# -*- coding: utf-8 -*- """ Experimentul 1 — Delayed Choice Quantum Eraser (Kim, Yu, Kulik, Shih, Scully, PRL 84, 2000) Baza analizei din superluminal.pdf (Lee Wen Wu, 2021), sectiunile 2-3. Simulare cuantica locala (Monte Carlo pe amplitudini): - fotonul semnal cade pe ecranul D0 la pozitia x0, esantionata din |Psi_s(x)|^2; - starea fotonului idler colapseaza partial in alfa|A> + beta|B>, cu alfa = Psi_A(x0), beta = Psi_B(x0) (Eq. 11 din lucrare); - idlerul ajunge la D1/D2 (eraser, prin beam-splitter) sau D3/D4 (which-slit): P(D1) = |alfa+beta|^2/4 P(D2) = |alfa-beta|^2/4 P(D3) = |alfa|^2/2 P(D4) = |beta|^2/2 (Eq. 22, 23, 14, 16) - sortarea pozitiilor x0 dupa detectorul idlerului reconstruieste R01..R04. Concluzia fizica reprodusa: pe D0 TOTAL nu apar franje niciodata; franjele apar numai la sortarea in coincidenta -> nu exista semnalizare (retro)cauzala. """ import sys import numpy as np import tkinter as tk from tkinter import ttk import matplotlib matplotlib.use("TkAgg") from matplotlib.figure import Figure from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg from phys_comun import amplitudini_fante, esantioneaza, contrast_franje, perioada_franje XMAX = 12.0 NX = 2001 NBIN = 121 class AppDCQE: def __init__(self, root): self.root = root root.title("Exp. 1 — Delayed Choice Quantum Eraser (Kim et al. 2000)") self.rng = np.random.default_rng() self.x = np.linspace(-XMAX, XMAX, NX) self.bins = np.linspace(-XMAX, XMAX, NBIN + 1) self.centre = 0.5 * (self.bins[:-1] + self.bins[1:]) self.ruleaza = False # ---- panou de control ---- ctl = ttk.Frame(root, padding=8) ctl.pack(side=tk.LEFT, fill=tk.Y) ttk.Label(ctl, text="Delayed Choice\nQuantum Eraser", font=("Segoe UI", 12, "bold")).pack(pady=(0, 8)) self.btn = ttk.Button(ctl, text="Start", command=self.comuta) self.btn.pack(fill=tk.X, pady=2) ttk.Button(ctl, text="Reset", command=self.reset).pack(fill=tk.X, pady=2) ttk.Label(ctl, text="Fotoni / pas:").pack(anchor="w", pady=(10, 0)) self.v_batch = tk.IntVar(value=400) ttk.Scale(ctl, from_=50, to=3000, variable=self.v_batch).pack(fill=tk.X) ttk.Label(ctl, text="Separare fante d [mm]:").pack(anchor="w", pady=(10, 0)) self.v_d = tk.DoubleVar(value=0.35) ttk.Scale(ctl, from_=0.15, to=0.8, variable=self.v_d, command=lambda e: self.reset()).pack(fill=tk.X) ttk.Label(ctl, text="Latime fanta a [mm]:").pack(anchor="w", pady=(10, 0)) self.v_a = tk.DoubleVar(value=0.08) ttk.Scale(ctl, from_=0.03, to=0.2, variable=self.v_a, command=lambda e: self.reset()).pack(fill=tk.X) self.lbl = ttk.Label(ctl, text="", justify="left", font=("Consolas", 9)) self.lbl.pack(anchor="w", pady=12) ttk.Label(ctl, wraplength=200, justify="left", foreground="#555", text=( "R01/R02: idler la D1/D2 (eraser) -> franje complementare.\n" "R03/R04: idler la D3/D4 (which-slit) -> fara franje.\n" "D0 total = R01+R02+R03+R04 -> fara franje.\n\n" "Franjele exista doar in datele SORTATE in coincidenta, " "deci nu se poate transmite niciun semnal doar prin D0.")).pack(anchor="w") # ---- figura ---- self.fig = Figure(figsize=(9, 7), dpi=100) gs = self.fig.add_gridspec(3, 2, hspace=0.5, wspace=0.3) self.ax0 = self.fig.add_subplot(gs[0, :]) self.ax = [self.fig.add_subplot(gs[1, 0]), self.fig.add_subplot(gs[1, 1]), self.fig.add_subplot(gs[2, 0]), self.fig.add_subplot(gs[2, 1])] self.canvas = FigureCanvasTkAgg(self.fig, master=root) self.canvas.get_tk_widget().pack(side=tk.RIGHT, fill=tk.BOTH, expand=True) self.reset() if "--test" in sys.argv: self.comuta() root.after(2500, root.destroy) # ------------------------------------------------------------------ def reset(self): self.psiA, self.psiB = amplitudini_fante(self.x, self.v_d.get(), self.v_a.get()) self.p0 = (np.abs(self.psiA) ** 2 + np.abs(self.psiB) ** 2) / 2 self.counts = {k: np.zeros(NBIN) for k in ("D0", "D1", "D2", "D3", "D4")} self.total = 0 self.deseneaza() def comuta(self): self.ruleaza = not self.ruleaza self.btn.config(text="Pauza" if self.ruleaza else "Start") if self.ruleaza: self.pas() def pas(self): if not self.ruleaza: return n = int(self.v_batch.get()) x0, idx = esantioneaza(self.x, self.p0, n, self.rng) al, be = self.psiA[idx], self.psiB[idx] s = np.abs(al) ** 2 + np.abs(be) ** 2 # probabilitatile conditionate pentru detectorul idlerului p1 = np.abs(al + be) ** 2 / (4 * s) p2 = np.abs(al - be) ** 2 / (4 * s) p3 = np.abs(al) ** 2 / (2 * s) cum = np.cumsum(np.stack([p1, p2, p3], axis=1), axis=1) u = self.rng.random(n)[:, None] det = (u > cum).sum(axis=1) # 0->D1, 1->D2, 2->D3, 3->D4 self.counts["D0"] += np.histogram(x0, self.bins)[0] for j, nume in enumerate(("D1", "D2", "D3", "D4")): self.counts[nume] += np.histogram(x0[det == j], self.bins)[0] self.total += n self.deseneaza() self.root.after(30, self.pas) # ------------------------------------------------------------------ def deseneaza(self): per = perioada_franje(self.v_d.get()) self.ax0.clear() self.ax0.fill_between(self.centre, self.counts["D0"], color="#444", step="mid") self.ax0.set_title("D0 — toti fotonii semnal (ceea ce vede 'Bob' fara coincidente)") self.ax0.set_xlim(-XMAX, XMAX) culori = ("#1f77b4", "#d62728", "#2ca02c", "#9467bd") titluri = ("R01 (idler la D1 — eraser)", "R02 (idler la D2 — eraser)", "R03 (idler la D3 — which-slit)", "R04 (idler la D4 — which-slit)") for axx, nume, cul, tit in zip(self.ax, ("D1", "D2", "D3", "D4"), culori, titluri): axx.clear() axx.fill_between(self.centre, self.counts[nume], color=cul, step="mid") axx.set_title(tit, fontsize=9) axx.set_xlim(-XMAX, XMAX) v01 = contrast_franje(self.counts["D1"], per, self.centre) v0 = contrast_franje(self.counts["D0"], per, self.centre) self.lbl.config(text=(f"fotoni: {self.total}\n" f"contrast R01: {v01:.3f}\n" f"contrast D0: {v0:.3f}")) self.canvas.draw_idle() if __name__ == "__main__": root = tk.Tk() AppDCQE(root) root.mainloop()