My layman's understanding of QFT is that once a system is observed, any future observation will always yield the same result. Would this hold true if the original-and-only observer, without any physical recording other than human memory, and not communicated to any other person, died before any subsequent observation?
If the plot of the film was, "the spy sent the vital, world-saving data back to headquarters, encoded with a quantum key, only to be intercepted and viewed by the antagonist of the story; but the dashing hero catches and kills him before he could reveal what he learned, and the data arrives still encrypted back at HQ", what would the physicists be muttering to each other as they left the theater?
Or put another way, If I flip a coin into a box, observe it, then bury the box until after my death, does the coin exist in a "superimposed" state of heads/tails/on the edge until observed again, or will any future observation always be what I saw; or would it be that "superimposed" state but always resolve to the same answer? (apologies if I'm using terms incorrectly).
My intuition says information is information, so even if lost to our access within decaying brain cells, HQ would know the data had been viewed, no matter the state of decomposition of the "person who did the measuring" but I've run into a road block in phrasing the questions to dive deeper down the rabbit hole.
What resources would one recommend --to a well-read layperson who has little trouble following most Royal Institute lectures, to give you an idea of my reading level --to further pursue this odd question?