All featured a 220V AC supply, a sensor (either an IR distance sensor or a light barrier) to detect the ball, and an Arduino. Actuators were built from hair dryers and portable fans.

But light is intangible -- it would not be able to trip the more traditional Rube Goldberg mechanisms. Therefore, the team chose mechanisms that required heat -- focus a beam of light tightly ...

Max Planck Institute of Quantum Optics. "A 'pin ball machine' for atoms and photons." ScienceDaily. ScienceDaily, 16 April 2015. <www.sciencedaily.com / releases / 2015 / 04 / 150416093924.htm>.