Playing pool with |ψi: From bouncing billiards to quantum search

Abstract

In “Playing Pool with π” [1], Galperin invented an extraordinary method to learn the digits of π by counting the collisions of billiard balls. Here I demonstrate an exact isomorphism between Galperin’s bouncing billiards and Grover’s algorithm for quantum search. This provides an illuminating way to visualize Grover’s algorithm.