Two trapped ions can cite one shared motional mode, so a drive ledger must name the same packet source for both ions. The shared-mode reference is exact only for the declared mode and packet index; real traps can mix spectator modes, drift in frequency, and accumulate calibration or addressing error.
The shared motional mode is a cited packet ledger. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
The addressed ion uses a checked drive
The drive starts from packet 2 and ends at packet 2.
2→2
Two ion labels cite one shared motional packet without changing it
Ion A cites the same shared packet ledger, ending at packet 2.