Abstract: A system for estimating values of a vector of variables that optimize a function comprising a weighted sum of interactions between the variables; the system comprising a plurality of parallel hardware channels, each arranged to model a contribution of a respective variable to the function, each channel comprising: a signal generator configured to generate a signal modelling a value of the respective variable; a splitter arranged to supply the signal to each of the channels; interaction logic configured to multiply the vector of signals by a vector of weights modelling an interaction between the respective variable and the vector of variables, thereby generating a feedback signal representing the contribution of the respective variable; and a feedback path to return the feedback signal to the signal generator configured to adapt the signal in dependence on the feedback signal, wherein each channel is implemented only using optical components and/or analogue electronic components.