1% Pauli operators and Hamiltonian for a two-level atom (Sec. III.C)
2% H = (hbar*omega_0/2) sigma_z
3% sigma_+ raises (|g> -> |e>) and sigma_- lowers (|e> -> |g>).
5clear; % Clear memory
6clc; % Clear the command window/screen
7hbar = 1;
8Omega_0 = 1; % atomic transition frequency
9Sz = [1 0; 0 -1] % sigma_z operator
10Splus = [0 1; 0 0] % raising operator sigma_+
11Sminus = [0 0; 1 0] % lowering operator sigma_-
12H = hbar*Omega_0/2*Sz % Hamiltonian for a two-level atom