Conditional spectroscopy via nonstationary optical homodyne quantum state tomography

Abstract

Continuous variable quantum state tomography is one of the most powerful techniques to study the properties of light fields in quantum optics. However, the need for a fixed phase reference has so far prevented widespread usage in other fields such as semiconductor spectroscopy. Here, we introduce non-stationary quantum state tomography, which adapts the technique to the special requirements of ultrafast spectroscopy. In detail, we gain access to the amplitude and phase of light fields with a temporal resolution of about 100 fs without the need for a fixed phase reference. Further, we show how our technique allows us to perform conditional studies of stochastic dynamics that are inaccessible experimentally by conventional means, and demonstrate the capabilities experimentally by monitoring the stochastic dynamics of a thermal light field on the sub-ps scale. Finally, we discuss differences and similarities to more standard Hanbury Brown-Twiss photon correlation experiments, which may be considered as the discrete variable analogues of our technique.

Distinguishing intrinsic photon correlations from external noise with frequency-resolved homodyne detection

“…As an outlook, it will be interesting to extend this conditional spectroscopy setup to several detection channels 43 . Doing so will open up the possibility to perform conditional measurements of cross-correlations between several detection channels 44 .…”

Quantifying quantum coherence in polariton condensates

“…Therefore, in a measurement that takes several 100 milliseconds to accumulate enough quadrature values, we average over all phases between signal and LO and receive a phase-averaged version of the actual Q function. The phase information could be obtained by employing more homodyne channels and reconstructing the relative phase between them [72]. However, the phase-averaged Q function already provides the necessary information since Eq.…”