sharp-sightedness vs on the qui vive

sharp-sightedness and on the qui vive both are nouns.

Word	Noun	Adjective	Verb	Adverb
sharp-sightedness	Yes	No	No	No
on the qui vive	Yes	No	No	No

As nouns, sharp-sightedness and on the qui vive are synonyms defined as:

Other synonyms of sharp-sightedness include alertness.

sharp-sightedness (noun)	on the qui vive (noun)
lively attentiveness	lively attentiveness
sharpness of vision; the visual ability to resolve fine detail (usually measured by a Snellen chart)