  Cellular automata are a class of computational models based on simple rules
and algorithms that can simulate a wide range of complex phenomena. However,
when using conventional computers, these 'simple' rules are only encapsulated
at the level of software. This can be taken one step further by simplifying the
underlying physical hardware. Here, we propose and implement a simple photonic
hardware platform for simulating complex phenomena based on cellular automata.
Using this special-purpose computer, we experimentally demonstrate complex
phenomena including fractals, chaos, and solitons, which are typically
associated with much more complex physical systems. The flexibility and
programmability of our photonic computer presents new opportunities to simulate
and harness complexity for efficient, robust, and decentralized information
processing schemes using light.
