I read a book back in the mid to late 1990s which I have been unable to recall the title or locate through Google.
My recollection of the plot involves an artificial intelligence that has hired a group of people to travel to the United States and find out why the country has gone dark (no people or communications coming out of it). The hired people travel there and they don't find any sign of adults, alive or dead, however, the remains of infants and pets were found.
In this world quantum computers have supplanted traditional binary computers, being used in all electronic devices. These quantum computers had a side effect of moving the user to another quantum reality. While most reality moves would be very small and the changes not noticeable, occasionally people would be moved to a reality where their fortunes would be greatly changed (for good or ill).
The United States of the reality where the story takes place had created something like a Department of Happiness and the AI in charge of it determined that the best way to make all of the people happy was to keep everyone jumping between realities, hoping for one where they are much better off. As pets and infants didn't use computers they got left behind and starved.
There was a section towards the end where a couple of the main characters wind up living digitized inside of a computer for a few years for some reason. I don't recall how this tied into the main story.