(*Source code written in Mathematica 6.0 by Steve Byrnes, Apr. 2011.
  This source code is public domain.*)
  
(*Shows classical and quantum trajectory animations for an infinite-square-well potential.
  Assumes L=hbar=1, m=2*pi^(-2), so that the nth energy eigenstate has energy n^2.*)

ClearAll["Global`*"]

(***Wavefunctions of the energy eigenstates***)
psi[n_, x_] := Sin[n*Pi*x]*2^(1/2);
energy[n_] := n^2;
psit[n_, x_, t_] := psi[n, x] Exp[-I*energy[n]*t];

(***A random time-dependent state***)
SeedRandom[1];
CoefList = Table[Random[]*Exp[2*Pi*I*Random[]], {n, 1, 4}];
CoefList = CoefList/Norm[CoefList];
Randpsi[x_, t_] := Sum[CoefList[[n]]*psit[n, x, t], {n, 1, 4}];

(***Another random time-dependent state***)
SeedRandom[2];
CoefList2 = Table[Random[]*Exp[2*Pi*I*Random[]], {n, 1, 3}];
CoefList2 = CoefList2/Norm[CoefList2];
Randpsi2[x_, t_] := Sum[CoefList2[[n]]*psit[n, x, t], {n, 1, 3}];

(***Set default style for plots***)
SetOptions[Plot,
  {PlotRange -> {{-.05, 1.05}, {-2.5, 2.5}}, Ticks -> None, 
   PlotStyle -> {Directive[Thick, Blue], Directive[Thick, Pink]}, 
   Axes -> {True, False}}];
SetOptions[ListPlot, {PlotRange -> {{-.05, 1.05}, {-2.5, 2.5}}, Axes -> False}];

(***Draw walls***)
walls = ListPlot[{{{0, -2.5}, {0, 2.5}}, {{1, -2.5}, {1, 2.5}}}, 
   Joined -> True, PlotStyle -> {{Thick, Black}, {Thick, Black}}];

(***Make the classical plot...a red ball bounces back and forth.***)
classicaltrajectory[t_, left_, right_] := 2*(right - left)*Abs[t - Round[t]] + left;
classicalball[t_, left_, right_] := ListPlot[{{classicaltrajectory[t, left, right], 0}},
   PlotStyle -> Directive[Red, AbsolutePointSize[15]]];
classical[t_, label_] := Show[walls, classicalball[t, .1, .9], PlotLabel -> label];
(***Make the quantum plots***)
plotpsi[n_, t_, label_] := Show[walls,
   Plot[{Re[psit[n, x, t]], Im[psit[n, x, t]]}, {x, 0, 1}],
   PlotLabel -> label, Axes -> {True, False}, Ticks -> None];
plotrand[t_, label_] := Show[walls,
   Plot[{Re[Randpsi[x, t]], Im[Randpsi[x, t]]}, {x, 0, 1}],
   PlotLabel -> label, Axes -> {True, False}, Ticks -> None];
plotrand2[t_, label_] := Show[walls, 
   Plot[{Re[Randpsi2[x, t]], Im[Randpsi2[x, t]]}, {x, 0, 1}], 
   PlotLabel -> label, Axes -> {True, False}, Ticks -> None];
(***Put all the plots together***)
MakeFrame[t_] := GraphicsGrid[
   {{classical[3 t/(4 Pi), "A"], plotpsi[1, t, "B"]},
    {plotpsi[2, t, "C"], plotpsi[3, t, "D"]},
    {plotrand[t, "E"], plotrand2[t, "F"]}},
   Frame -> All, ImageSize -> 300];
output = Table[MakeFrame[t], {t, 0, 4 Pi*138/139, 4 Pi/139}];
SetDirectory["C:\\Users\\Steve\\Desktop"]
Export["test.gif", output, "DisplayDurations" -> 10]

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