In recent years, the main quest of quantum optics has been to show that quantum concepts surpass their classical counterparts. In communication, computation and metrology, this necessitates the implementation of large Hilbert spaces, spanned by network size and photon number. Therefore, the challenge is to implement large quantum networks with many photons.Here, we present new techniques aiming towards this goal. We begin our discussion with a dual-path waveguide source that uses the underlying waveguide architecture to tailor the non-linear state generation and produces post-selection free 2-photon N00N states. Then, we apply this source in the few photon regime. To this aim, we consider the fundamental limits of the time-multiplexed measurement method and calibrate a state-of-the-art implementation of this technique. Consequtively, we apply our source for quantum communication to simulate the effects of atmospheric turbulence on a transmitted signal. Finally, we increase the number of waveguides and implement a non-linear waveguide array. Based on this system, we develop the concept of driven quantum walks that allows us to probe fundamentally different dynamics compared to passive systems. Furthermore, we utilise the intrinsically non-linear waveguide array for the intrinsically linear computational problem of BosonSampling. Finally, we answer the question whether sampling from Gaussian states is hard-to-solve on a classical computer in the affirmative.