[1] After holding postdoctoral research positions in Auckland and Stuttgart, Walls became a senior lecturer in physics at the University of Waikato in 1972, where he became professor in 1980.

Together with his colleague Crispin Gardiner, during the next 25 years he established a major research centre for theoretical quantum optics in New Zealand and built active and productive collaborations with groups throughout the world.

A seminal paper[2] by Walls with his first graduate student Howard Carmichael, showed how to create antibunched light, in which photons arrive at regular intervals, rather than randomly.

The Dan Walls Medal is awarded to "the physicist working in New Zealand who is deemed to have made the greatest impact nationally and/or internationally in their field through predominantly New Zealand-based research".

[8] Winners have included Paul Callaghan, David Parry, Jeff Tallon, Matt Visser, Howard Carmichael, Peter Schwerdtfeger, and Jenni Adams.