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Hiroaki Matsueda

Publications and source records attributed to Hiroaki Matsueda.

At least 37 records · Page 2Linked to original sources
arXiv2023

Photoinduced pseudospin-wave emission from charge-density-wave domain wall with superconductivity

We study photoinduced dynamics triggered by an inhomogeneity due to competition between charge density waves (CDWs) and superconductivity. As a simple example, we consider the superconducting (SC) interface between two CDW domains with opposite signs. The real-time dynamics are calculated within the time-dependent Hartree--Fock--Bogoliubov framework, where the order parameter dynamics and the nonequilibrium quasiparticle distribution functions are studied. We also calculate the various dynamical response functions within a generalized random phase approximation. Through comparisons between the real time dynamics and the analysis of the response functions, it is found that the photo-driven SC interface can emit collective modes of the SC order parameter. This is analogous to the spin wave emission from the magnetic domain wall in an antiferromagnet, particularly in the case of a low driving frequency, where the order parameters can be mapped onto the pseudospin picture. In the high-frequency case, we find a domain wall melting caused by changes in the quasiparticle distribution, which induces superconductivity in the whole system.

cond-mat.supr-con↗
arXiv2022

Derivation of Interacting Two-Qubit Dynamics from Spin-Boson Model

We derive damping equations of motion for interacting two-spin states from a spin-boson model in order to examine qubit dynamics in quantum computers. On the basis of the composite operator method, we develop the Caldeira-Leggett approach for open quantum systems so that the entanglement dynamics originated from the two-spin correlation can be taken. We demonstrate numerical results for time dependence on the two-spin dynamics. We find that the relaxation of the total spin is described by a quantum version of the Landau-Lifshitz-Gilbert equation for magnetic materials. We also find that a two-spin composite mode keeps oscillation even after the total spin has been fully relaxed. We thus conclude that the two-spin correlation due to the presence of the composite mode is stable against dissipation. We consider the mechanism of why the correlation is maintained.

quant-ph↗
arXiv2022

Entanglement distillation toward minimal bond cut surface in tensor networks

In tensor networks, a geometric operation of pushing a bond cut surface toward a minimal surface corresponds to entanglement distillation. Cutting bonds defines a reduced transition matrix on the bond cut surface and the associated quantum state naturally emerges from it. We justify this picture quantitatively by evaluating the trace distance between the maximally entangled states and the states on bond cut surfaces in the multi-scale entanglement renormalization ansatz (MERA) and matrix product states in a canonical form. Our numerical result for the random MERA is in a reasonable agreement with our proposal. The result sheds new light on a deeper understanding of the Ryu-Takayanagi formula for entanglement entropy in holography and the emergence of geometry from the entanglement structure.

hep-th↗
arXiv2022

Excitonic Correlations, Spin-State Ordering, and Magnetic-Field Effects in One-Dimensional Two-Orbital Hubbard Model for Spin-Crossover Region

The electronic properties of excitonic insulators have been examined precisely in recent years. Pictures of exciton condensation may be applied to the spin-state transition observed in perovskite cobalt oxides. We examine the crystal-field and magnetic-field dependences of spatial spin structures on the basis of the density matrix renormalization group method using an effective model for the one-dimensional two-orbital Hubbard model in strong-coupling limit. We find an excitonic insulating (EI) phase and a spin-state ordering (SSO) phase in the intermediate region between low-spin and high-spin phases. In the EI phase, spin-triplet excitons are spatially fluctuating due to quantum effects, and an incommensurate spin correlation realizes. The analyses of a spin gap and degeneracy of entanglement spectra suggest the realization of the Haldane-like edge state in the EI phase. In the SSO phase, 3-fold or incommensurate SSO structures realize depending on the crystal-field splitting. These structures are stabilized as a result of the competition of exchange interactions between spin states.

cond-mat.str-el↗
arXiv2021

Two-step dynamics of photoinduced phonon entanglement generation between remote electron-phonon systems

The generation of quantum entanglement between phonons in photoirradiated remote electron-phonon systems is numerically studied. Upon excitation by a visible/ultraviolet laser pulse, the entanglement of electrons is immediately generated and that of phonons follows via electron-phonon interactions, i.e., the entanglement generation of phonons is a two-step process. Therefore, it is important to design the temporal properties of incident optical pulses in order to control the entanglement of electrons and/or phonons. These features are revealed by the quantum mutual information and the composite modes derived from the Heisenberg equation of motion. The calculated results also show that the dynamics of the phonon entanglement can be observed by time-resolved spectroscopy on the scattered light.

cond-mat.mes-hall↗
arXiv2021

Quantum Singular Value Decomposition of Spin Correlation Matrix in One-Dimensional Heisenberg Model

We present singular value decomposition of spin correlation matrix defined from the ground state of one-dimensional antiferromagnetic quantum Heisenberg model. The decomposition creates a data set that coincides with various domain excitations from classical antiferromagnetic state. We determine the scaling relation for the singular values as a function of the domain size. The singular values are closely related to the square of weights of the bases in the ground-state wavefunction. The nature of the singular value decomposition is to precisely estimate the appropriate bases and corresponding weights of the ground-state wavefunction.

quant-ph↗
arXiv2019

Image-processing the topological charge density in the CP(N-1) model

We study the topological charge density distribution using the two-dimensional $CP^{N-1}$ model. We numerically compute not only the topological susceptibility, which is a spatially global quantity to probe topological properties of the whole system, but also the topological charge correlator with finite momentum. We perform Fourier power spectrum analysis for the topological charge density for various values of the inverse temperature $β$. We propose to utilize the Fourier entropy as a convenient measure to characterize spatial distribution patterns and demonstrate that the Fourier entropy exhibits nontrivial temperature dependence. We also consider the snapshot entropy defined with the singular value decomposition, which also turns out to behave nonmonotonically with the temperature. We give a possible interpretation suggested from the strong-coupling analysis.

hep-lat↗
arXiv2019

Banados-Teitelboim-Zanelli Black Hole in the Information Geometry

We examine the Banados-Teitelboim-Zanelli (BTZ) black hole in terms of the information geometry and consider what kind of quantum information produces the black hole metric in close connection with the anti-de Sitter space/conformal field theory (AdS/CFT) correspondence. We find a Hessian potential that exactly produces both the BTZ metric and the entanglement entropy formula for CFT_{1+1} at a finite temperature. Taking a free-falling frame near the event horizon is a key procedure to derive these exact results. We also find an alternative Hessian potential that produces the same BTZ metric, which is found using the duality relation based on the Legendre transformation. We realize that the dual representation originates from the entanglement Hamiltonian on the CFT side. Our results suggest that the present information-geometrical approach is very powerful for understanding the mechanism of the holographic renormalization group such as the AdS/CFT correspondence.

hep-th↗
arXiv2016

Random Fractal Ansatz for the configurations of Two-Dimensional Critical Systems

Critical systems have always intrigued physicists and precipitated the development of new techniques. Recently, there has been renewed interest in the information contained in their classical configurations, whose computation do not require full knowledge of the wavefunction. Inspired by holographic duality, we investigated the entanglement properties of the classical configurations (snapshots) of the Potts model by introducing an ansatz ensemble of random fractal images. By virtue of the central limit theorem, our ansatz accurately reproduces the entanglement spectra of actual Potts snapshots without any fine-tuning of parameters or artificial restrictions on ensemble choice. It provides a microscopic interpretation of the results of previous studies, which established a relation between the scaling behavior of snapshot entropy and the critical exponent. More importantly, it elucidates the role of ensemble disorder in restoring conformal invariance, an aspect previously ignored. Away from criticality, the breakdown of scale invariance leads to a renormalization of the parameter $Σ$ in the random fractal ansatz, whose variation can be used as an alternative determination of the critical exponent. We conclude by providing a recipe for the explicit construction of fractal unit cells consistent with a given scaling exponent.

cond-mat.stat-mech↗
arXiv2016

Inverse Mellin Transformation of Continuous Singular Value Decomposition: A Route to Holographic Renormalization

We examine holographic renormalization by the singular value decomposition (SVD) of matrix data generated by the Monte Carlo snapshot of the 2D classical Ising model at criticality. To take the continuous limit of the SVD enables us to find the mathematical form of each SVD component by the inverse Mellin transformation as well as the power-law behavior of the SVD spectrum. We find that each SVD component is characterized by the two-point spin correlator with a finite correlation length. Then, the continuous limit of the decomposition index in the SVD corresponds to the inverse of the correlation length. These features strongly suggest that the SVD contains mathematical structure the same as the holographic renormalization.

cond-mat.stat-mech↗
arXiv2016

Singular-Value-Decomposition Analysis of Associative Memory in a Neural Network

We evaluate performance of associative memory in a neural network by based on the singular value decomposition (SVD) of image data stored in the network. We consider the situation in which the original image and its highly coarse-grained one by SVD are stored in the network and the intermediate one is taken as an input. We find that the performance is characterized by the snapshot-entropy scaling inherent in the SVD: the network retrieves the original image when the entropy of the input image is larger than the critical value determined from the scaling. The result indicates efficiency of the SVD as a criterion of the performance and also indicates universality of the scaling for realistic problems beyond theoretical physics.

cond-mat.stat-mech↗
arXiv2016

Analytic Optimization of a MERA network and its Relevance to Quantum Integrability and Wavelet

I present an example of how to analytically optimize a multiscale entanglement renormalization ansatz for a finite antiferromagnetic Heisenberg chain. For this purpose, a quantum-circuit representation is taken into account, and we construct the exactly entangled ground state so that a trivial IR state is modified sequentially by operating separated entangler layers (monodromy operators) at each scale. The circuit representation allows us to make a simple understanding of close relationship between the entanglement renormalization and quantum integrability. We find that the entangler should match with the $R$-matrix, not a simple unitary, and also find that the optimization leads to the mapping between the Bethe roots and the Daubechies wavelet coefficients.

math-ph↗
arXiv2015

Hessian potential for Fefferman-Graham metric

The Fefferman-Graham metric is frequently used for derivation of the first law of the entanglement thermodynamics. On ther other hand, the entanglement thermodynamics is well formulated by the Hessian geometry. The aim of this work is to relate them with each other by finding the corresponding Hessian potential. We find that the deformation of the bulk Hessian potential for the pure AdS spacetime behaves as a source potential of the boundary Fisher metric, and the deformation coincides with the Fefferman-Graham metric. A peculiar feature different from related works is that we need not to use the Ryu-Takayanagi formula for the above derivation. The canonical parameter space in the Hessian geometry is a kind of the model parameter space, rather than the real classical spacetime in the usual setup of the AdS/CFT correspondence. However, the underlying mathematical structure is the same as that of the AdS/CFT correspondence. This suggests the presence of more global class of holographic transformation.

hep-th↗
arXiv2015

Correspondence between causality in flat Minkowski spacetime and entanglement in thermofield-double state: Hessian-geometrical study

We examine the Hessian potential that derives the flat Minkowski spacetime in $(1+1)$-dimension. The entanglement thermodynamics by the Hessian geometry enables us to obtain the entanglement entropy of a corresponding quantum state by means of holography. We find that the positivity of the entropy leads to the presence of past and future causal cones in the Minkowski spacetime. We also find that the quantum state is equivalent to the thermofield-double state, and then the entropy is proportional to the temperature. The proportionality is consistent with previous holographic works. The present Hessian geometrical approach captures that the causality in the classical side is converted into quantum entanglement inherent in the thermofield dynamics.

hep-th↗
arXiv2015

Hessian geometry and entanglement thermodynamics

We reconstruct entanglement thermodynamics by means of Hessian geometry, since this method exactly generalizes thermodynamics into much wider exponential family cases including quantum entanglement. Starting with the correct first law of entanglement thermodynamics, we derive that a proper choice of the Hessian potential leads to both of the entanglement entropy scaling for quantum critical systems and hyperbolic metric (or AdS space with imaginary time). We also derive geometric representation of the entanglement entropy in which the entropy is described as integration of local conserved current of information flowing across an entangling surface. We find that the entangling surface is equivalent to the domain boundary of the Hessian potential. This feature originates in a special property of critical systems in which we can identify the entanglement entropy with the Hessian potential after the second derivative by the canonical parameters, and this identification guarantees violation of extensive nature of the entropy.

hep-th↗
arXiv2015

Geometry and Dynamics of Emergent Spacetime from Entanglement Spectrum

We examine geometry and dynamics of classical spacetime derived from entanglement spectrum. The spacetime is a kind of canonical parameter space defined by the Fisher information metric. As a concrete example, we focus on the spectrum for free fermions in spatially one dimension. The spectrum has exponential family form like thermal probability distribution owing to mixed-state feature emerging from truncation of environmental degrees of freedom. In this case, the Fisher metric is given by the second derivative of the Hessian potential that can be identified with the entanglement entropy. We emphasize that the canonical parameters are nontrivial functions of partial system size by the truncation, filling fraction of fermions, and time. Then, the precise determination of this nontrivial mapping is necessary to derive the functional form of the Hessian potential that leads to correct entanglement entropy scaling. By this potential, we find that the emergent geometry becomes anti-de Sitter spacetime with imaginary time, and a radial axis as well as spacetime coordinates appears spontaneously. We also find that the information of the UV limit of the original free fermions lives in the boundary of the anti-de Sitter spacetime. These findings strongly suggest that the Hessian potential for free fermions has enough geometrical meaning associated with gauge-gravity correspondence. Furthermore, some deformation of the spectrum near the conformal fixed point is mapped onto spacetime dynamics. The fluctuation of the entanglement entropy embedded into the spacetime behaves like free scaler field, and the dynamics is described by the Einstein equation with a negative cosmological constant. Therefore, the Einstein equation can be regarded as the equation of original quantum state.

hep-th↗
arXiv2015

Photo-Induced Phase Transition in Charge Order Systems --Charge Frustration and Interplay with Lattice--

Lattice effects on photo-excited states in interacting charge frustrated system are examined. Real time dynamics in the interacting spinless fermion model on a triangular lattice coupled to lattice vibration are analyzed by applying the exact diagonalization method combined with the classical equation of motion. A photo-induced phase transition from the horizontal stripe-type charge order (CO) to the 3-fold CO occurs through a characteristic intermediate time domain. By analyzing the time evolution in detail, we find that this characteristic dynamics are seen when the electron and lattice sectors are not complementary to each other but show cooperative time evolutions. We also find that there are threshold values in the optical fluorescence and electron-lattice coupling for emergence of the photo-induced 3-fold CO. The dynamics are distinct from those from the vertical stripe-type CO, in which a monotonic CO melting occurs. A scenario of the photo-induced CO phase transition with lattice degree of freedom is presented from a view point of charge frustration.

cond-mat.str-el↗