What does this equation mean?

​ that redshifts everything else in this ledger. The effect does not respect the static/free-fall distinction drawn above: a free-falling register still occupies a finite physical extent across which the local rate of proper time is not perfectly uniform, so “free fall is locally ordinary” is a first-order statement, valid only to the extent that this second-order time-dilation-gradient effect stays small across the register’s own size and coherence time. A qubit register large enough, or held coherent long enough, for this effect to matter would decohere its own internal superpositions from the metric alone, independent of every resource term counted above — a caveat this paper imports rather than derives, and one more reason the regime in which $N_\perp$[$\Gamma$] 's unitary bookkeeping is even the right description of the hardware is narrower than the flat-space quantum speed limit literature alone would suggest.