  A key challenge for quantum science and technology is to realise large-scale,
precisely controllable, practical systems for non-classical secured
communications, metrology and ultimately meaningful quantum simulation and
computation. Optical frequency combs represent a powerful approach towards
this, since they provide a very high number of temporal and frequency modes
which can result in large-scale quantum systems. The generation and control of
quantum optical frequency combs will enable a unique, practical and scalable
framework for quantum signal and information processing. Here, we review recent
progress on the realization of energy-time entangled optical frequency combs
and discuss how photonic integration and the use of fiber-optic
telecommunications components can enable quantum state control with new
functionalities, yielding unprecedented capability.
