CherryWull

The answer is a direct conclusion of polar decomposition. [https://en.wikipedia.org/wiki/Polar_decomposition](url) In short, any square complex matrix $M$ has a decomposition of the form $M=U P$, where $U$ is unitary and...

> Doesn't the squareness depend on your basis? Unless I'm missing something you can always make the measurement operator have a square matrix representation by padding it with `0`s where...