The authors report on an approach to detect excitonic qubits in semiconductor quantum dots by observing spontaneous emissions from the relevant qubit level. The ground state of excitons is resonantly excited by picosecond optical pulses. Emissions from the same state are temporally resolved with picosecond time resolution. To capture weak emissions, the authors greatly suppress the elastic scattering of excitation beams, by applying obliquely incident geometry to the microphotoluminescence setup. Rabi oscillations of the ground-state excitons appear to be involved in the dependence of emission intensity on excitation amplitude.