In ``Playing Pool with $\pi$'' , Galperin invented an extraordinary method to learn the digits of $\pi$ 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.
 G. Galperin, ``Playing pool with $\pi$'', Regular and Chaotic Dynamics, v. 8, no. 4 (2003).
 L. K. Grover, ``A Fast quantum mechanical algorithm for database search,'' Proceedings, 28th Annual ACM Symposium on the Theory of Computing (STOC), 1996, pages 212-219; arXiv:quant-ph/9605043.
 Don Monroe, "Bouncing balls and quantum computing", Communications of the ACM 63 10, 10 (2020).
 X. M. Aretxabaleta, M. Gonchenko, N. L. Harshman, S. G. Jackson, M. Olshanii, and G. E. Astrakharchik, "The dynamics of digits: Calculating pi with Galperin's billiards", arXiv:1712.06698.
 Jiang Liu, "A Classical $\pi$ Machine and Grover's Algorithm", arXiv:2105.10257.
The above citations are from Crossref's cited-by service (last updated successfully 2021-06-16 01:45:12) and SAO/NASA ADS (last updated successfully 2021-06-16 01:45:14). The list may be incomplete as not all publishers provide suitable and complete citation data.
This Paper is published in Quantum under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. Copyright remains with the original copyright holders such as the authors or their institutions.