  In magnetism, skyrmions correspond to classical three-dimensional spin
textures characterized by a topological invariant that keeps track of the
winding of the magnetization in real space, a property that cannot be easily
generalized to the quantum case since the orientation of a quantum spin is in
general ill-defined. Moreover, as we show, the quantum skyrmion state cannot be
directly observed in modern experiments that probe the local magnetization of
the system. However, we show that this novel quantum state can still be
identified and fully characterized by a special local three-spin correlation
function defined on neighbouring lattice sites -- the scalar chirality -- which
reduces to the classical topological invariant for large systems, and which is
shown to be nearly constant in the quantum skyrmion phase.
