There is described a system for determining a modal property of a quantum state. The system generally has a quantum light source generating an optical pulse having a given frequency, a pulse time duration and a quantum state with a modal property; a local pulse generator having: a laser source generating a local optical signal having a frequency associated to the given frequency; an optical modulator modulating the local optical signal; and an arbitrary wave generator supplying electrical waveforms to the optical modulator for said modulating, said modulating including forming local optical pulses from the local optical signal, the local optical pulses being distributed within the pulse time duration; and a homodyne detector optically coupled to the quantum light source and to the local pulse generator for performing two-time correlation measurements being indicative of the modal property of the quantum state of the given optical pulse.