In this paper we discuss a family of models of particle and energy diffusion
on a one-dimensional lattice, related to those studied previously in
[Sasamoto-Wadati], [Barraquand-Corwin] and [Povolotsky] in the context of KPZ
universality class. We show that they may be mapped onto an integrable
$\mathfrak{sl}(2)$ Heisenberg spin chain whose Hamiltonian density in the bulk
has been already studied in the AdS/CFT and the integrable system literature.
Using the quantum inverse scattering method, we study various new aspects, in
particular we identify boundary terms, modeling reservoirs in non-equilibrium
statistical mechanics models, for which the spin chain (and thus also the
stochastic process) continues to be integrable. We also show how the
construction of a "dual model" of probability theory is possible and useful.
The fluctuating hydrodynamics of our stochastic model corresponds to the
semiclassical evolution of a string that derives from correlation functions of
local gauge invariant operators of $\mathcal{N}=4$ super Yang-Mills theory
(SYM), in imaginary-time. As any stochastic system, it has a supersymmetric
completion that encodes for the thermal equilibrium theorems: we show that in
this case it is equivalent to the $\mathfrak{sl}(2|1)$ superstring that has
been derived directly from $\mathcal{N}=4$ SYM.