Another math koan. Left hand side, purely classical probability vector. Right hand side, an inner product of purely quantum quantities: measurement operator μ and density operator ρ
How can this fundamental theorem of quantum information be so simple and yet so subtle?

Just to take my mind of off the stock market crash, here is my entry for the weirdest way to write a second order ordinary differential equation:

I like x for grok:

Hey Grok: the parallel transport map of a given connection, acting on the set of all closed paths on a vector bundle and containing any fixed point, forms a Lie group under composition of the map, called the holonomy group. Draw an illustration using cats.