von Neumann measurement interaction
= von Neumann measurement interaction
{c}
{title2=$U=\exp(-igA\otimes p/\hbar)$}
A coupling between system <observable> $A$ and meter <momentum> $p$ that translates a pointer coordinate by $ga$ for an $A$ eigenvalue $a$. For a <weak measurement>, these translations are small compared with the initial pointer width. Larger separated pointer distributions instead support a sharp readout of the coupled observable.