Measurement of quantum states with incoherent light

A novel and high resolution method for measuring quantum states with incoherent light in the time-domain is presented. Taking Autler-Townes effect as an example, the physical process and the evolution rule during measurement are discussed by an explicit analytical formulation in detail; and the influence of measuring process on the quantum state is disclosed. With this method, very small splitting of the energy-level and large energy-level space can be measured readily at the same time, while the transverse relaxation rate of the system can be obtained directly by checking the decay time of the signal. Compared with the characteristics of the measuring methods between the time-domain and frequency-domain, we found that the measuring quantum states with incoherent light in the time-domain is robust and valid for disclosing information of the quantum state completely.