Time-Resolved Hanbury Brown–Twiss Interferometry of On-Chip Biphoton Frequency Combs Using Vernier Phase Modulation

Biphoton frequency combs (BFCs) are promising quantum sources for large-scale and high-dimensional information networking systems. In this context, the spectral purity of individual bins will be critical realizing protocols like teleportation entanglement swapping. Measurement temporal autocorrelation function unheralded signal or idler photons comprising BFC is a key tool characterizing their in turn verifying utility biphoton state protocols. Yet experimentally obtainable precision measuring correlation functions often severely limited by detector jitter. The fine features function---not only practical value information, but also fundamental interest study optics---are lost as result. We propose scheme to circumvent challenge through electro-optic phase modulation, demonstrating time-resolved Hanbury Brown--Twiss characterization BFCs generated from an integrated 40.5-GHz ${\mathrm{Si}}_{3}{\mathrm{N}}_{4}$ microring, up $3\ifmmode\times\else\texttimes\fi{}3$-dimensional two-qutrit Hilbert space. Through slight detuning drive comb's free range, our approach leverages Vernier principles magnify features, which would otherwise averaged out demonstrate under both continuous-wave pulsed-pumping regimes, finding excellent agreement with theory. Our method reveals not collective statistics contributing shapes---features standard fully measurements.