Retrieving information from a qubit entering a black hole

As noted in previous posts, perhaps one of the more interesting concepts in quantum physics is the notion of information conservation in/out of a black hole. Stephen Hawking first posited that information is conserved when a particle enters a black hole, via “Hawking radiation”. This involves a particle pair (i.e. quark/antiquark)- one exits the black hole and one enters it, leading to an overall decrease in the black hole mass/black hole evaporation. This seems reasonable, but one problem remains- the information of the particle entering the black hole is somehow lost, as there is no way to observe its change.

A description of Hawking radiation. Source: Nature

A new idea exists for the limit of one quantum particle- a qubit entering a black hole. The idea is that if one is able to observe the spin/angular momentum of the black hole (good luck with that massive object) and release a qubit into the black hole, the information of the qubit becomes entangled with the black hole’s spin. The key is that the observer must already have access to a particle that is ejected from Hawking radiation, such that this particle’s pair becomes entangled with the qubit lost to the black hole. Kinda confusing, but essentially this idea treats the black hole as the observable object when having an entangled particle enter the black hole.

Obviously, this method is severely limited when considering multiple qubits, or potentially even the many states inside the black hole. What if there’s a wormhole? Or (multiverses?) Speaking of multiverses- for those who oppose this idea, Nobel Laureate (and MIT professor) Frank Wilczek notes that overall energy across universes is conserved (via the Hamiltonian), but perhaps energy leaks between universes, a theory he hopes to test soon. So… leaking information, right? Angular momentum of black holes aren’t conserved? Seems to be the logical conclusion for me 🙂

Long story short, more ambiguity, but it looks like the multiverse theory doesn’t seem as far-fetched as it did before!

Information from a black hole

Wilczek leaking energy


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