# Spacetime from Entanglement: Is the Universe Built Like a Quantum Error-Correcting Code? - Link: https://jarlhalla.com/spacetime-from-entanglement-is-the-universe-built-like-a-quantum-error-correcting-code/ - Published: 2026-08-12T12:37:30+02:00 - Author: knoksen ## How Quantum Information Is Reshaping Our Understanding of Geometry, Gravity, and the Architecture of Reality ### Abstract For more than a century, spacetime has occupied a foundational role in physics. General relativity describes gravity not as a conventional force but as the curvature of spacetime itself, while quantum field theory ordinarily assumes a spacetime background on which quantum fields propagate. Yet some of the most influential developments in quantum gravity now suggest that this hierarchy may be reversed: spacetime might not be fundamental at all. Instead, geometry may emerge from a deeper quantum-information structure, particularly from patterns of quantum entanglement. The strongest realization of this idea comes from holography and the Anti-de Sitter/ conformal field theory correspondence (AdS/CFT). The Ryu–Takayanagi relation connects the entanglement entropy of a region in a boundary quantum theory to the area of a geometric surface in a higher-dimensional gravitational spacetime. Subsequent developments connected changes in entanglement with Einstein’s equations, interpreted bulk locality through quantum error correction, and showed that information apparently located inside a gravitational region may be redundantly encoded across a lower- dimensional quantum system. Tensor networks, entanglement wedges, quantum extremal surfaces, and black-hole information theory have subsequently transformed this insight into a broad research programme. This article traces the historical evolution of the idea, explains its technical foundations in language intended for professionals and engineers, assesses its current scientific status, examines practical applications in quantum computing and numerical physics, and explores future directions. The central conclusion is deliberately precise: modern research provides substantial theoretical evidence that **certain semiclassical spacetimes can be encoded in quantum entanglement**, especially within holographic systems. It does **not** yet demonstrate that the spacetime of our observable universe is literally generated by entanglement, nor that nature implements one specific quantum error-correcting code. Nevertheless, the convergence of gravity, information theory, geometry and quantum computation represents one of the deepest conceptual shifts in contemporary theoretical physics. **Keywords:** emergent spacetime; quantum entanglement; AdS/CFT; holography; Ryu– Takayanagi; quantum gravity; quantum error correction; entanglement wedge; tensor networks; black holes; quantum information; quantum extremal surfaces; holographic codes; spacetime geometry --- # 1. Introduction: What If Space Is Not the Stage? Engineers are accustomed to distinguishing between a system’s physical implementation and its higher-level behaviour. A finite-element mesh is not the structure it represents. A data model is not the physical asset represented by the model. A distributed computer service may appear to occupy one logical address even though its information is redundantly encoded across many machines. At different abstraction levels, radically different descriptions of the same system can all be valid. Modern quantum gravity is beginning to suggest that spacetime itself may require a similar change of abstraction. Einstein’s general theory of relativity transformed space and time from a fixed Newtonian arena into a dynamical geometric structure. Matter and energy influence spacetime curvature, while curvature determines how matter and radiation move. This picture has been spectacularly successful, from gravitational lensing and black holes to gravitational waves and relativistic corrections in satellite navigation. Yet general relativity is a classical theory. Quantum mechanics describes nature at microscopic scales, and attempts to combine the two frameworks expose deep conceptual problems. Black-hole evaporation, cosmological singularities and the Planck regime all indicate that the smooth spacetime manifold of relativity cannot simply be assumed to remain fundamental at arbitrarily short scales. A radical alternative has therefore emerged: perhaps quantum gravity should not begin by quantizing spacetime geometry itself. Perhaps geometry arises only approximately from more primitive quantum degrees of freedom. One candidate for that deeper substrate is **quantum entanglement**. The idea became quantitatively powerful after Ryu and Takayanagi discovered in 2006 that, within AdS/CFT, the entropy measuring entanglement in a boundary quantum system can be computed geometrically from the area of a surface in the higher-dimensional gravitational spacetime. Their formula connected two apparently different concepts— information and geometry—with remarkable precision (Ryu & Takayanagi, 2006). The connection became even deeper. Van Raamsdonk argued that reducing entanglement between parts of the underlying quantum system causes the corresponding spacetime regions to become geometrically disconnected. In this perspective, entanglement is not merely something that happens _inside_ space; it may be part of what holds space together (Van Raamsdonk, 2010). Later work demonstrated that the equations governing gravitational perturbations can themselves be related to entanglement constraints in the boundary quantum theory. Faulkner, Guica, Hartman, Myers and Van Raamsdonk showed that, for appropriate holographic conformal field theories, the first law of entanglement leads to the linearized Einstein equations in the bulk (Faulkner et al., 2014). Another surprising connection followed. Almheiri, Dong and Harlow demonstrated that the peculiar redundancy of bulk information in holography resembles **quantum error correction**. Bulk operators can have multiple equivalent representations on different parts of the boundary, much as logical quantum information can survive the loss or corruption of some physical qubits (Almheiri et al., 2015). The resulting hypothesis is extraordinary but must be phrased carefully: **Spacetime may be an emergent representation of quantum information whose entanglement structure determines, or at least strongly constrains, geometry.** This article examines how strong that statement actually is. For professionals and engineers, the topic matters beyond abstract philosophy. It represents a striking example of cross-disciplinary systems thinking. Concepts from coding theory, network optimization, information entropy, renormalization, geometry and distributed information are converging on some of the hardest problems in fundamental physics. The same mathematical structures developed to understand black holes are now influencing quantum-computer architecture and error correction, while experimental quantum processors are beginning to simulate simplified holographic systems. The challenge is to distinguish genuine scientific results from attractive metaphor. The universe has not been shown to be a computer simulation. A laboratory has not created an astrophysical wormhole. Entanglement alone has not yet been demonstrated to generate our cosmological spacetime. What has been demonstrated is subtler—and arguably more interesting. --- # 2. Defining the Scope: What Does “Spacetime from Entanglement” Mean? The phrase _spacetime from entanglement_ covers several related but distinct claims. At the strongest speculative level, it could mean that space, time, gravity and locality are entirely emergent phenomena arising from an underlying quantum information system with no fundamental spacetime description. At a more controlled level, which is where most rigorous work exists, it means that in holographic dualities a higher-dimensional gravitational geometry can be encoded by the quantum state of a lower-dimensional, non-gravitational theory. The pattern of entanglement within that quantum state is deeply related to geometric quantities in the gravitational description. These statements should not be conflated. AdS/CFT provides the best-developed theoretical laboratory. Anti-de Sitter space is a spacetime with negative cosmological curvature and is not a direct description of our accelerating universe. Our large-scale universe is closer to de Sitter geometry, with positive cosmological constant. Extending holographic principles to realistic cosmology remains an open problem. Consequently, the scientifically defensible position in 2026 is: **Established within specific theoretical frameworks:** entanglement entropy and bulk geometry are quantitatively linked in holographic theories. **Strongly supported theoretically:** quantum-error-correcting structures explain important aspects of bulk locality and redundant encoding. **Under active study:** the extent to which Einstein gravity can be derived from information-theoretic principles. **Open:** whether the spacetime of our universe fundamentally emerges from entanglement. **Speculative:** that reality literally runs as a conventional digital quantum computer or that known quantum error-correcting codes constitute the microscopic architecture of nature. Maintaining these distinctions is essential because holography has generated unusually powerful mathematics, but mathematical coherence is not equivalent to direct empirical confirmation. --- # 3. Historical Context: From Geometry to Information ## 3.1 Einstein Makes Geometry Dynamical The first conceptual revolution was Einstein’s general relativity. Rather than treating gravitational attraction as a force propagating through a fixed background, general relativity identifies gravitational phenomena with spacetime curvature. This made geometry dynamical—but geometry remained fundamental. Quantum theory developed along a different route. Quantum field theory describes particles as excitations of underlying quantum fields. These fields are usually formulated on a spacetime background whose causal and geometric structure is supplied independently. That division works exceptionally well at accessible energies. It becomes problematic where quantum effects and strong gravity must both be considered. Black holes provided the first major clue that the division between geometry and information might be incomplete. ## 3.2 Black-Hole Entropy Changes the Question The study of black-hole thermodynamics in the 1970s revealed an unexpected relationship between information and area. Black-hole entropy is proportional not to the volume enclosed by the horizon, but to the horizon’s surface area. This result suggested that the maximum information content associated with a gravitating region might scale with area rather than volume. Gerard ‘t Hooft developed this observation into a dimensional-reduction perspective on quantum gravity, arguing that a gravitational system might be describable by degrees of freedom living on a lower-dimensional structure. Leonard Susskind subsequently formulated the idea explicitly as the **holographic principle**: a volume of space might be fully represented by information associated with its boundary (‘t Hooft, 1993; Susskind, 1995). The name “holographic” is suggestive but imperfect. Ordinary optical holography stores information about a three-dimensional image on a two-dimensional surface. Quantum-gravitational holography is much more profound: it proposes an equivalence between theories with different apparent dimensionalities. ## 3.3 Maldacena Gives Holography a Concrete Framework In 1997, Juan Maldacena proposed the correspondence now known as AdS/CFT. In its canonical forms, a theory containing gravity in an Anti-de Sitter bulk is dual to a conformal quantum field theory without gravity defined on its lower-dimensional boundary. The word **dual** is crucial. One description is not merely an approximation of the other. The conjecture states that they encode the same underlying physics through different variables. A gravitational problem in the bulk can therefore, in principle, be translated into a quantum-field-theory problem on the boundary and vice versa. Maldacena’s proposal produced the first highly developed realization of the holographic principle in string theory and became one of the central frameworks of modern quantum-gravity research (Maldacena, 1998). For an engineer, an imperfect but useful analogy is model transformation. Consider two mathematically equivalent formulations of a physical system—one expressed in displacement variables, another in stress functions. Neither is merely an image of the other; each provides a different computational representation of the same physical structure. AdS/CFT proposes an equivalence vastly more radical: a theory with gravity and an extra spatial dimension corresponds to a lower-dimensional theory with no dynamical gravity. But one critical question remained. If the boundary contains no explicit bulk dimension, **where does the extra spatial dimension come from?** Entanglement supplied a remarkable answer. --- # 4. The Ryu–Takayanagi Breakthrough: Turning Entropy into Area Consider a quantum system divided into a region (A) and its complement. Even if the entire system is in a pure quantum state, measurements restricted to region ( A) can exhibit uncertainty because (A) is entangled with degrees of freedom outside it. The reduced density matrix is [ \rho_A=\mathrm{Tr}_{\bar A}\rho,] and its von Neumann entanglement entropy is [ S(A)=-\mathrm{Tr}(\rho_A\ln\rho_A).] This quantity measures how much quantum information is shared across the partition. Ryu and Takayanagi discovered that in static holographic systems this information- theoretic quantity has a geometric representation: [ S(A)=\frac{\mathrm{Area}(\gamma_A)}{4G_N},] where (\gamma_A) is a minimal bulk surface anchored to the boundary of region (A), and (G_N) is Newton’s gravitational constant in the bulk theory. The formula reproduces known entanglement-entropy results in appropriate conformal field theories and closely resembles the Bekenstein–Hawking entropy relation for black holes (Ryu & Takayanagi, 2006). This equation was conceptually transformative. The left side contains **quantum information**. The right side contains **spacetime geometry**. It says, within its domain of validity, that measuring entanglement in the boundary theory determines an area in the gravitational spacetime. That is far stronger than a qualitative analogy. ## 4.1 From Static to Dynamical Spacetime The original Ryu–Takayanagi formula applied most directly to static geometries. Hubeny, Rangamani and Takayanagi subsequently proposed a covariant extension suitable for time-dependent situations. Instead of a spatial minimal surface, one considers an appropriate extremal codimension-two surface in the dynamical bulk. The HRT prescription made entanglement geometry relevant to collapsing matter, evolving quantum states and black-hole spacetimes rather than only static configurations ( Hubeny et al., 2007). The conceptual implication is important. If geometry were merely correlated with one special class of static entanglement patterns, its significance might be limited. Covariant generalizations indicate that the connection persists when spacetime itself evolves. ## 4.2 A Network-Theory Interpretation: Bit Threads Freedman and Headrick later reformulated the Ryu–Takayanagi relation using a max- flow/min-cut construction. Instead of describing entanglement through a minimal surface, one can describe it using bounded, divergenceless flows through the bulk—often visualized as **bit threads**. Entanglement entropy corresponds to the maximum possible flux of these threads through the boundary region. The mathematical structure is closely related to network optimization and the max-flow/min-cut theorem (Freedman & Headrick, 2017). This formulation is particularly intuitive for engineers. Imagine that entanglement capacity is represented by bounded information channels crossing the bulk. The Ryu–Takayanagi surface becomes analogous to the minimum-capacity cut that constrains the maximum information flow. This does **not** imply that literal microscopic wires run through spacetime. Bit threads are an alternative mathematical representation. But they reveal how deeply network theory, information flow and geometry are becoming intertwined in gravitational physics. --- # 5. Van Raamsdonk’s Insight: Entanglement as the Connectivity of Space A decisive conceptual step came from asking a simple question: What happens to the bulk geometry if entanglement in the boundary state is systematically removed? Mark Van Raamsdonk studied entangled states associated with connected holographic spacetimes and argued that decreasing entanglement causes the corresponding regions of spacetime to separate. In the limit of vanishing entanglement, a connected geometry can pinch apart into disconnected components (Van Raamsdonk, 2010). The result motivates a powerful picture: **Entanglement may act as part of the connective tissue of emergent geometry.** This should not be interpreted as saying that any pair of entangled particles creates a macroscopic bridge between them. The statement concerns highly structured many- body states in holographic theories. Geometry appears to depend not merely on the _amount_ of entanglement but on its complete organization across many spatial scales. That distinction is critical. A building cannot be reconstructed from the quantity of steel it contains. One needs connectivity, topology, geometry, boundary conditions and material distribution. Similarly, a spacetime is not determined by a single entropy number. The full pattern of correlations across subsystems carries the relevant information. This insight naturally led researchers toward tensor networks. --- # 6. Tensor Networks: A Computational Sketch of Emergent Space Tensor networks were originally developed as efficient mathematical descriptions of highly entangled quantum many-body systems. Rather than explicitly storing exponentially many amplitudes, a quantum state is decomposed into interconnected tensors whose graph structure captures relevant entanglement. Brian Swingle recognized that the multiscale entanglement renormalization ansatz, or MERA, has a geometry strikingly reminiscent of a discretized slice of Anti-de Sitter space. Renormalization organizes information by length scale, and the network introduces an additional direction corresponding approximately to scale. The deeper one moves into the network, the more coarse-grained the description becomes (Swingle, 2012). In AdS/CFT, something similar occurs: the radial bulk direction is associated with energy or renormalization scale in the boundary theory. Thus a new engineering-like picture emerges. A boundary quantum state can be represented as a multilevel information-processing network. The connectivity of this network defines an effective higher-dimensional geometry. Short-range correlations live near one layer; progressively larger-scale information occupies deeper layers. The geometry is therefore not inserted as an independent background. It emerges from how quantum information is organized by scale. This remains a model rather than a literal derivation of physical spacetime. Real AdS/CFT is substantially richer than simple tensor networks. Nevertheless, tensor- network constructions provide tractable laboratories in which entanglement, geometry and information recovery can all be calculated. And these networks led directly to one of the most surprising developments in the entire subject. --- # 7. Spacetime as a Quantum Error-Correcting Code ## 7.1 The Bulk Reconstruction Problem If information about a higher-dimensional bulk is encoded on a lower-dimensional boundary, how is a local object in the bulk represented? One might expect each bulk point to correspond to one specific collection of boundary degrees of freedom. That expectation turns out to be too simple. In AdS/CFT, the same bulk operator may be reconstructed from different boundary regions. This apparent redundancy initially seemed paradoxical. If two distinct regions can represent the same bulk variable, where is the information actually located? Almheiri, Dong and Harlow recognized that the structure resembles **quantum error correction** (Almheiri et al., 2015). In an ordinary classical system, information is often tied to physical locations. Destroy the storage device and the information disappears. Quantum error-correcting codes work differently. A logical qubit is encoded nonlocally into correlations among multiple physical qubits. No single physical qubit necessarily contains the complete logical state. The information survives certain erasures because it is distributed through a protected subspace. Holographic bulk information appears to behave in an analogous way. ## 7.2 The HaPPY Code Pastawski, Yoshida, Harlow and Preskill turned the idea into a concrete tensor-network model in 2015. Their holographic quantum error-correcting construction—commonly known as the **HaPPY code**—places tensors on a hyperbolic geometry. Logical degrees of freedom occupy the interior, while physical degrees of freedom appear on the boundary. Bulk information can be reconstructed from selected boundary regions, and the model reproduces important qualitative and, in specific cases, exact features associated with the Ryu–Takayanagi relation (Pastawski et al., 2015). The code is a toy model, not a complete microscopic construction of AdS/CFT. But it demonstrates something extraordinary: A network that is fundamentally an information-encoding system can simultaneously exhibit an effective geometry, local bulk variables, boundary reconstruction and an area-like entanglement law. For systems engineers, the analogy to fault-tolerant distributed architectures is difficult to miss. The interior is like a **logical layer**. The boundary is like a **physical implementation layer**. Local bulk information can survive the loss of some boundary data because it has been redundantly encoded. Geometry determines which boundary subsets can reconstruct which interior information. Yet there is a crucial difference from conventional redundancy. Holographic encoding is not simply copying data. The no-cloning theorem prohibits arbitrary copying of unknown quantum information. Redundancy appears through nonlocal quantum correlations and operator-algebraic encoding. ## 7.3 Entanglement-Wedge Reconstruction The next step made the idea mathematically sharper. For a chosen boundary region (A), holography associates a bulk region known as its** entanglement wedge**. Dong, Harlow and Wall demonstrated that bulk operators inside this wedge can be reconstructed using operators acting only on the corresponding boundary region under appropriate holographic conditions (Dong et al., 2016). This provides a remarkably geometric interpretation of recoverability. The question > “Which information can this subsystem access?” becomes linked to > “Which region of bulk spacetime belongs to its entanglement wedge?” Information accessibility and spatial geometry become two representations of the same structure. For engineers, this is perhaps the cleanest route to understanding why the phrase _spacetime as quantum error correction_ is more than metaphor. A geometry effectively specifies the **reconstruction map**. --- # 8. From Entanglement to Einstein’s Equations Connecting entanglement to geometric surfaces is impressive. An even deeper question is whether gravitational **dynamics** can emerge from entanglement principles. Quantum information contains an analogue of the first law of thermodynamics. For sufficiently small perturbations of a reference state, [ \delta S_A=\delta\langle H_A\rangle,] where (H_A) is the modular Hamiltonian associated with region (A). Faulkner and colleagues investigated this identity in holographic conformal field theories. For small perturbations around the vacuum state, imposing the entanglement first law for all appropriate boundary regions corresponds in the gravitational description to satisfying the linearized Einstein equations around Anti-de Sitter space (Faulkner et al., 2014). This result deserves careful interpretation. It does not yet prove that all of general relativity follows universally from entanglement. It does show that, within an important class of holographic systems, a fundamental gravitational field equation is encoded in consistency conditions on boundary quantum information. That reverses the conventional explanatory hierarchy. Instead of: **spacetime geometry → quantum fields and their entanglement** one can contemplate: **quantum state + entanglement constraints → effective spacetime geometry + gravitational dynamics** This inversion is one reason the field has become central to modern quantum-gravity research. --- # 9. Quantum Corrections: From RT Surfaces to Quantum Extremal Surfaces The classical Ryu–Takayanagi area term is only the leading contribution in a semiclassical gravitational expansion. Quantum fields in the bulk themselves possess entanglement. Faulkner, Lewkowycz and Maldacena showed how bulk quantum entanglement corrects the classical area prescription. Engelhardt and Wall subsequently formulated the more general concept of a **quantum extremal surface**. The relevant generalized entropy takes the schematic form # [⏎ S_{\mathrm{gen}} \frac{\mathrm{Area}}{4G_N} +S_{\mathrm{bulk}},] and one extremizes the combined quantity rather than the area alone (Engelhardt & Wall, 2015). Conceptually, this is important because the geometry cannot be separated cleanly from the quantum information of matter fields. The first term is geometric. The second is quantum informational. The physically relevant surface depends on both. This synthesis became crucial in the black-hole information problem. --- # 10. Black Holes, Islands, and the Page Curve Stephen Hawking’s semiclassical calculation implied that black holes radiate thermally. If a black hole forms from a pure quantum state and evaporates completely into perfectly thermal radiation, information appears to be destroyed, conflicting with ordinary unitary quantum mechanics. The modern holographic approach reframed this question in terms of entanglement. For a unitary evaporation process, the entropy of Hawking radiation should initially rise as radiation becomes entangled with the remaining black hole. After the **Page time**, information begins to emerge and the radiation entropy should decrease, eventually returning toward zero if the final global state is pure. This behaviour is the **Page curve**. Calculations involving quantum extremal surfaces and entanglement wedges revealed new regions called **islands**. After the Page transition, part of what semiclassical reasoning would call the black-hole interior can belong to the entanglement wedge of the Hawking radiation. Penington, and independently Almheiri, Engelhardt, Marolf and Maxfield, showed how such entanglement-wedge transitions reproduce the expected Page-curve behaviour in controlled models (Almheiri et al., 2019; Penington, 2020). The interpretation is profound. Information that appears geometrically to reside _inside_ the black hole may, in the more fundamental quantum description, already be encoded in the radiation outside. Once again, naive geometric locality ceases to be the fundamental organizing principle. Quantum information becomes primary. These calculations have substantially advanced theoretical understanding of black- hole information, but they do not mean that the astrophysical black-hole information paradox has been experimentally resolved. The calculations are strongest in controlled holographic and lower-dimensional gravitational models. --- # 11. Current Relevance in 2026 By 2026, “spacetime from entanglement” is no longer one isolated conjecture. It sits at the intersection of several active research programmes: holography, quantum error correction, black-hole information, tensor networks, quantum simulation, metric reconstruction and quantum complexity. The field has also moved beyond purely formal manipulations. ## 11.1 Geometry Reconstruction from Entanglement Data One active direction treats the relationship almost as an inverse engineering problem: **Given quantum-information data on the boundary, how much of the bulk metric can be reconstructed?** Recent work has investigated relationships between conditional mutual information and radial bulk geometry, proposing methods for reconstructing metric information from patterns of boundary entanglement. Such approaches remain model-dependent and require gauge choices, but they illustrate the direction of travel: researchers are increasingly treating geometry as something potentially inferable from information- theoretic observables rather than assumed in advance. The analogy to inverse problems in engineering is strong. In structural health monitoring, internal properties are inferred from external response measurements. In tomography, an interior distribution is reconstructed from boundary or projection data. In holography, one asks whether an interior spacetime can be reconstructed from quantum observables associated with its boundary. The mathematics is very different, but the systems logic is recognizably similar. ## 11.2 Quantum Computers as Holographic Laboratories A major opportunity comes from programmable quantum processors. In 2022, Jafferis and collaborators implemented a small quantum system inspired by a traversable-wormhole model using nine qubits. The experiment reproduced selected dynamics associated with a simplified holographic model. It did **not** open a wormhole in laboratory spacetime. Instead, a quantum processor simulated the dynamics of a model whose alternative gravitational description contains a traversable wormhole( Jafferis et al., 2022). That distinction is essential. The experiment is analogous to simulating fluid dynamics on a computer: vortices in the simulation do not mean water is physically flowing through the processor. Nevertheless, if holographic duality is valid, such simulations provide a possible experimental route for investigating quantum systems with gravitational dual interpretations. The field has continued advancing. A peer-reviewed 2026 experiment simulated a sparse Sachdev–Ye–Kitaev system with 24 Majorana fermions mapped to 12 system qubits plus an ancilla on a trapped-ion processor. The researchers observed the decay of a Loschmidt amplitude over a useful dynamical regime and analysed resource requirements for larger simulations. They explicitly cautioned that the experiment was not intended as a probe of a realistic gravitational dual; its value lies in demonstrating increasingly capable simulation of strongly interacting systems closely connected to holographic research (Granet et al., 2026). An even more direct connection to holographic error correction appeared in July 2026. Steiner and collaborators reported an experimental implementation of holographic pentagon and heptagon codes on a trapped-ion processor. Their preprint describes tests of bulk logical-qubit recovery from boundary degrees of freedom, entanglement structure, error detection and logical operations. Because the result was a recent preprint at the time of writing, it should be regarded as emerging rather than settled experimental evidence. Crucially, the experiment tests properties of **holographic quantum codes**, not the proposition that physical spacetime is itself such a code( Steiner et al., 2026). --- # 12. Practical Applications For a theory concerned with the foundations of spacetime, “practical application” requires careful definition. No civil engineer will design a bridge using AdS/CFT, and no telecommunications network currently requires a quantum-extremal-surface calculation. Nevertheless, the research has already produced practical mathematical and technological spillovers. ## 12.1 Quantum Error Correction The most obvious application is quantum computing. Holographic models helped physicists understand encoding in which logical information is distributed across a boundary, recoverable from multiple overlapping regions and protected against certain erasures. The HaPPY code itself is not expected to replace leading surface-code architectures directly. Its importance is conceptual and mathematical. It provides an explicit environment for studying subsystem recovery, logical-operator redundancy and relations between code geometry and information accessibility. The cross-pollination works both ways. Quantum information theory helps explain holography, while quantum-gravity-inspired structures generate new classes of quantum codes and recovery problems. This is a recurring pattern in fundamental research: tools developed for problems far removed from immediate engineering application later become useful in technology. ## 12.2 Tensor-Network Simulation of Many-Body Systems Tensor networks provide highly efficient representations of certain structured quantum states. Their importance extends far beyond gravity. They are central tools in condensed- matter physics, quantum chemistry, quantum algorithms and numerical studies of strongly correlated systems. The holographic interpretation adds geometric intuition to the hierarchy of correlations represented by these networks. Entanglement scale becomes associated with network depth, and coarse-graining acquires a geometric interpretation. This does not make every tensor network a model of spacetime. Instead, holography provides another framework for understanding why geometrical representations can emerge naturally when complex correlation structures are organized across scale. ## 12.3 Network Optimization and Bit Threads The bit-thread reformulation of holographic entanglement uses a continuum counterpart of max-flow/min-cut optimization. For engineers familiar with traffic flow, electrical networks, communication capacity or supply-chain bottlenecks, the mathematical resemblance is striking. The maximum information-like flux through a region is constrained by a minimum cut, while the geometry determines available flow configurations (Freedman & Headrick, 2017). Again, bit threads should not be mistaken for a proposed communications infrastructure inside spacetime. Their value is that mature mathematical ideas from optimization theory become a language for quantum gravity. ## 12.4 Quantum Simulation of Strongly Coupled Physics Many strongly interacting quantum systems are notoriously difficult to simulate on classical computers because their state spaces grow exponentially. The SYK family of models is particularly interesting because it combines quantum chaos, strong interactions and connections with simple gravitational theories. The 2026 trapped-ion results therefore matter even independently of quantum gravity. They provide a benchmark for simulating nonlocal, strongly interacting quantum dynamics on programmable hardware (Granet et al., 2026). As quantum hardware improves, researchers may increasingly treat gravitationally inspired models as demanding test cases for quantum processors. Thus fundamental gravity research can become a source of quantum-computing benchmarks. ## 12.5 Information-Theoretic Diagnostics of Physical Systems Concepts such as mutual information, relative entropy, modular Hamiltonians, scrambling and recovery channels now move fluidly among high-energy physics, statistical mechanics, condensed matter and quantum information. This cross-domain transfer may ultimately prove more technologically significant than any single speculative theory of emergent spacetime. The central engineering lesson is that **information structure can sometimes expose physical organization more clearly than microscopic coordinates do**. That insight is already familiar in control theory, digital twins, systems engineering and network science. Quantum gravity pushes it to an extreme: perhaps even the coordinates and geometry in which physics appears to occur are emergent descriptors of a deeper information architecture. --- # 13. Is the Universe Literally a Quantum Error-Correcting Code? The short answer is: **We do not know, and taken literally the claim is too strong.** The phrase is scientifically useful because holographic systems display mathematical structures characteristic of quantum error correction. It becomes misleading if interpreted as meaning that researchers have discovered a hidden array of physical qubits underneath spacetime. The known correspondence is more abstract. A bulk effective theory contains local fields and geometry. The boundary description encodes the same physics nonlocally. Information about bulk regions is redundantly represented across appropriate boundary subregions. Quantum error-correction theory provides the correct mathematics for describing that redundancy. So the stronger and more accurate claim is: **Semiclassical gravitational locality behaves as though it is protected by an underlying quantum error-correcting structure.** That is already remarkable. It may help explain why smooth spacetime is robust even though its microscopic quantum description could be radically nonlocal. Think of the difference between source code and the interface of a robust distributed application. A user experiences stable objects and local interactions, while the physical storage of information underneath may be fragmented, redundant and dynamically reconstructed. In holographic quantum gravity, familiar local spacetime may similarly be an effective interface. But this remains an analogy until a complete theory specifies the actual microscopic degrees of freedom of our universe. --- # 14. The Hard Problems That Remain ## 14.1 AdS Is Not Our Universe The most developed holographic framework concerns Anti-de Sitter spacetime. Cosmological observations indicate that our universe currently undergoes accelerated expansion, corresponding more closely to a positive cosmological constant and de Sitter-like geometry. A complete holographic description of realistic de Sitter cosmology remains unresolved. This is arguably the single greatest limitation on sweeping claims that AdS/CFT has already explained the emergence of _our_ spacetime. ## 14.2 Time May Be Harder Than Space Many tensor-network models provide intuitive pictures of emergent **spatial** geometry. Emergent time is more difficult. Time in quantum mechanics ordinarily parametrizes evolution, whereas time in general relativity is part of dynamical spacetime geometry. A theory in which both space and time emerge from non-spatiotemporal quantum structure must explain causal order, Lorentz symmetry, clocks, dynamics and the arrow of time. No universally accepted derivation currently accomplishes all of this. ## 14.3 Entanglement Is Probably Not Sufficient by Itself Saying “spacetime comes from entanglement” can create the impression that entanglement alone uniquely determines geometry. That is too simplistic. Researchers require additional ingredients: the underlying Hilbert-space structure, state, operator algebra, symmetry, dynamics, entanglement spectrum and often assumptions about large-(N) limits and semiclassical behaviour. Different quantum states may possess similar entropy data without representing identical geometries. Therefore the real question is not merely: **How much entanglement exists?** It is: **What complete structure of quantum information, dynamics and constraints produces a local semiclassical spacetime?** ## 14.4 The Emergence of Matter A successful theory must explain more than geometry. Our universe contains gauge fields, fermions, symmetry breaking, particle masses and the Standard Model. If spacetime emerges from a deeper quantum-information architecture, matter and gauge interactions must either emerge alongside it or be encoded consistently within the same microscopic framework. String theory provides one broader environment in which geometry, gravity and gauge fields can arise together, but extracting a unique realistic low-energy universe remains a major unresolved problem. ## 14.5 Experimental Falsifiability The deepest challenge remains empirical. AdS/CFT is extraordinarily well supported as a theoretical duality across many examples, but there is no direct experimental observation showing that our spacetime emerges from quantum entanglement. Quantum processors can implement holographically inspired Hamiltonians and codes. Those experiments test quantum mechanics, code properties and simulated model dynamics. They do not yet constitute observations of Planck-scale spacetime microstructure. The field therefore remains primarily one of theoretical physics rather than experimentally confirmed quantum gravity. --- # 15. Future Implications ## 15.1 Quantum Gravity May Become an Information Science The most important long-term shift may be methodological. Historically, physicists attempted to understand fundamental reality primarily through particles, fields, forces and symmetries. Quantum gravity increasingly introduces another vocabulary: **entropy, information, entanglement, coding, complexity and computation.** This does not replace traditional physics. Instead, information-theoretic quantities may become as fundamental to quantum gravity as energy and momentum are to classical mechanics. The Ryu–Takayanagi formula is perhaps the clearest symbol of this transformation: an entropy becomes an area. ## 15.2 Better Quantum Computers May Become Quantum-Gravity Simulators The progression from nine-qubit holographically inspired wormhole dynamics in 2022 to larger sparse-SYK simulations in 2026 illustrates a possible trajectory. As hardware improves, quantum processors could simulate increasingly complex strongly interacting systems whose low-energy descriptions have gravitational interpretations. Future experiments could explore scrambling, thermalization, operator growth, teleportation protocols, black-hole-like information recovery and holographic codes at scales inaccessible to classical simulation. Such machines would not need to reproduce astrophysical gravity directly. They could function as **analogue or dual laboratories** for mathematical structures relevant to quantum gravity. This would resemble established analogue-gravity research, where laboratory systems reproduce selected equations or kinematic phenomena associated with horizons and curved spacetime without generating real astrophysical gravitational fields. ## 15.3 Geometry Could Become an Emergent Data Product A particularly intriguing future research direction is automatic reconstruction of geometry from quantum data. Instead of specifying a metric (g_{\mu\nu}) and calculating observables, one could imagine measuring or computing a sufficiently rich set of entanglement quantities and reconstructing the effective geometry that best explains them. Recent metric-reconstruction proposals based on entanglement data illustrate early versions of this inverse programme. Machine learning may eventually contribute to such work by learning maps between high-dimensional correlation data and candidate geometric descriptions. This would invert the conventional computational pipeline: **Traditional gravitational modelling** geometry → fields → observables could be complemented by **information-first reconstruction** quantum correlations → geometry → effective gravitational description. For professionals familiar with digital twins, inverse modelling and system identification, the conceptual similarity is compelling. ## 15.4 Quantum Error Correction Could Explain Semiclassical Robustness One persistent question in quantum gravity is why smooth classical spacetime is so stable. Quantum degrees of freedom are intrinsically noisy, nonlocal and subject to fluctuations, yet macroscopic geometry appears extraordinarily robust. Holographic quantum-error-correction ideas suggest a possible explanation. Local semiclassical observables may correspond to protected logical information rather than fragile microscopic variables. If so, spacetime locality could be analogous to a fault-tolerant code property. Microscopic disturbances would not necessarily destroy the emergent geometry because geometric information would be redundantly encoded. This remains a theoretical interpretation rather than an established description of nature, but it offers a powerful conceptual route toward understanding the classical limit. ## 15.5 Black-Hole Interiors May Become Problems of Decoding The black-hole information problem is increasingly being reformulated as a reconstruction problem. Which subsystem contains the information? When can it be recovered? Which decoding operation reconstructs a bulk operator? How does the reconstruction region change during evaporation? Entanglement wedges and islands transform these questions into a combination of geometry and quantum information. Future progress may therefore make black-hole physics look increasingly like advanced coding theory. This would have been difficult to imagine when the information paradox was first formulated. --- # 16. A Systems-Engineering Interpretation For engineers, the deepest value of this research may lie in the architectural principle it suggests. Consider four layers. ### Layer 1: Microscopic quantum state At the deepest level lies an enormous quantum state characterized by amplitudes, correlations and entanglement. ### Layer 2: Encoding structure The information is organized nonlocally. Logical variables become recoverable from overlapping subsets of more microscopic degrees of freedom. ### Layer 3: Emergent geometry The pattern of recoverability and entanglement admits a geometric description. Distances, areas, connectivity and locality become meaningful. ### Layer 4: Classical spacetime physics At sufficiently large scales, the geometry obeys approximately classical gravitational equations and matter propagates locally through the emergent spacetime. This resembles hierarchical modelling in complex engineered systems. The key difference is staggering in scale: in this hypothesis, **physical space itself belongs to the higher-level model**. Coordinates would not be fundamental addresses. Distances would not be primitive inputs. Locality would not necessarily exist microscopically. They would be emergent properties of the information architecture. That perspective does not diminish spacetime’s reality. Temperature is emergent from microscopic statistical mechanics yet perfectly real. Elastic modulus is emergent from atomic interactions yet indispensable in engineering. Fluid pressure is emergent from molecular dynamics yet objectively measurable. Likewise, spacetime could be emergent while remaining the correct physical description at macroscopic scales. “Emergent” does not mean imaginary. It means **dependent on deeper collective structure**. --- # 17. What Would Count as a Major Breakthrough? The field would advance dramatically if researchers achieved several currently missing connections. A compelling microscopic theory would need to reproduce realistic four-dimensional spacetime, approximate Lorentz invariance, matter content, gravitational dynamics and cosmological evolution from an underlying quantum structure. A convincing theory should also explain why our universe occupies its observed state rather than merely constructing many mathematically possible emergent geometries. More decisive experimental progress would require identifying phenomena that distinguish an information-theoretic emergent-spacetime model from competing quantum-gravity theories. Quantum simulators could contribute by testing increasingly sophisticated holographic models and code structures. A July 2026 trapped-ion preprint demonstrating experimental holographic-code behaviour is an important research milestone in that direction, but it remains several conceptual steps removed from testing the microscopic nature of real spacetime. The most transformative result would be a genuine quantitative prediction of an observable phenomenon that is difficult to explain without the emergent-information architecture and can be measured independently in nature. Until then, the programme should be judged by theoretical consistency, explanatory power, mathematical fertility and its ability to generate progressively sharper tests—not by dramatic metaphors. --- # 18. Conclusion: From the Geometry of Matter to the Geometry of Information Physics has repeatedly discovered that structures once regarded as fundamental are emergent. Heat became molecular motion. Material rigidity became collective electromagnetic interactions among atoms. Particles became excitations of quantum fields. General relativity transformed gravity from a force into geometry. Quantum gravity may require one more inversion. Perhaps geometry itself emerges. The strongest evidence for this possibility comes from holography. Maldacena’s AdS/ CFT correspondence demonstrated that gravitational physics can possess an equivalent lower-dimensional quantum description. Ryu and Takayanagi then showed that boundary entanglement entropy maps directly to geometric area. Van Raamsdonk connected entanglement with spacetime connectivity. Faulkner and collaborators linked entanglement constraints to linearized Einstein dynamics. Almheiri, Dong and Harlow recognized quantum-error- correcting structure in bulk reconstruction. Pastawski and collaborators built explicit holographic codes. Quantum extremal surfaces and islands extended the framework into black-hole information. Collectively, these developments have changed the conceptual question facing quantum gravity. The old question was: **How do we quantize spacetime?** The newer question may be: **What quantum-information architecture gives rise to something that looks like spacetime?** That is a profound change. Yet scientific restraint remains essential. The observable universe has not been demonstrated to be a quantum error-correcting code. AdS/CFT does not yet provide a complete holographic model of realistic cosmology. Entanglement is not known to be sufficient by itself to generate space, time, matter and gravity. Laboratory simulations of holographic systems test fascinating quantum models but do not manufacture literal gravitational wormholes. The durable result is more precise. Quantum information and spacetime geometry are not separate subjects in modern theoretical physics. In our best-controlled models of quantum gravity, they are mathematically intertwined. A region’s entropy can determine a surface area. Information recoverability can determine a geometric wedge. Redundant quantum encoding can mimic bulk locality. Entanglement constraints can encode gravitational equations. Black-hole interiors can become questions of information reconstruction. This emerging framework suggests that the universe may be less like a collection of objects placed inside a pre-existing geometric container and more like an enormously complex relational quantum system whose large-scale information structure **is perceived as geometry**. For scientists and engineers, that possibility is especially compelling because it connects two of humanity’s most powerful intellectual frameworks: geometry, which describes structure in space, and information theory, which describes structure in possibility. If the programme ultimately succeeds, spacetime may cease to be the foundation upon which physics is constructed. It may instead become one of physics’ most extraordinary emergent structures. And beneath it may lie not smaller pieces of space, but something conceptually different: **quantum information, organized so precisely that geometry emerges from the pattern.** --- # References Almheiri, A., Dong, X., & Harlow, D. (2015). 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