=

The passage around this formula

Applied to position, the same object, $x_w$ = $\langle$ f|$\hat x$|$\psi$$\rangle$/$\langle$ f|$\psi$$\rangle$ , is this atlas’s fifth chart, and it is admitted with a label the other four do not carry. $x_w$ answers a genuinely different question from every chart above: not “what does this state’s position operator return,” but “what does a weakly coupled pointer’s mean reading become, once conditioned on an event that filters the ensemble after the fact.” Because the conditioning can make $\langle$ f|$\psi$$\rangle$ arbitrarily small, $x_w$ can be pushed arbitrarily far from anything the Møller disk or the Pryce trade-off constrains; it is not bounded by $\rho_M$ , and it does not need to be, because it was never…

Read this part in the article →