Spacetime and future quantum theory

Tadashi Takayanagi

Holographic duality describes gravitational theories in terms of quantum many-body systems. In holography, quantum information theory provides a crucial tool that directly connects microscopic structures of these systems to the geometries of gravitational spacetimes. One manifestation is that the entanglement entropy in quantum many-body systems can be calculated from the area of an extremal surface in the corresponding gravitational spacetime. This implies that a gravitational spacetime can emerge from an enormous number of entangled qubits. In this Essay, I will discuss open problems in this area of research, considering recent developments and outlining future prospects towards a complete understanding of quantum gravity. The first step in this direction is to understand what kind of quantum circuits each holographic spacetime corresponds to, drawing on recent developments in quantum complexity theories and studying concrete examples of holography in string theory. Next, we should extend the concept of holography to general spacetimes, e.g., those spacetimes which appear in realistic cosmologies, by utilizing the connections between quantum information and holography. To address the fundamental question of how time emerges, I will propose the concepts of pseudoentropy and timelike entanglement as a useful tool in our exploration. Part of a series of Essays in Physical Review Letters which concisely present author visions for the future of their field.

Carl Friedrich von Weizsäcker, Thomas Görnitz, Holger Lyre

悠斗 小川

This paper extends the original framework of Future Convergence Theory by incorporating elements from general relativity, quantum mechanics, information theory, and cognitive science into a unified mathematical model. The study introduces a Future Determinacy Function F(T), which evolves under the influence of spacetime geometry, quantum probability distributions, and entropy changes associated with conscious states.We propose the following key extensions:1.Integration with General Relativity: The future determinacy is affected by spacetime curvature, modeled via a term proportional to G_{\mu\nu} U^\mu U^\nu.2.Quantum Mechanical Influence: The future determinacy modifies the Schrödinger equation by introducing a correction term - i \lambda F \Psi, implying that the collapse of quantum states is influenced by the degree of future convergence.3.Information-Theoretic Considerations: The evolution of consciousness is linked to entropy changes, described by \frac{dC}{dT} = -\alpha C + \beta U(T) + \gamma \frac{dS}{dT}, suggesting that conscious perception may depend on the flow of future information.4.Experimental Considerations: We propose that these theoretical predictions could be tested through quantum experiments, EEG-based cognitive studies, and astrophysical observations of local spacetime perturbations.This work aims to redefine the nature of time, probability, and consciousness by suggesting that future information may causally influence the present, challenging classical causality and introducing a novel physical interpretation of temporal determinacy.

Vesselin Petkov

Robert Oeckl

We provide a framework and explicit construction for the regularized measurement of a large class of spacetime-localized observables in bosonic quantum field theory. The measurements fully satisfy relativistic causality and causal transparency, i.e., avoid unphysical superluminal signaling. We show explicitly how the measurement of time-extended observables back-reacts on itself and induces correlations between other measurements in its causal future. Our framework is fully compositional in spacetime and extends previous results on the measurement of instantaneous observables.