> Fine, I'll add 11 bits to my key length, come back when you've developed a computer with 2000x the phase precision.

the really weird thing it's what this isn't true. we already have quantum error correction schemes that can take a quantum computer with O(1) error and get O(exp(-k)) error with polylog(k) inaccurate qbits (and we have empirical evidence that these schemes work to correct the error of single digit numbers of qbits already). adding 11 bits to the key adds ~12 logical qbits or ~a hundred physical qbits to the side of the QC