I have often used the almost equivalent term “Time Scanning”, but I see that more and more people are using “Quantum Archaeology”. A short definition:
Quantum Archaeology is a set of hypothetical far future technologies that, presumably through the application of yet undiscovered quantum effects, will permit reconstructing past events up to any desired resolution in space and time. In particular, Quantum Archaeology will permit reconstructing the life, thoughts, memories and feelings of any person in the past, up to any desired level of detail, and thus resurrecting the original person via “copying to the future.”
A practical analogy for QA:
A few weeks ago I wiped clean an old website of mine (I deleted everything, html and php pages, and the entire mysql database). Only yesterday I realized that I had deleted the only existing copy of an article that I wrote in 2005 jointly with one of my favorite SF writers. The article was dead, and with no backup copies anywhere. I was really mad.
Then today I thought that perhaps the (Holy?) Ghost in the Machine (Internet) had made a backup copy of the article. I found a copy on the Internet Archive, incomplete but good enough as a starting point for reconstruction (resurrection).
So I have resurrected the article. It has taken some work, but here it is, and I think some people here may like it:
Shadows and the concept of self
By Giulio Prisco and Richard L. Miller
We die, and if we have no backup copies (e.g. a chemically preserved brain, a frozen body, a mindfile) our death is irreversible.
Or is it?
Perhaps the machinery of the universe creates backup copies, and if our descendants (or aliens, or AIs) find our backup copies, they will be able to resurrect us.
How? Some preliminary thoughts:
1) Other times are special cases of other universes (other branches of the MWI multiverse). If quantum entanglement extends across time, then it should be possible to find present systems correlated to past systems.
2) In the MWI there is no collapse of the state vector that irreversibly discards information. This should imply that information is preserved in the multiverse.
3) Reversible computing is the most energy-efficient form of computing, because only destroying information requires energy. If reversible computing is the most energy-efficient form of computing, it makes sense to think that the universe does reversible computing, and all information lost is available in “hidden output registers” that we could eventually find and read.