
fig.gca().add_patch(mpl.patches.Wedge((x1 + dtect, y1), b, 270, 90, fc=c1))
fig.gca().add_patch(mpl.patches.Wedge((x1, y1 - dtect), b, 180, 0, fc=c2))
fig = plt.figure(figsize=(width/100., height/100.))
anim = animation.FuncAnimation(fig, animate, frames=nframes)
anim.save(fname + '.gif', writer='imagemagick', fps=fps)
|
Postprocessing with gifsicle :
gifsicle -k 64 --background="#ffffff" -O3 --careful -i < Mach-Zehnder_photons_animation.gif > Mach-Zehnder_photons_animation_.gif
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