  Generations of technologies with fundamentally new information processing
capabilities will emerge if microscopic physical systems can be controlled to
encode, transmit, and process quantum information, at scale and with high
fidelity. In the decade after its 2008 inception, the technology of integrated
quantum photonics enabled the generation, processing, and detection of quantum
states of light, at a steadily increasing scale and level of complexity. Using
both established and advanced fabrication techniques, the field progressed from
the demonstrations of fixed circuits comprising few components and operating on
two photons, to programmable circuitry approaching 1000 components with
integrated generation of multi-photon states. A continuation in this trend over
the next decade would usher in a versatile platform for future quantum
technologies. This Review summarises the advances in integrated photonic
quantum technologies (materials, devices, and functionality), and its
demonstrated on-chip applications including secure quantum communications,
simulations of quantum physical and chemical systems, Boson sampling, and
linear-optic quantum information processing.
