wlist = linspace(-w0-0.2,w0+0.2,250)
#eseries method
sp1 = spectrum(H,wlist,c_ops,sm.dag(),sm,solver='es', use_pinv=False)
#pi method without pinv
sp2 = spectrum(H,wlist,c_ops,sm.dag(),sm,solver='pi', use_pinv=False)
#pi method with pinv
sp3 = spectrum(H,wlist,c_ops,sm.dag(),sm,solver='pi', use_pinv=True)
#sp using the older spectrum_ss function
sp4 = spectrum(H,wlist,c_ops,sm.dag(),sm)
#plot the results
plot(wlist,sp1,lw=3,label='eseries method')
plot(wlist,sp2,lw=3,linestyle='--',label='use_pinv=False')
plot(wlist,sp3,'o',label='use_pinv=True')
plot(wlist,sp4,lw=3,linestyle='--',label='old_function')
xlabel('Frequency')
ylabel('Emission')
legend(loc='upper center')
savefig('2LS_emission_problem.png')
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------