"Problem 15.6.1" ahat(f) = sqrt(1/2) (f xi + d(f,xi)) ahatdag(f) = sqrt(1/2) (f xi - d(f,xi)) ket0 = pi^(-1/4) exp(-xi^2 / 2) -- see equation (15.33) ket(n) = test(n < 0, 0, n == 0, ket0, sqrt(1/n) ahatdag(ket(n - 1))) psi(n) = sqrt(nbar^n exp(-nbar) / n!) exp(-i (n + 1/2) omega t) ket(n) -- use N instead of infinity N = 10 Psi = sum(n,0,N,psi(n)) A = ahat(Psi) B = sqrt(nbar) exp(-i omega t) (Psi - psi(N)) -- correction for finite N check(A == B) "ok" Run