  The versatility of silicon photonic integrated circuits has led to a
widespread usage of this platform for quantum information based applications,
including Quantum Key Distribution (QKD). However, the integration of simple
high repetition rate photon sources is yet to be achieved. The use of
weak-coherent pulses (WCPs) could represent a viable solution. For example,
Measurement Device Independent QKD (MDI-QKD) envisions the use of WCPs to
distill a secret key immune to detector side channel attacks at large
distances. Thus, the integration of III-V lasers on silicon waveguides is an
interesting prospect for quantum photonics. Here, we report the experimental
observation of Hong-Ou-Mandel interference with 46\pm 2% visibility between
WCPs generated by two independent III-V on silicon waveguide integrated lasers.
This quantum interference effect is at the heart of many applications,
including MDI-QKD. Our work represents a substantial first step towards an
implementation of MDI-QKD fully integrated in silicon, and could be beneficial
for other applications such as standard QKD and novel quantum communication
protocols.
