Probabilistic approximation of the evolution operator $e^{itH}$, where $H=\dfrac{(-1)^md^{2m}}{(2m)!dx^{2m}}$

Two approaches are suggested for constructing a probabilistic approximation of the evolution operator $e^{itH}$, where $H=\dfrac{(-1)^md^{2m}}{(2m)!dx^{2m}}$, in the strong operator topology. In the first approach, the approximating operators have the form of expectations of functionals of a certain Poisson point field, while, in the second approach, the approximating operators have the form of expectations of functionals of sums of independent identically distributed random variables with finite moments of order $2m+2$.