Bad Qubits — Learn Quantum by Doing

Multiple choice

Under pure dephasing the off-diagonal density-matrix element obeys d(rho_01)/dt = -gamma rho_01, so rho_01(t) = rho_01(0) e^(-gamma t). With gamma = 0.8 (per unit time) and rho_01(0) = 0.5, what is rho_01 at t = 1.25?

1.359
0.303
0.368
0.184