An interesting two-page note showing that the deep circular quantum
square well (solvable in terms of Bessel functions) is also
tractable, algebraically, by means of elementary creation and
annihilation operators in two variables.


MR2719088 Sun, Guo-Hua; Dong, Shi-Hai New type operators for
circular well potential in two dimensions. Phys. Lett. A 374 (2010),
no. 40, 4112--4114. 81Q05