Wigner-Dyson density or NNSD (Nearest Neighbour Spacing Distribution) of a Hamiltonian of a quantum system behaves in a certain distribution. This distribution is quite different than Poisson and distinctly differentiates chaotic behaviour in Quantum mechanics. It actually means, the quantum version of the classically chaotic system’s Hamiltonian matrix has this property.

Available on v0.2.11 of Leymosun package.