How do qubits flow through spacetime?
Abstract: I will discuss new developments in our understanding of the holographic principle, and the way in which it changes our understanding of spacetime. In this new picture, information (qubits) of spcetime are stored not on 3-dimensional time slices, but on 2-dimensional surfaces. A 3-dimensional slice is thus a quantum process, and 4-dimensional time evolution represents an equivalence of such processes. However, in order to recover general relativity, the theory that lives on 3-dimensional slices cannot be a normal unitary theory! Instead, it exhibits a phase transition, where at a certain point in the spectrum, the energy eigenvalues become imaginary rather than real. I will argue that we must accept these imaginary energies, if we want relativistic spacetime physics to emerge from quantum information theory.