new viewpoint out in quantum.

Quantum just published a viewpoint of mine on great work of Banchi and Crooks on a stochastic parameter-shift rule.

Among other things, the viewpoint also features a very gentle introduction to NISQ computing, variational quantum algorithms and optimization of such algorithms with gradients. I also added an intuitive explainer of the parameter-shift rule based on recent work about the relation between parametrized gates and the Fourier coefficients of expectation values that depend on them.