Clear[Axs]
Clear[Ixs]
Clear[AIx]
Clear[Ro1]
Clear[Ro]
Clear[R1]
Clear[R2]
Clear[R3]
Clear[FF]
Clear[y]
Clear[H]
Clear[ge]
Clear[mb]
Clear[Bz]
Clear[Apar]
Clear[Aperp]
Clear[DNV]
Clear[H]
Clear[Detuning]
Clear[t]
(*NV papameters*)


Ro:=(({{1, 0}, {0, 0}}))

sx:=PauliMatrix[1];
sy:=PauliMatrix[2];
sz:=PauliMatrix[3];
ix:=PauliMatrix[1];
iy:=PauliMatrix[2];
iz:=PauliMatrix[3];
plus:=(({{0, 1}, {0, 0}}))
minus:=(({{0, 0}, {1, 0}}))
un:=(({{1, 0}, {0, 1}}))
(*R1:=MatrixExp[-t*I*(ix)].Ro.MatrixExp[t*I*(ix)]*)
R1:=MatrixExp[-0.5*I*(ix)].Ro.MatrixExp[0.5*I*(ix)]
R2:=MatrixExp[-I*t*2*(iz)].R1.MatrixExp[I*t*2*(iz)]
Res1:=R2
Pop=Re[Part[Res1,2,1]];

Plot[Pop, {t,0,5}, PlotPoints->100]