The Entropic regularization of the classical quadratic optimal transport control problem (aka Schr¨odinger problem) can be extended first to solve numerically drift controlled diffusion processes Benamou et al. (2018). Then in a second part he showed how time discretisation of the relative entropy can be used to characterize the (linear) time scaling under which the relative entropy between diffusion processes becomes a divergence between the diffusion coefficients of its arguments instead of blowing up when they are singular. This object is also known as “Specific Relative Entropy”. Then classical Entropic optimal numerical methods, like Sinkhorn, are generalised to diffusion controlled diffusion processes.