Decoding a black hole: quantum information theory meets quantum gravity

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Will the information thrown into a black hole be destroyed, or might it be recovered from the Hawking radiation that is emitted as the black hole evaporates? The black hole information puzzle, originally posed by Hawking in 1970s, has remained as one of the most fascinating yet challenging open questions in theoretical physics, highlighting the challenge in reconciling general relativity with quantum mechanics. Evidence from string theory, namely the AdS/CFT correspondence, suggests that the information, rather than being destroyed, can be encoded in the black hole's internal degrees of freedom and eventually transferred to the outgoing radiation. However, the issue remains controversial, and the mechanism by which the information escapes from a black hole remains elusive. Quantum information theory addresses quantitative questions about the acquisition, transmission, and processing of information in quantum systems. Though quantum information theory by itself cannot resolve the black hole information puzzle, it can provide intuition and analytical/numerical tools that help to sharpen our understanding of the question. The last five years witnessed how applications of theoretical ideas from quantum information science to quantum gravity questions lead to breakthrough ideas. A hallmark of recent fruitful synergy is my own work on a toy model of the AdS/CFT correspondence based on a novel construction of quantum error-correcting codes. The model provided sharp insights on a rather surprising relation between gravity and quantum entanglement through the lens of quantum coding theory. In this research program, I will address various puzzles concerning black holes and quantum gravity, including the aforementioned information problem, by utilizing techniques from modern quantum information theory. This direction of research, addressing fundamental questions at the forefront of quantum gravity and string theory, provides a link to active areas in quantum information theory, such as quantum channels/communication, quantum error-correcting codes, tensor network techniques and quantum algorithms. Furthermore, it opens new research avenues at the interface between quantum gravity, quantum information theory and condensed matter theory. Studies of exotic properties of black holes through the lens of quantum information theory will also provide useful new tools/concepts for quantum information theory itself. Experimental simulations of the chaotic behaviour of black holes may provide an ideal platform for demonstrating the advantage of quantum systems over classical systems. These questions will also bring insights from theoretical physics to further advance our understanding of quantum information theory itself.