  Photonics offers unique capabilities for quantum information processing (QIP)
such as room-temperature operation, the scalability of nanophotonics, and
access to ultrabroad bandwidths and consequently ultrafast operation.
Ultrashort-pulse sources of quantum states in nanophotonics are an important
building block for achieving scalable ultrafast QIP, however, their
demonstrations so far have been sparse. Here, we demonstrate a femtosecond
biphoton source in dispersion-engineered periodically poled lithium niobate
nanophotonics. We measure 17 THz of bandwidth for the source centered at 2.09
\textmu m, corresponding to a few optical cycles, with a brightness of 8.8
GHz/mW. Our results open new paths towards realization of ultrafast
nanophotonic QIP.
