Spin lattices, state transfer and bivariate Krawtchouk polynomials
  The quantum state transfer properties of a class of two-dimensional spin lattices on a triangular domain are investigated. Systems for which the 1-excitation dynamics is exactly solvable are identified. The exact solutions are expressed in terms of the bivariate Krawtchouk polynomials that arise as matrix elements of the unitary representations of the rotation group on the states of the three-dimensional harmonic oscillator. 
Vincent X. Genest, Hiroshi Miki, Luc Vinet and Alexei Zhedanov
math-ph math.MP quant-ph