The Wigner distribution function is one of the pillars of the phase space formulation of quantum mechanics. Its original formulation may be cast in terms of the unitary representations of the Weyl–Heisenberg group. Following the construction proposed by Wolf and coworkers in constructing the Wigner functions for general Lie groups using the irreducible unitary representations of the groups, we develop here the Wigner functions and Weyl operators on the Euclidean motion group of rank three. We give complete derivations and proofs of their important properties.
The Heisenberg-Weyl group
HW(d) related to a
d-dimensional Hilbert space
H(d), is enlarged into the Heisenberg-Weyl-parity group
HWP(d) that incorporates parity transformations. It consists of
2d3 elements, of which
d3 elements belong to the
HW(d) subgroup, and extra
d3 elements which are related through a Fourier transform with the former ones. It is shown that
HWP(d) is a generalised version of the dihedral group. The properties of operators that combine displacements and parity, are discussed.
HWP(d) is shown to be a solvable group, and commutators of its elements perform displacement and parity transformations of quantum states, along loops in the discrete phase space.
2d2 coherent states related to the
HWP(d) group are introduced, which consist of
d2 coherent states related to the
HW(d) subgroup, and extra
d2 coherent states which are related through a Fourier transform with the former ones. In noisy cases, expansion of an arbitrary state in terms of the
2d2 coherent states with Bargmann coefficients, is advantageous in comparison to expansion in terms of the
d2 coherent states related to
HW(d). One of the consequences of the
HWP(d) group, is a natural unification of the Wigner and Weyl functions. The properties of the unified Wigner-Weyl function are discussed.