**Quantum quincunx in cavity quantum elecrodynamics**

The random walk is interesting both as a concept underpinning diffusive processes as well as a basis for search algorithms in computer science, and Galton's quincunx demonstrates the dispersion characteristic of random walks. Recent work has established that quantisation of the random walk, known as the quantum walk, leads to a quadratic enhancement of spreading. We propose a quantum walk on a circle as a coherent field state in a cavity that undergoes kicks from a two-level atom. The phase of the field diffracts quadratically faster than the allowed diffusion rate for classical random walks. This proposed experiment would yield the first realization of a quantum quincunx and may be useful both for enhancing phase diffusion and as a quantum algorithm.