We show in this pedagogical review that far from being an apparent law of physics that stands by itself, the holographic principle is a straightforward consequence of the quantum information theory of separable systems. It provides a basis for the theories of measurement, time, and scattering. Utilizing the notion of holographic screens, which are information encoding boundaries between physical subsystems, we demonstrate that the physical interaction is an information exchange during which information is strictly conserved. Then we use generalized holographic principle in order to flesh out a fully-general quantum theory of measurement in which the measurement produces finite-resolution, classical outcomes. Further, we show that the measurements are given meaning by quantum reference frames and sequential measurements induce topological quantum field theories. Finally, we discuss principles equivalent to the holographic principle, including Markov blankets and the free-energy principle in biology, multiple realizability and virtual machines in computer science, and active inference and interface theories in cognitive science. This appearance in multiple disciplines suggests that the holographic principle is not just a fundamental principle of physics, but of all of science. Quanta 2022; 11: 72–96.
We show in this pedagogical review that far from being an apparent law of physics that stands by itself, the holographic principle is a straightforward consequence of the quantum information theory of separable systems. It provides a basis for the theories of measurement, time, and scattering. Utilizing the notion of holographic screens, which are information encoding boundaries between physical subsystems, we demonstrate that the physical interaction is an information exchange during which information is strictly conserved. Then we use generalized holographic principle in order to flesh out a fully-general quantum theory of measurement in which the measurement produces finite-resolution, classical outcomes. Further, we show that the measurements are given meaning by quantum reference frames and sequential measurements induce topological quantum field theories. Finally, we discuss principles equivalent to the holographic principle, including Markov blankets and the free-energy principle in biology, multiple realizability and virtual machines in computer science, and active inference and interface theories in cognitive science. This appearance in multiple disciplines suggests that the holographic principle is not just a fundamental principle of physics, but of all of science. Quanta 2022; 11: 72–96.
The measurement problem of quantum theory remains unresolved in terms of how the quantum state of the physical world can be reduced to an observed state of the world. In the conventional formulation of quantum theory, the quantum state of the physical world is understood as an unobserved state of potentiality or a quantum wavefunction that must collapse into an observed state of actuality for the physical world to actually be observed. The unresolved issue of the quantum measurement problem is about the true nature of the observer. This question about the true nature of the observer explodes when we understand the quantum state of the physical world in terms of the holographic principle of quantum gravity, which tells us the fundamental nature of the physical world is quantized bits of information, called qubits, encoded on a holographic screen. The holographic screen in turn can be understood as an event horizon that arises in an observer's accelerated frame of reference. This way of understanding the holographic principle can be understood in terms of matrix models that utilize non-commutative geometry. The holographic principle understood in the context of an observer in an accelerated frame of reference has something important to tell us about the true nature of the observer, which is that every observer is at the center of its own holographic screen that defines its own observable holographic world.
Any interaction between finite quantum systems in a separable joint state can be viewed as encoding classical information on an induced holographic screen. Here we show that when such an interaction is represented as a measurement, the quantum reference frames (QRFs) deployed to identify systems and pick out their pointer states induce decoherence, breaking the symmetry of the holographic encoding in an observer-relative way. Observable entanglement, contextuality, and classical memory are, in this representation, logical and temporal relations between QRFs. Sharing entanglement as a resource requires a priori shared QRFs.
Quantum information has dramatically changed information science and technology, looking at the quantum nature of the information carrier as a resource for building new information protocols, designing radically new communication and computation algorithms, and ultra-sensitive measurements in metrology, with a wealth of applications. From a fundamental perspective, this new discipline has led us to regard quantum theory itself as a special theory of information, and has opened routes for exploring solutions to the tension with general relativity, based, for example, on the holographic principle, on non-causal variations of the theory, or else on the powerful algorithm of the quantum cellular automaton, which has revealed new routes for exploring quantum fields theory, both as a new microscopic mechanism on the fundamental side, and as a tool for efficient physical quantum simulations for practical purposes. In this golden age of foundations, an astonishing number of new ideas, frameworks, and results, spawned by the quantum information theory experience, have revolutionized the way we think about the subject, with a new research community emerging worldwide, including scientists from computer science and mathematics.
It was found, by studying black holes, that the compatibility of the theory of gravity and the laws of quantum mechanics demands that the universe must act like a hologram. That is, all the information inside a region of the universe should be encoded on a so-called holographic screen of one-lesser dimension. This is termed the holographic principle. In a generic spacetime, such as an expanding universe, holographic screens depend on the choice of an observer, which is consistent with the notion that the observer is part of the system in cosmology. In the first part of this dissertation, we study the observer-dependence of holographic screens. This will help us understand how the fundamental description of the universe depends on the choice of the observer. Furthermore, we study the dynamics of the holographic screens and their geometry in the first part of this dissertation.An example where the holographic principle is manifest is the AdS-CFT correspondence. This correspondence connects quantum information quantities, like entanglement and complexity, to geometric quantities, like area and volume, respectively. In the second and the third part of this dissertation, we use the AdS-CFT correspondence as a tool to calculate the entanglement entropy and the computational complexity of a quenched CFT state. Studying the time evolution of the entanglement entropy following a quantum quench teaches us how a CFT state thermalizes. On the other hand, studying the time evolution of the computational complexity allows us to check the validity of various recent conjectures involving black holes and complexity.
Contemporary physics increasingly challenges the classical assumption that information is stored locally within isolated physical systems. Quantum entanglement, relational interpretations of quantum mechanics, spacetime dynamics, and holographic approaches to information all suggest that persistence in nature may be fundamentally relational rather than object-bound. In this paper, we develop a multi-scale interpretive framework in which “memory” is understood not as internal storage within particles or systems, but as the persistence of correlations across quantum states, fields, spacetime geometry, biological organization, and cognitive processes.At the quantum level, relational correlations and entanglement are examined as forms of distributed informational persistence that do not require localized memory carriers. At the spacetime level, curvature and holographic structure are interpreted as persis-tent geometric constraints encoding the historical influence of interactions. Extending beyond physics, biological systems are treated as active stabilizers of relational infor-mation through genetic, metabolic, and neural organization, while consciousness is ex-plored as a higher-order form of integrated relational memory arising from hierarchical informational integration.The framework integrates established theoretical approaches—including relational quantum mechanics, holographic information theory, decoherence theory, and inte-grated information theory—with clearly demarcated speculative hypotheses concerning field-mediated persistence, frequency-based encoding, and cross-scale informational coherence. Throughout, explicit distinctions are maintained between accepted physical formalism, interpretive extension, and speculative proposal.Rather than introducing a new physical theory, this work proposes a unifying concep-tual platform for understanding information persistence across scales. Within this per-spective, memory becomes a distributed structural feature of reality itself: not a proper-ty stored inside isolated objects, but a persistent relational constraint shaping how physical, biological, and cognitive systems evolve through time.
Abstract We introduce novel methods for implementing generic quantum information within a scale‐free architecture. For a given observable system, we show how observational outcomes are taken to be finite bit strings induced by measurement operators derived from a holographic screen bounding the system. In this framework, measurements of identified systems with respect to defined reference frames are represented by semantically‐regulated information flows through distributed systems of finite sets of binary‐valued Barwise‐Seligman classifiers. Specifically, we construct a functor from the category of cone‐cocone diagrams (CCCDs) over finite sets of classifiers, to the category of finite cobordisms of Hilbert spaces. We show that finite CCCDs provide a generic representation of finite quantum reference frames (QRFs). Hence the constructed functor shows how sequential finite measurements can induce TQFTs. The only requirement is that each measurement in a sequence, by itself, satisfies Bayesian coherence, hence that the probabilities it assigns satisfy the Kolmogorov axioms. We extend the analysis too develop topological quantum neural networks (TQNNs), which enable machine learning with functorial evolution of quantum neural 2‐complexes (TQN2Cs) governed by TQFTs amplitudes, and resort to the Atiyah‐Singer theorems in order to classify topological data processed by TQN2Cs. We then comment about the quiver representation of CCCDs and generalized spin‐networks, a basis of the Hilbert spaces of both TQNNs and TQFTs. We finally review potential implementations of this framework in solid state physics and suggest applications to quantum simulation and biological information processing.