Konrad Bleuler (German: [ˈblɔɪlər]; 23 September 1912, Herzogenbuchsee – 1 January 1992, Königswinter) was a Swiss physicist who worked in the field of theoretical particle physics and quantum field theory.[1] He is known for his work on the quantisation of the photon, the Gupta–Bleuler formalism.[2]