“…From a purely theoretical point of view, there is no need to restrict our attention to geometrical structures on quantum states associated with covariant tensor fields as in the case of metric tensors discussed above. Indeed, in [ 19 , 20 , 21 , 22 , 23 , 24 , 25 ], the associative product of the algebra of linear operators on the finite-dimensional Hilbert space associated with a quantum system has been suitably exploited to define two contravariant tensor fields on the space of self-adjoint operators on , and these tensor fields have been used to give a geometrical description of the Gorini–Kossakowski–Lindblad–Sudarshan (GKLS) equation describing the dynamical evolution of open quantum systems (see [ 19 , 21 , 22 , 24 , 26 , 27 , 28 ]). These two tensor fields, named and , are associated with the antisymmetric part (the Lie product) and the symmetric part (the Jordan product) of the associative product in , respectively.…”