In this talk I will present the quantum algorithm for Numerical General Relativity I developed with Prof. Malcolm Fairbairn, and thus show how computationally expensive simulations performed on classical computers such as those of numerical General Relativity (nGR) can be more efficiently tackled by quantum algorithms for solving systems of partial differential equations (pdes), with the possibility to obtain a quantum advantage in terms of computational resources and speed up in runtime with respect to classical counterparts. I will explain the theoretical and practical aspects of this highly interdisciplinary project: from the identification of a suitable numerical General relativity formalism (the WEBB hyperbolic tetrad formalism), to the translation of the system of pdes into a set of quantum computing operations in the form of a quantum walk, the programming of the algorithm components for a gate-based digital quantum computer using the Qiskit software, the choice of a system to test it (Schwarzschild gravitational Quasinormal Modes), and the tests run on both classical simulators and physical IBM quantum computers through the UKRI National Quantum Computing Centre (NQCC) Quantum Access program. I will conclude how this project provides both the first algorithm for nGR for a digital quantum computer, the first application of the WEBB formalism to the study of QNMs, and how it is located in the landscape of Quantum Information applications for Gravity studies.

The traditional laws of black hole mechanics, formulated for stationary Event Horizons, often fall short in practical scenarios where black holes interact with their surroundings and become dynamic. This challenge has been effectively addressed through a quasi-local approach, focusing on trapped surfaces and their boundaries, which provides a more suitable setup for studying non-equilibrium black hole dynamics. In this talk, we outline some recent studies on the dynamical black holes, particularly focusing on Vaidya spacetimes. Further, we elucidate the implications of Conformal Killing Horizons for a wide class of Vaidya-like spacetimes, and discuss their thermodynamic properties.

Black holes pose sharp consistency questions at the interface of gravity, quantum mechanics, and thermodynamics. It is widely believed that resolving problems such as providing a microscopic account of Bekenstein-Hawking entropy, understanding the origin of black hole thermodynamics, and resolving the information paradox posed by Hawking radiation, among others, will provide key insights toward formulating a theory of quantum gravity. In this talk, I discuss a recent proposal of quantum black hole by in terms of a certain large N matrix quantum mechanics. In this model, black hole horizon in general relativity is replaced by a noncommutative fuzzy sphere geometry together with a quantized Fermi sea of states. The Berkenstein-Hawking entropy is understood in terms of the microstate counting of the vacuum degeneracy of the Fermi sea. The Hawking radiation is described consistently in terms of quantum mechanical tunneling of the metastable fuzzy sphere vacua, going beyond the usual semi-classical treatement.

Bosons and fermions are defined by their exchange properties and the underlying symmetries determine the structure of the corresponding state spaces. For two particles there are two possible exchange symmetries, resulting in symmetric or antisymmetric behaviour, but when exploring multiparticle systems also quantum states with chiral symmetries appear. In this work we demonstrate that chiral symmetries lead to extremal forms of quantum entanglement. More precisely, we show that subspaces with this symmetry are highly entangled with respect to the geometric measure of entanglement, leading to observables which can be useful for entanglement characterization. Along the way, we develop a simple method to solve the problem of genuine multiparticle entanglement for unitarily invariant three-particle states and use it to identify genuine multipartite entangled states whose partial transposes with respect to all bipartitions are positive. Finally, we consider generalizations with less symmetry and discuss potential applications.

One of the open issues in cosmology is understanding how cosmological degrees of freedom—such as matter fields and spacetime—have classicalized by the present time, although they are fundamentally quantum in the early universe. In this talk, we discuss the decoherence of an FLRW universe induced through its interaction with quantum scalar fields, such as the inflaton. The quantum state evolution of the scale factor and the scalar field is treated within the Wheeler–DeWitt framework. We consider the macroscopic quantum superposition of two different cosmological constants, and then estimate the decoherence rate of its coherence due to a quantum fluctuation of an inhomogeneous scalar field.

When probing a complex quantum system, one may face the problem that there is no hand-crafted measurement protocol to extract quantities of interest. The field of variational quantum sensing tackles this problem by using quantum machine learning. More specifically, one lets a parameterized quantum circuit interact with the complex quantum system, and tunes the parameters such that the output measurement statistics gives the desired outputs. In my talk, I will present an extension of this approach to quantum field theory on curved spacetime. Here, the probes are modeled as Unruh-DeWitt detectors with tunable free Hamiltonian. Their interaction is mediated by the quantum field which also acts as the investigated complex quantum system. A physical regime is presented for which the quantum field induces a unitary globally entangling gate without acting as a source of noise. The resulting ""hardware efficient ansatz"" is universal for quantum computation.

Semi-classical approaches aim to provide approximate descriptions of fully quantum theories in regimes where one degree of freedom is effectively classical. However, these approaches are also criticised, either because they violate basic physical principles or because they have limited regimes of validity. In this talk, I will show how the standard semi-classical dynamics can be made consistent and given unlimited validity, provided the original quantum dynamics is subject to a specific form of environmental decoherence. Using a simple toy model, I will show how studying the evolution of the fully quantum dynamics in a partial Wigner representation naturally leads to stochastic modifications of the semi-classical equations of motion without the usual approximations. Comparing to the standard semi-classical equations, I will explain how this novel approach can be used to provide a timescale for the validity of the standard semi-classical equations that depends on decoherence rates in the fully quantum theory. This work provides a blueprint for how semi-classical methods in gravity may be pushed beyond the current standard set of tools, and illustrates how recent proposals for hybrid classical-quantum gravity could in principle be reconciled with fully quantum theories of gravity.

Recent cosmological observations increasingly challenge the standard picture of cosmic acceleration, pointing toward an evolving dark-energy sector—possibly with phantom characteristics—and by placing considerable pressure on even the better-theoretically motivated inflationary models. In this talk, I present a new mechanism for cosmic acceleration arising from quantum gravity interactions in (mean-field) Group Field Theories (GFTs). Depending on the interaction type, the resulting cosmological dynamics can either feature a late-time attractor corresponding to a dynamical dark energy phase—often with characteristic phantom behavior, including in models inspired by simplicial gravity—or instead support an early slow-roll inflationary epoch driven by the same underlying quantum-gravitational effects. This emergent inflation, effectively captured by a single-field description, can sustain the required expansion, naturally avoids the graceful exit problem, and appears to transition into a persistent, non-accelerating phase consistent with classical expectations. I conclude by outlining prospects for further developments.

I would like to present our recent numerical results suggesting the phenomenon in the Title based on complex Langevin simulations.

Witnessing gravitationally mediated entanglement (GME) is widely regarded as a decisive indicator of the quantum nature of the gravitational field. However, recent work has questioned the premise that local classical models of gravity are incapable of entangling quantum masses. In this talk, I present an explicit construction of a hybrid classical-quantum theory, formulated as a lattice Yukawa field model, in which a classical gravitational field interacts consistently with quantum matter. Ensuring internal consistency forces the hybrid dynamics to be intrinsically irreversible in both classical and quantum sectors, with the relevant parameters constrained by the “decoherence-diffusion trade-off” — a property often overlooked when discussing GME experiments. This discrete toy model clarifies what proposed entanglement-based experiments can genuinely reveal about the underlying nature of the gravitational interaction, elucidating the conditions for entanglement mediation in the presence of classical degrees of freedom and the role of the decoherence-diffusion trade-off.

Soft modes and boundary degrees of freedom play a central role in quantum gravity, holography, and celestial amplitudes, yet their treatment in asymptotic regimes and finite subregions is often disconnected. In this talk, I present a unified framework that connects these perspectives using a relational description of subsystems in gauge theories. The central idea is that edge modes are dynamical (quantum) reference frames. This viewpoint cleanly separates intrinsic boundary data from extrinsic embedding data, the latter universally extending the phase space through a Goldstone-like corner pair and carrying a symmetry group that governs how soft and hard radiation affect the subregion physics. At the quantum level, this relational structure provides a natural factorisation of the Hilbert space and leads to distillable entanglement entropies. As in gravity, where dynamical reference frames regulate UV divergences, this approach regularises gauge-theoretic entropies without introducing auxiliary edge Hilbert spaces. Different choices of reference frame generate a hierarchy of relational operator algebras. Known constructions appear as symmetry-reduced limits: for example, the electric center arises via projection onto states invariant under corner symmetries. The relational entropies are bounded between these non-distillable limits, providing a coherent organising principle linking soft physics, boundary symmetries, and subsystem information.

This talk will briefly discuss quantum teleportation in qubit systems, particularly the controlled additions and behaviors associated with its underlying entanglement structure. It will also examine the security of the protocol, including extensions that enable encrypted teleportation. In addition, the talk will highlight developments related to quantum steering and Bell nonlocality, demonstrating how their interconnection with the protocol results in teleportation-based quantum steering and Bell-nonlocal certification. Furthermore, it will address the unification of teleportation with quantum error correction, leading to the concept of self-correcting teleportation. Finally, the talk will evaluate teleportation performance in noisy environments; specifically, it will compare the superiority of teleportation against direct quantum state transport, offering insights that could influence quantum repeater and network development by clarifying when teleportation is beneficial.

The formalism of quantum reference frames (QRFs) has gained more attention recently as a toolbox to deal with symmetries in quantum theories. Throughout the years, multiple approaches have surfaced, differing in how these symmetries are implemented and in their applicability. This poster talks about the relation between three of those: the perspective-neutral, the algebraic, and the effective semiclassical approach. The latter two are especially useful when implementing the constraint on the space of states proves to be a laborious task. The algebraic approach instead considers the state space of complex linear functionals on a kinematical algebra while the effective semiclassical one builds a quantum phase space parametrized by expectation values and fluctuations. We prove that for ideal QRFs, for which the frame orientations are orthogonal, these three approaches are equivalent. Moreover, we explore the QRF covariance of uncertainties and fluctuations and show that they are frame-dependent. Finally, we provide an outlook on building a quantum covariant effective phase space based on the effective one.

We propose an observer-dependent generalization of holography, by partially freezing different subregions in the spacetime. This gives an observer-dependent entanglement entropy formula as well as an observer-dependent holographic error correction code. We explain how the information are shared by different observers in this holography.

By analysing the high-resolution astronomical image data obtained from the next-generation optical and radio telescope arrays, astrophysics and cosmology is expected to advance dramatically. In this study, we extend shapelets—a method long used for analysing celestial morphologies, particularly those of galaxies (A. Refregier 2001; R. Massey and A. Refregier 2004)—using the Wigner function (E. Wigner 1932). We construct a group-theoretical framework for morphological evolution that incorporates information from propagation equations, such as radiative transfer. We discuss potential applications to the analysis of real data

We investigate the quantum field theory of a scalar field in a quantum superposition of gravitational potentials, where the causal structure of spacetime inevitably becomes state-dependent, allowing superpositions of space-like and time-like separations. Within a weak-gravity effective framework, we show that a consistent canonical description can be formulated without introducing new principles: equal-time canonical commutation relations remain fixed c-numbers, while microcausality necessarily becomes operator-valued and depends on the quantum state of the gravitational field. We illustrate this structure with an explicit 1+1-dimensional gravitational double-slit model and evaluate the gravitational decoherence.

We define entropic marginally outer trapped surfaces (E-MOTSs) as a generalization of apparent horizons. We then show that, under first-order perturbations around a stationary blackhole, the dynamical black hole entropy proposed by Hollands, Wald, and Zhang, defined on the background Killing horizon, can be expressed as the Wall entropy evaluated on an E-MOTS associated with it. Our result ensures that the Hollands--Wald--Zhang entropy reduces to the standard Wald entropy in each stationary regime of a dynamical black hole, thereby reinforcing the robustness of the dynamical entropy formulation.

Recently, a novel semiclassical gravity model proposed by Oppenheim et al. has attracted considerable attention as a consistent model for describing interactions between quantum systems and classical gravity. However, the properties of this model have not yet been fully understood. In this work, based on the Oppenheim et al. model, we investigate the geodesic deviation of quantum particles coupled to a classical gravitational field with stochastic fluctuations. We analytically derive the Langevin equations of the geodesic deviation and calculate the gravitational strain spectrum estimated from the deviation. We then show that the Oppenheim et al. model, which introduces white-type noise, may be ruled out by observational data from gravitational-wave interferometers. Furthermore, noting that the physical origin of the stochastic fluctuations in the Oppenheim et al. model is not clear, we construct the new model in which effective fluctuations arise in a quantized gravitational field interacting with environmental quantum fields. We perform a similar spectral analysis for this model and present a detailed comparison with the Oppenheim et al. model.

We can compute the entropy for extremal black holes in String theory and Supergravity theories using Sen’s entropy function formalism, which is a formalism for the near-horizon geometry. We work with rotating extremal black holes in dimensionally reduced (5D to 4D) Kaluza-Klein theory coupled to a nontrivial Gauss-Bonnet term in four dimensions. We then compute the corrected black hole entropy using the entropy function formalism. Moreover, we can show the presence of two branches (ergo-free branch and ergo branch) in this theory, corresponding to different limiting cases of the full solution parameters, and we compute the entropy of both these branches explicitly. Next, we address the issue of flat directions along with the necessity of removing them from our theory, which is consistent with string theory and moduli stabilization. These directions are lifted by the addition of the higher-derivative corrections, in our case the Gauss-Bonnet term, which in turn allows us to verify the speculations made in hep-th/0606244 and 0706.1874 on the removal of flat directions through higher-derivative terms.

When probing a complex quantum system, one may face the problem that there is no hand-crafted measurement protocol to extract quantities of interest. The field of variational quantum sensing tackles this problem by using quantum machine learning. More specifically, one lets a parameterized quantum circuit interact with the complex quantum system, and tunes the parameters such that the output measurement statistics gives the desired outputs. In my talk, I will present an extension of this approach to quantum field theory on curved spacetime. Here, the probes are modeled as Unruh-DeWitt detectors with tunable free Hamiltonian. Their interaction is mediated by the quantum field which also acts as the investigated complex quantum system. A physical regime is presented for which the quantum field induces a unitary globally entangling gate without acting as a source of noise. The resulting "hardware efficient ansatz" is universal for quantum computation.

In recent years, the Quantum Geometric Tensor (QGT), which represents the local geometric features of Hilbert space, has attracted significant attention. However, conventional definitions cannot be applied when the states do not belong to the Hilbert space. In this study, we construct quantum geometry for operator spaces and provide a new definition of the QGT that is applicable even when quantum states are outside the Hilbert space. Furthermore, using this newly defined QGT, we elucidate the geometric structure of quantum phase transitions associated with frame transformations.

The double sigma model provides a T-duality symmetric formulation of string theory, yielding Double Field Theory (DFT) in its low-energy limit. It is also called "double string" or, in more generalized contexts, "metastring". It is known that the model reduces to conventional string theory upon choosing a specific polarization of the doubled target space. In this poster, I investigate S-matrices of the double sigma model in comparison to ordinary strings and discuss their implications for the structure of quantum spacetime.

We study the application of the intertwiner operator method to non-Abelian Chern–Simons theory in three dimensions, with particular emphasis on the role of non-local operators. Building on the general construction of the intertwiner as a map between a “free” (or asymptotic) BRST charge and the full interacting BRST charge, we analyze Chern–Simons theory on foliated manifolds while preserving covariance on the Cauchy surface. As anticipated in the introductory discussion, the canonical quantization of Chern–Simons theory naturally leads to the appearance of non-local structures, due to the decomposition of the gauge field into longitudinal and transverse components and to the absence of local propagating degrees of freedom. We show that the triviality of the local BRST cohomology in topological field theories implies that physical states and operators must be realized in non-local sectors of the functional space. We compare the canonical and holomorphic quantization schemes, highlighting how the latter provides a more natural framework for the construction of the intertwiner and for the assignment of the filtration underlying the BRST charge. Within this framework, the intertwiner establishes an explicit correspondence between the two quantizations and clarifies the emergence of non-local BRST-invariant observables. As an application, we show how the path ordering of non-Abelian Wilson loops arises naturally from the structure of the intertwiner, providing a unified perspective on non-locality, quantization, and observables in Chern–Simons theory.

Many paradigms in physics and chemistry involve interacting classical and quantum variables, with notable examples including molecular dynamics and semi-classical black hole physics. However, much less is understood about the thermodynamics of these systems, including whether such semi-classical dynamics are generally compatible with the second law. In this work we describe how a basic first question in classical-quantum thermodynamics – is there dynamics that preserves the thermal state? – may be answered in the affirmative. This provides a method of constructing consistent semi-classical dynamics with a provable second law of thermodynamics, as well as a blueprint for how models of classical gravity may be constructed without excessive heating. The results are illustrated using two simple models: an analytically solvable model of a qubit coupled to an overdamped classical system, and an underdamped classical-quantum oscillator model.

Entanglement between accelerated detectors in curved spacetime provides a non-local probe of spacetime curvature. Such non-local observables have a covariant and geometric representation in terms of bitensors like Synge’s world function and van Vleck determinant, which can be computed exactly for maximally symmetric spacetime. I will demonstrate how entanglement exhibits a distinct dependence on curvature and acceleration in de Sitter, thereby separating detector kinematics from background curvature. I will also discuss the behavior of these bitensors near FLRW and Bianchi Type I singularities, including exact series expansions for the world function and the limiting behavior of the van Vleck determinant and related quantities, providing insights into the causal structure near singularities. Together, these results highlight bitensors as computable probes in strong-gravity and quantum regimes.

This poster introduces a discrete framework for holographic screens in which both bulk semiclassical geometry and boundary theory are modeled on simplicial complexes. The bulk is described by a finite Lorentzian simplicial complex with a metric-compatible discrete Hodge star, while a codimension-2 leaf of a holographic screen is equipped with a quantum field theory whose kinematical configuration space is the cochain complex of the leaf. Bulk extremal surfaces anchored to leaf subregions define an area-based geometric entropy functional, which is then used to constrain the von Neumann entropies of reduced states on the leaf. The resulting construction is employed to explore the structure of the holographic screen theory and how semiclassical geometry is encoded in entanglement in a discrete setting.

Time is a subtle concept in quantum mechanics: it is usually treated as an external parameter, and the existence of a self-adjoint time operator is constrained by Pauli’s theorem, although Aharonov and Bohm introduced a symmetric operator associated with the time of arrival. In recent years, Lee and Tsutsui have proposed a measurement-theoretic framework for uncertainty relations in which a quantum measurement induces a map from classical observables (real functions on the outcome space) to quantum observables (operators on the system Hilbert space). This map is called the Lee–Tsutsui adjoint, or pullback. We refer to this framework as the Lee–Tsutsui (LT) formalism. In parallel, a Gaussian wave-packet basis enables the construction of realistic finite-resolution measurement models. In this talk, we first review our previous results on position and momentum obtained by applying the LT formalism to a Gaussian wave-packet measurement model. We then present our recent result for time: by combining the LT formalism with a Gaussian wave-packet basis, we construct a time operator as a pullback operator and discuss its properties.

The Page-Wooters (PW) mechanism provides a relational notion of physical time evolution in setups with time reparametrization invariance. This gives a conceptual resolution to the "problem of time" in quantum gravity. There are many diffeomorphism-invariant notions of time evolution, relative to different choices of "clock" degrees of freedom. The aim of this talk is to implement one such intrinsic notion of time in the context of the AdS/CFT correspondence. Namely, we will be working in the setup of 1+1-dimensional Jackiw-Teitelboim (JT) gravity coupled to matter, whose holographic dual is well-understood. We consider a fixed boundary corner and its associated bulk causal diamond, which we foliate into constant-mean-curvature (CMC) slices. This foliation provides an intrinsic clock degree of freedom: the extrinsic curvature of the bulk spatial slice. We show how to obtain a physical time evolution of the matter and other geometric degrees of freedom relative to this clock. Crucially, this is not a gauge evolution, even though the boundary corner is held fixed. We then explain how to implement this physical flow in the dual boundary theory, via certain operator insertions at the corner. This provides an important new entry into the holographic dictionary, allowing one to access intrinsically-defined bulk time evolution from the boundary, further casting light on the emergence of spacetime from the dual theory.

The canonical quantization of general relativity is riddled with issues at the formal level, e.g., the problem of time, choice of ordering, observables, etc. We address these issues and investigate the imprints of ambiguities appearing in the quantization of a flat-Friedmann-Lemaître-Robertson-Walker model with reference fluid. The standard approach to incorporate the quantum gravity effects into the semiclassical analysis is to adopt an effective geometry from the QG model representing the quantum-corrected regular spacetime. Since the relevant observables are usually made out of conjugate variables that do not commute in QG, the expectation value of only one variable might not suffice. This ambiguity in the notion of effective geometry is studied for the case of a perfect fluid dominated universe. A generalized ordering scheme for the Hamiltonian is considered, and we study the implications of different ordering choices on the dynamics of the quantum Universe. We demonstrate that the imprints of the operator ordering ambiguity are minimal, and quantum fluctuations are small in the case of sharply peaked states, leading to a consistent notion of a quantum-corrected spacetime defined via the expectation value of the scale factor. Surprisingly, the ordering imprints survive far away from the singularity through the quantum fluctuations in the quantum-corrected spacetime for broadly peaked states.

Null foliations of asymptotically flat spacetimes are especially well suited for describing the physics at the conformal boundary, since null infinity is itself a null hypersurface. Using such a foliation, one can explicitly track how intrinsic geometric structures evolve and asymptote to null infinity. In this talk, we study null hypersurfaces approaching null infinity in conformally compactified spacetimes within the Bondi-Sachs gauge using Carrollian geometry. We show that the intrinsic dynamical equations on null hypersurfaces, namely Raychaudhuri and Damour equations, give rise to the Bondi mass-loss formula and the angular momentum equation. Additionally, we construct the null Brown-York tensor and analyze the gravitational phase space at finite distance, in order to find the associated asymptotic charges in the null infinity limit.

The hydrodynamic approximation has been proposed as a promising scenario for the emergence of spacetime in quantum gravity. A key piece of supporting evidence is the realization of Schrödinger symmetry—a typical emergent symmetry—in various minisuperspace models. However, previous studies have been largely limited to simple two-dimensional minisuperspace systems, such as FLRW cosmology or vacuum black holes. Therefore, exploring whether this symmetry persists in more complex systems offers a valuable test for the generality of this framework.
In this poster, based on the research with Yuki Yokokura (KEK) [arXiv:2512.13651v2 [gr-qc]], I will present results on static spherically symmetric minisuperspace coupled with matter fields. These systems are structurally richer than vacuum models, classically describing diverse physical phenomena such as charged black holes and naked singularities. We identify a three-dimensional Schrödinger symmetry in two specific cases: (i) a system containing an electromagnetic field with a cosmological constant, and (ii) one containing a massless scalar field. Notably, while the symmetry is realized under different choices of the lapse function for these two cases, we find that the vacuum Schwarzschild minisuperspace exhibits a two-dimensional Schrödinger symmetry under both lapse choices as distinct realizations. Our findings suggest that Schrödinger symmetry is a robust feature extending beyond simple vacuum models, thereby strengthening the correspondence between gravity and quantum hydrodynamics.

We study quantum decoherence of curvature perturbations at superhorizon scales caused by the gravitational nonlinearities. We show that cubic gravitational couplings, constrained by the spatial diffeomorphism invariance, lead to infrared (IR) and ultraviolet (UV) divergences in the decoherence rate at one loop. These divergences arise from fluctuations of deep IR modes which look like a background mode for a local observer and violent zero-point fluctuations in the deep UV, respectively. We argue that these divergences are unobservable, as they vanish when considering proper observables. We consider correlators defined using the geodesic distance for IR divergences and time-averaged correlators for UV divergences. To account for these observer's perspectives, we propose to consider an effective quantum state, defined in terms of actual observables, as a more appropriate probe of the quantum coherence of the system measured by an observer. We then evaluate the finite decoherence rate induced by superhorizon environment during inflation and at late universe. This talk is based on the paper arXiv:2504.10472.

We revisit boundary electromagnetic duality (tentative).

Whether gravity is quantum or not is one of the biggest unsolved problems in modern physics. To address this question experimentally, recent proposals such as the BMV experiment aim to test for gravity-mediated entanglement. However, gravity is an extremely weak interaction, and it takes a long time for measurable levels of quantum entanglement to be generated, during which decoherence tends to destroy it. Our research proposes a method to overcome these issues by using parametric resonance to rapidly amplify the generation of gravity-induced entanglement. We model a system of two gravitationally coupled oscillators and show that by operating in an instability region, entanglement can be generated exponentially, reaching a measurable level in a short time.

Quantum teleportation needs a pre-shared entanglement; that entanglement distribution needs a quantum channel connecting the sender and receiver. If the primary goal is quantum state transmission, why not send the state directly instead of using it for entanglement pre-distribution? While quantum teleportation is often considered superior, no work has explicitly shown that superiority. To explore this, we developed a toy model incorporating bit-flip, phase-flip, depolarizing, amplitude-damping, and phase-damping noise. We assumed that the decoherence rate parameters are linearly proportional to distance or time. We calculated the fidelity of the teleported state affected by these noises and compared it to that of direct state transmission, which serves as the benchmark for evaluating teleportation performance. Our results showed that teleportation performs better in distance-dependent scenarios, but not in time-dependent ones. In the latter, teleportation is superior at higher noise parameters but loses its superiority in the lower noise parameters. Lastly, we briefly discuss a physical system that may be compatible with the proposed noise toy model. The findings could influence quantum repeater and network development by clarifying when teleportation is beneficial.

Despite the empirical success of QED, its theoretical formulation remains unsatisfactory. The infrared problem remains one of the biggest conceptual puzzles, whose full resolution by all indication will teach us something new and profound about our world. In this work we reexamine carefully existing literature on this topic, putting into question the standard interpretation of asymptotic states as electrons surrounded by a cloud of soft photons. Furthermore, we employ the formalism of dynamical reference frames that allows us to dress the charged matter fields at a classical level. We can then quantize the system to study its dynamics perturbatively and compare with the results obtained by dressing at a quantum level.

One of the high-energy regimes explored in string theory is the near-horizon region of black holes. It is expected that Hawking radiation is emitted from this region, and stringy corrections to this Hawking radiation have been extensively studied. However, these corrections to the radiation spectrum have long been thought to be extremely small. Recently, a new perspective has been proposed: while corrections to the radiation spectrum indeed remain small, it has been argued that large corrections may arise in the time dependence of the radiation intensity. As a result, the intensity of Hawking radiation is expected to rapidly decay after the scrambling time, eventually leading to the termination of Hawking radiation. Since this prediction is based on string-inspired models, it remains necessary to derive it more directly from string theory itself. In this talk, we regard black hole formation and evaporation as string scattering processes and focus on the emission time of wave packets, that is time-delay, as means to support this prediction. Relation to the spacetime uncertainty principle will also be discussed.