  Future quantum computers require a scalable architecture on a scalable
technology---one that supports millions of high-performance components.
Measurement-based protocols, based on graph states, represent the state of the
art in architectures for optical quantum computing. Silicon photonics offers
enormous scale and proven quantum optical functionality. Here we report the
first demonstration of photonic graph states on a mass-manufactured chip using
four on-chip generated photons. We generate both star- and line-type graph
states, implementing a basic measurement-based protocol, and measure heralded
interference of the chip's four photons. We develop a model of the device and
bound the dominant sources of error using Bayesian inference. The two-photon
barrier, which has constrained chip-scale quantum optics, is now broken; future
increases in on-chip photon number now depend solely on reducing loss, and
increasing rates. This experiment, combining silicon technology with a
graph-based architecture, illuminates one path to a large-scale quantum future.
