Persistent energy-time entanglement covering multiple resonances of an   on-chip biphoton frequency comb
  We investigate the time-frequency signatures of an on-chip biphoton frequency comb (BFC) generated from a silicon nitride microring resonator. Using a Franson interferometer, we examine the multifrequency nature of the photon pair source in a time entanglement measurement scheme; having multiple frequency modes from the BFC results in a modulation of the interference pattern. This measurement together with a Schmidt mode decomposition shows that the generated continuous variable energy-time entangled state spans multiple pair-wise modes. Additionally, we demonstrate nonlocal dispersion cancellation, a foundational concept in time-energy entanglement, suggesting the potential of the chip-scale BFC for large-alphabet quantum key distribution. 
Jose A. Jaramillo-Villegas, Poolad Imany, Ogaga D. Odele, Daniel E.   Leaird, Zhe-Yu Ou, Minghao Qi and Andrew M. Weiner
quant-ph physics.optics