Complexity and control in quantum photonics : doctoral thesis accepted by the University of Bristol UK This work explores the scope and flexibility afforded by integrated quantum photonics both in terms of practical problem solving and for the pursuit of fundamental science. The author demonstrates and fully characterizes a two qubit quantum photonic chip capable of arbitrary two qubit state preparation. Making use of the unprecedented degree of reconfigurability afforded by this device a novel variation on Wheelers delayed choice experiment is implemented and a new technique to obtain nonlocal statistics without a shared reference frame is tested. Also presented is a new algorithm for quantum chemistry simulating the helium hydride ion. Finally multiphoton quantum interference in a large Hilbert space is demonstrated and its implications for computational complexity are examined.