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Recent Progress in Many-Body Theories (RPMBT22)

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Kasuga Auditorium (Kasuga Campus, University of Tsukuba)

Kasuga Auditorium

Kasuga Campus, University of Tsukuba

Tsukuba, Ibaraki, 305-8550, Japan
Description

22nd International Conference on Recent Progress in Many-Body Theories (RPMBT22) will be held in Tsukuba, Japan, September 23-27, 2024 (The reception and the registration are available on September 22). A series of the conferences offer an ideal opportunity to recognize important achievements and to showcase significant new results in various aspects of many-body physics.

The conference is hosted by Center for Computational Sciences, University of Tsukuba.

      

Conference program (PDF)

Local organizing committee

  • Ryotaro Arita (Univ. of Tokyo, Japan)
  • Yasuhiro Hatsugai (Univ. of Tsukuba, Japan)
  • Nobuo Hinohara (Univ. of Tsukuba, Japan)
  • Atsushi Hosaka (Osaka Univ., Japan)
  • Masaaki Kimura (RIKEN Nishina Center, Japan)
  • Takashi Nakatsukasa (Univ. of Tsukuba, Japan)
  • Shunsuke Sato (Univ. of Tsukuba, Japan)
  • Seiji Yunoki (RIKEN, Japan)

Acknowlegements

This event is supported by

     

Circulars & Programs
Maps
Misc
Photo
Participants
  • Adrian Del Maestro
  • Akitada Sakurai
  • Alessandro Roggero
  • Alexander Lichtenstein
  • Alexei Tsvelik
  • Anil Kumar
  • Aoi Hayashi
  • Armen Sedrakian
  • Arup Chakraborty
  • Atsushi Hosaka
  • Atsuya Kanai
  • Azar Tafrihi
  • Bhanu Das
  • Carlo Barbieri
  • Chengpeng Yu
  • Chisato Ruike
  • David Neilson
  • Davide Emilio Galli
  • Eckhard Krotscheck
  • EDUARDO FRADKIN
  • Erik Sorensen
  • Garnet Chan
  • Gerardo Ortiz
  • Han Xu
  • Hang Yu
  • Heidi Reinholz
  • Hidetoshi Nishimori
  • Hitoshi Nakada
  • Jane Kim
  • Jin Inoue
  • Jonas Flaten
  • Jong Han
  • Jordi Boronat
  • Kae Nemoto
  • Kaoru SEKIYA
  • Kazuhiro Yabana
  • Kenta Akai
  • Kenta Hagihara
  • Kenta Yoshimura
  • Kento Kitanaka
  • Khandker Quader
  • Kota Yoshinaga
  • Kotaro Uzawa
  • Kouhei Washiyama
  • LE THE ANH
  • Lukas Broers
  • Markus Holzmann
  • Masaaki KIMURA
  • Masatoshi Takano
  • Matteo Calandra
  • Matthew Foulkes
  • Minori Abe
  • Mrinal Kanti Giri
  • Nanako Shitara
  • Neill Lambert
  • Nobuo Hinohara
  • Noritaka Shimizu
  • Oskar Leinonen
  • Pierbiagio Pieri
  • Qiang ZHAO
  • Raymond BISHOP
  • Raúl Bombín Escudero
  • Riccardo Rossi
  • Rikio Konno
  • Ryo Watanabe
  • Ryoji Okamoto
  • Ryotaro Arita
  • Sara Conti
  • Seiji Yunoki
  • Shane Dooley
  • Shinichiro Akiyama
  • Shinsho Oryu
  • Shunsuke Sato
  • SIU A. CHIN
  • Sota Yoshida
  • Stefano Giorgini
  • Taishi Ochi
  • Taisuke Boku
  • Taisuke Hasegawa
  • Takashi Nakatsukasa
  • Takayuki Miyagi
  • Takumi Shoji
  • Tomoya Naito
  • Toshiya Osuka
  • Vittorio Soma
  • Xilin Zhang
  • Yasuhiro Hatsugai
  • Yoshihide Sato
  • Yukiya Chiba
  • Yuta Murakami
Contact
  • Sunday, 22 September
    • 18:00 → 20:00
      Registration & Welcome drink Cafe "Engi" (Cafe "Engi")

      Cafe "Engi"

      Cafe "Engi"

      Tsukuba Center Bldg. 1F, Tsukuba 30500031

      See "Useful information"

  • Monday, 23 September
    • 09:00 → 09:50
      Registration Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
    • 09:50 → 11:00
      Session: Opening (Chair: NAKATSUKASA, Takashi) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 09:50
        Welcome by Director of CCS 5m
        Speaker: Taisuke Boku (University of Tsukuba)
      • 09:55
        Welcome by IAC chair 5m
        Speaker: Gerardo Ortiz (Indiana University and Institue for Advanced Study, Princeton)
        RPMBT-Intro-Ortiz.key
      • 10:00
        Simulating dissipative quantum many-body dynamics via the time-dependent Variational Monte Carlo method 30m

        The rapid advancement in quantum technologies has heightened interest in surpassing classical simulators through quantum supremacy. A significant challenge in this endeavor is the effective understanding and manipulation of open quantum systems, which are crucial for the progression of advanced quantum technologies. While several approximate methods have been proposed to simulate the dynamics of open quantum systems, their applicability has largely been confined to small-scale systems [1].
        In this study, we introduce a novel approach utilizing the time-dependent Variational Monte Carlo (tVMC) method. Our method employs the unravelling of master equations to produce a series of quantum trajectories governed by a stochastic Schrödinger equation (SSE). When the effect of the environment can be well approximated by a Markovian master equation, by solving multiple independent trajectories we reconstruct time-dependent observables consistently.
        We apply this method to dissipative quantum many-body models, exploring various variational ansätze, ranging from Jastrow wavefunctions to more advanced Neural Networks Quantum States (NNQS) [2, 3].

        References
        [1] H. Weimer, A. Kshetrimayum and R. Orús, Rev. Mod. Phys. 93, 015008 (2021).
        [2] G. Carleo and M. Troyer, Science 355, 602 (2017).
        [3] M. J. Hartmann and G. Carleo, Phys. Rev. Lett. 122, 250502 (2019).

        Speaker: Prof. Davide Emilio Galli (Dipartimento di Fisica, Università degli Studi di Milano)
        DavideEmilioGalli.pdf
      • 10:30
        A fully-programmable universal quantum simulator using Floquet technology 30m

        With the size of quantum information processors increasing, quantum simulation has become one of its promising near-future applications. Now it is known that when the computational problem at hand is difficult, the difficulty often appears in terms of an increased quantum circuit depth in gate based implementations or as many-body interaction terms in Hamiltonian based computation. In particular, many-body interactions are difficult to directly implement. To circumvent such difficulties, we introduce a reverse engineering based Floquet technology to turn one-dimentional non-universal superconducting qubit arrays Into a full-programmable universal quantum simulator. A time dependent Hamitonian can give a unitary map equivalent of the time-evoluation of a non-trivial Hamiltonian different from the original physical Hamiltonian. Using this Floquet nature, we can tune the evolution time of this physical resource to create an arbitrary Hamiltonian. This creates a tradeoff between the time necessary for the simulation and the simplicity of its hardware implementation. We discuss the advantages and disadvantages of the universal quantum simulator as a model to investigate complex quantum dynamics as well as for experimental implementation.

        Speaker: Prof. Kae Nemoto (Okinawa Institute of Science and Technology)
    • 11:00 → 11:30
      Coffee break 30m Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
    • 11:30 → 12:25
      Session: Quantum information and computing (Chair: ORTIZ, Gerardo) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 11:30
        Quantum Computing for Nuclear Physics 30m

        With the recent experimental realization of quantum computing devices containing tens to hundreds of qubits and fully controllable operations, the theoretical effort in designing efficient quantum algorithms for a variety of problems has seen a tremendous growth worldwide. In this talk I will discuss the potential impact of quantum computing for application in nuclear physics and present some recent results of quantum simulations for simple nuclear models on current generation devices.

        Speaker: Alessandro Roggero (University of Trento, TIFPA)
        roggero.pdf
      • 12:00
        Simple many-body dynamics is a powerful quantum reservoir 25m

        Many body quantum systems internally have exponentially huge Hilbert spaces and complex dynamics. Much research has been done to find ways to exploit this complexity for practical applications and information processing. Quantum reservoir computing has garnered attention as an approach to directly utilize the complexity of quantum dynamics as a computational resource[1,2]. It is considered for potential applications with Noise-Intermediate Scale Quantum (NISQ) devices. Several studies have reported that complex dynamics possess enough complexity to serve as effective reservoirs. On the contrary, can simple quantum systems be used as reservoirs? For example, can quantum systems, which classical computers can efficiently simulate, work well as reservoirs? This talk will discuss how simple a system can be used as a quantum reservoir and where it cannot be. Furthermore, we discuss the boundary between potent and poor reservoirs[3].
        [1] Fujii, Keisuke, et al. "Harnessing disordered-ensemble quantum dynamics for machine learning." Phys. Rev. Applied 8 024030 (2017).
        [2] A. Sakurai et al., “Quantum Extreme Reservoir Computation Utilizing Scale-Free Networks,” Phys. Rev. Applied 17, 064044 (2022).
        [3] Sakurai, Akitada, et al. "Simple Hamiltonian dynamics is a powerful quantum processing resource." arXiv preprint arXiv:2405.14245 (2024).

        Speaker: Akitada Sakurai (OIST)
        2024.09.23.RPMBT22.pdf
    • 14:00 → 15:20
      Session: Computational many-body physics (Chair: NEILSON, David) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 14:00
        Approximating Many-Electron Wave Functions using Neural Networks 30m

        Exact wave functions of molecules and solid-state simulation cells containing more than a few electrons are out of reach because they are NP-hard to compute in general, but approximations can be found using polynomially scaling algorithms. A key challenge in many such approaches is the choice of an approximate parameterized wave function, which must trade accuracy for efficiency. Neural networks have shown impressive power as practical function approximators and promise as a way of representing wave functions for spin systems, but electronic wave functions have to obey Fermi-Dirac statistics. This talk describes a deep learning architecture, the Fermionic neural network, which is capable of approximating many-electron wave functions and greatly outperforms conventional approximations. Applications to a range of problems in molecular chemistry and solid-state physics will be discussed.

        Speaker: Prof. Matthew Foulkes (Imperial College London)
        talk_Tsukuba_Foulkes.pdf
      • 14:30
        Exact Field Induced Ground States of the Quantum Compass Model 25m

        We consider the square lattice S=½ quantum compass model (QCM) parameterized by
        Jx, Jz, under an in-plane field. At the special field value, (hx,hz)=2S(Jx,Jz), we show that the QCM Hamiltonian may be written in a form such that two simple product states can be identified as exact ground-states, below a gap. Exact excited states can also be found. The exact product states are characterized by a staggered vector chirality, attaining a non-zero value in the surrounding phase, and can also be realized in 1D spin chains. The resulting gapped phase occupies most of the in-plane field phase diagram, but is clearly distinct from the high field polarized phase. Using iDMRG and iPEPS techniques in combination with exact diagonalizations and analytical arguments, we determine the complete in-plane field phase diagram [1]. Our findings are important for understanding the field dependent phase diagram of materials with predominantly directionally-dependent Ising interactions, and duality relations connects the QCM model to the Xu-Moore model and the toric code.

        Speaker: Erik Sorensen (McMaster University)
        RPBMTSep2024.pdf
      • 14:55
        Spin-S Kitaev-Heisenberg model on the honeycomb lattice: A high-order treatment of its phase diagram via the coupled cluster method 25m

        Abstract (PDF)

        Speaker: Raymond BISHOP (University of Manchester, UK)
        abstract.pdf Raymond_BISHOP.pdf
    • 15:20 → 15:50
      Coffee break 30m Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
    • 15:50 → 17:15
      Session: Quantum fluids and ultracold gases (Chair: GALLI, Davide Emilio) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 15:50
        Neural-network quantum states for ultra-cold Fermi gases 30m

        Ultra-cold Fermi gases exhibit a rich array of quantum mechanical properties, including the transition from a fermionic superfluid Bardeen-Cooper-Schrieffer (BCS) state to a bosonic superfluid Bose-Einstein condensate (BEC). While these properties can be precisely probed experimentally, accurately describing them poses significant theoretical challenges due to strong pairing correlations and the non-perturbative nature of particle interactions. In this talk, I will introduce our recent development­­—a Pfaffian-Jastrow neural-network quantum state featuring a message-passing architecture, designed to efficiently capture pairing and backflow correlations. We benchmark our approach on existing Slater-Jastrow frameworks and state-of-the-art diffusion Monte Carlo methods, demonstrating a performance advantage and the scalability of our scheme. We show that transfer learning stabilizes the training process in the presence of strong, short-ranged interactions, and allows for an effective exploration of the BCS-BEC crossover region. Our findings highlight the potential of neural-network quantum states as a promising strategy for investigating ultra-cold Fermi gases. Finally, I will discuss initial results applying this ansatz to nuclear matter and nuclei.

        Speaker: Dr Jane Kim (Ohio University)
        RPMBT22.pdf
      • 16:20
        From ground state energies towards excitations for extended quantum systems 30m

        Iterated backflow and neural network wave functions indicate a systematic way to improve the accuracy of quantum Monte Carlo (QMC) calculations of ground state energies of large (but finite) quantum systems in two or three spatial dimensions at zero temperature. I will illustrate recent improvements on the calculations of the ground state phase diagram of the electron gas and of the phase transition from liquid to solid helium. Then I will discuss the difficulties one faces when extending QMC calculations to study excitation properties of bulk materials, e.g. electronic band gaps in solid hydrogen and the effective mass of the electron gas.

        Speaker: Markus Holzmann (LPMMC, CNRS & UGA Grenoble)
        talk.pdf
      • 16:50
        Boson-fermion pairing in resonant Bose-Fermi mixtures 25m

        Abstract (PDF)

        Speaker: Pierbiagio Pieri (University of Bologna & Istituto Nazionale di Fisica Nucleare)
        abstract.pdf Pieri-Tsukuba.pdf
  • Tuesday, 24 September
    • 09:00 → 10:25
      Session: Computational many-body physics (Chair: MIYAGI, Takayuki) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 09:00
        How to describe all nuclei at polynomial cost in the ab initio framework 30m

        A strong effort will be dedicated in the coming years to extend the reach of ab initio nuclear-structure calculations to heavy doubly open-shell nuclei. In order to do so, the most efficient strategies to incorporate dominant many-body correlations at play in such nuclei must be identified. With this motivation in mind, the present work pedagogically analyses the inclusion of many-body correlations and their impact on binding energies of Calcium and Chromium isotopes. Employing an empirically-optimal Hamiltonian built from chiral effective field theory, binding energies along both isotopic chains are studied via a hierarchy of approximations based on polynomially-scaling expansion many-body methods. The spherical mean-field approximation is shown to display specific shortcomings in Ca isotopes that are efficiently corrected via the consistent addition of low-order dynamical correlations on top of it. While the same setting cannot appropriately reproduce binding energies in doubly open-shell Cr isotopes, allowing the unperturbed mean-field state to break rotational symmetry permits to efficiently capture the static correlations responsible for the phenomenological differences observed between the two isotopic chains. Eventually, the present work demonstrates in a pedagogical way that polynomially-scaling expansion methods based on unperturbed states that possibly break (and restore) symmetries constitute an optimal route to extend ab initio calculations to heavy closed- and open-shell nuclei.

        Speaker: Dr Vittorio Somà (CEA Saclay)
        RPMBT22_Soma.pdf
      • 09:30
        Surrogate models for quantum many-body systems 30m

        Quantum many-body systems, particularly in nuclear physics, present significant computational challenges due to their complex interactions and high-dimensional state spaces. Surrogate models offer a promising solution by providing simplified yet accurate representations of these systems, reducing computational costs and enhancing scalability.

        This talk will focus on the development and application of surrogate models specifically for nuclear many-body problems. We will explore various approaches, including machine learning techniques and reduced basis method.

        Speaker: Sota Yoshida (Utsunomiya University)
        RPMBT22_SYoshida.pdf
      • 10:00
        A Comparison of Methods for Simulating Quantum Dot Dynamics 25m

        Within the field of computational quantum many-body dynamics, several approaches exist to approximating and simulating the time evolution of quantum systems with multiple particles. In this presentation, four numerical methods will be compared: the time-dependent configuration-interaction (TDCI) method, the multi-configurational time-dependent Hartree-Fock (MCTDHF) method, the time-dependent coupled-cluster (TDCC) method and time-dependent density functional theory (TDDFT). Strengths and weaknesses of these methods will be discussed, as well as possibly beneficial ways to combine them, with respect to simulation of spatially confined systems relevant to quantum chemistry, nuclear physics and quantum computing.

        The TDCI, MCTDHF and TDCC methods all rely on a basis of single-particle states which has large impact on the size of the computations involved. The choice of a good basis is therefore also of relevance when discussing these methods, and in this presentation an overview of some alternatives with analytic, geometric or physical benefits will be discussed, as well as the possibility of using DFT to find a good one-body basis which sufficiently spans the many-body dynamics of a given system.

        The presentation is partly based on an upcoming paper by Morten Hjorth-Jensen, Oskar Leinonen, Jonas B. Flaten and others from the University of Oslo, discussing technical aspects of and comparing various methods for simulating quantum dot systems, with simulations of several particles in a 3D harmonic oscillator as an example.

        Speaker: Jonas Flaten (University of Oslo)
        Jonas Flaten.pdf
    • 10:25 → 10:55
      Coffee break 30m Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
    • 10:55 → 12:20
      Session: Condensed matter physics (Chair: HATSUGAI, Yasuhiro) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 10:55
        Theoretical Modeling of Ultrafast Phase Transitions from the Femtosecond to the Picosecond Scale 30m

        In this talk, I will introduce a theoretical approach to ultrafast phase transitions able to capture both the electron and phonon dynamics after laser pumping on a time scale ranging from a few femtoseconds to several picoseconds after laser irradiation.

        At short times, the method relies on the solution of the Bloch equations coupled to the Ehrenfest dynamics. It includes the electric field of the pump as well as the electron-phonon, electron-electron, and phonon-phonon scattering completely from first principles.

        At longer times before recombination, when the electron-electron interaction generates a photoexcited quasi-equilibrium electron-hole plasma, the approach is based on a constrained density functional perturbation theory (cDFPT) scheme accounting both for the presence of holes in the valence band and electrons in the conduction band (two Fermi levels approach). In this framework, calculation of forces, phonon dispersion, and electron-phonon coupling are possible, as well as molecular dynamics with machine learning potential in the presence of an electron-hole plasma.

        I will showcase the application of the method to several materials ranging from low-dimensional dichalcogenides to ferroelectrics and thermoelectrics.

        This work is funded by the European Union (ERC, DELIGHT, 101052708)

        Speaker: Prof. Matteo Calandra (University of Trento)
        Talk_Calandra_Tsukuba.pdf
      • 11:25
        Ab initio structural optimization at finite temperatures based on anharmonic phonon theory 30m

        In this presentation, I will report on the development of first-principles structural optimization at finite temperatures and their applications. At zero temperature, structural optimization commonly involves minimizing the energy of the system based on density functional theory. However, it is necessary to consider minimizing the free energy at finite temperatures. In doing so, it is essential to consider the contributions of phonons, including anharmonic terms. We have formulated a method based on anharmonic phonon theory. In particular, we developed a technique for efficiently evaluating the interatomic force constant, which we applied to BaTiO3 and LiBO3 (B=Ta, W, Re, Os). Our method has been found to accurately evaluate the experimental transition temperatures of structural phase transitions in both insulators and metals.

        [1]R. Masuki, T. Nomoto, R, Arita, and T. Tadano, Phys. Rev. B 106. 224104 (2022)
        [2]R. Masuki, T. Nomoto, R, Arita, and T. Tadano, Phys. Rev. B 110, 094102 (2024)

        Speaker: Prof. Arita Ryotaro (Department of Physics, University of Tokyo)
        test.pdf
      • 11:55
        Understanding correlated d- and f-electron systems using DFT and eDMFT methods 25m

        Abstract (PDF)

        Use Own PC

        Speaker: Prof. Khandker Quader (Department of Physics, Kent State University, Kent, OH, USA)
        abstract.pdf
    • 14:00 → 15:20
      Session: New frontiers (Chair: DAS, Bhanu) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 14:00
        Pseudomodes: from solving the spin-boson model to finding ground states 30m

        Pseudomodes have grown in popularity in recent years as an intuitive numerical method for solving the general problem of a quantum system coupled to a Gaussian environment. I will summarize the various formulations of pseudomodes that have appeared in the literature, and demonstrate how they can be used to model non-Markovian bosonic environments and the Kondo effect in the single-impurity Anderson model. I will finish with showing how they can be used an convenient protocol for performing quantum simulation of open quantum systems and, consequently, for acting as engineered environments for dissipative state engineering.

        Speaker: Neill Lambert (RIKEN)
        rpmbt_v1.pdf
      • 14:30
        Recent advances in understanding the sign problem in path integral Monte Carlo simulation of harmonic fermions 25m

        Abstract (PDF)

        Speaker: Prof. SIU CHIN (Texas A&M University)
        abstract.pdf SiuChin.pdf
      • 14:55
        Decoherence of a qubit interacting with a complex spin bath 25m

        Abstract (PDF)

        Speaker: Nanako Shitara (Department of Physics, University of Colorado Boulder, Colorado 80309, USA)
        abstract.pdf NanakoShitara.pdf
    • 15:20 → 15:50
      Coffee break 30m Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
    • 15:50 → 17:10
      Session: Nuclear physics (Chair: KIMURA, Masaaki) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 15:50
        Recent advances in ab initio calculations of heavy nuclei 30m

        One of the fundamental problems in nuclear physics is to predict the properties of nuclei based on underlying nuclear interactions. The applicability of nuclear ab initio calculation has been expanding in the past few decades, and systematic calculations can be performed up to mass number $\sim$ 100. However, the applications for heavier systems are limited primarily due to the memory-expensive three-nucleon (3N) interaction matrix elements. Modern nuclear ab initio calculations begin with the nucleon-nucleon (NN) and 3N interactions, benefitting from chiral effective field theory. For medium- and heavy-mass nuclei, one can apply basis expansion methods such as the coupled-cluster method, self-consistent Green's function method, many-body perturbation theory, and in-medium similarity renormalization group, starting from the NN and 3N matrix elements expressed with the spherical harmonic-oscillator (HO) basis set, where a typical calculation is performed within 13 or 15 major-shell space. The memory requirement of the 3N matrix elements in such space will exceed 10 TB, and one needs another truncation for 3N matrix elements, known as $E_{\rm 3max}$ defined by the sum of 3N HO quanta. It turned out that the current $E_{\rm 3max}$ limit does not allow us to obtain converged results for nuclei heavier than $A~\sim$ 100. To overcome the limitation, we proposed a new storage scheme for the 3N matrix elements, where we exploit the feature of the normal-ordered two-body approximation widely used in the basis expansion methods. This new scheme enables us to compute the known heaviest doubly magic nucleus $^{208}$Pb. In this presentation, I will show recent ab initio results for some heavy mass nuclei, including a prediction for the neutron-skin thickness of $^{208}$Pb.

        Speaker: Takayuki Miyagi (University of Tsukuba)
        RPMBT22_miyagi.pdf
      • 16:20
        BCS-BEC crossover in nuclear matter and related systems 25m

        I will discuss the features of BCS-BEC crossover in nuclear systems and by extension also in fermionic ultra-cold gases in the presence of population imbalance. The phase diagram of such systems will be discussed including phases with broken space symmetries and phase separation. It will be pointed out that several tri-critical points appear on the phase diagram of such a system.

        Speaker: Prof. Armen Sedrakian (FIAS and Uni. of Wroclaw)
        RPMBT2024.pdf
      • 16:45
        Self-consistent single-nucleon potential describing nuclear structure to intermediate-energy scattering 25m

        Abstract (PDF)

        Speaker: Hitoshi Nakada (Chiba University)
        abstract.pdf Hitoshi_Nakada.pdf
    • 17:10 → 17:30
      Session: Poster indexing (Chair: KIMURA, Masaaki) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 17:10
        [Indexing] Self-consistent renormalization theory of anisotropic spin fluctuations in nearly ferromagnetic metals 1m

        Abstract (PDF)

        Speaker: Prof. Rikio Konno (Kindai University Technical College )
        RPMBT22_konno.pdf
      • 17:12
        [Indexing] Variational method with an explicit energy functional for symmetric nuclear matter taking into account the spin-orbit force 1m

        Abstract (PDF)

        Speaker: Toshiya Osuka (Department of Physics and Applied Physics, Waseda University)
        indexing_Osuka.pdf
      • 17:13
        [Indexing] Variational method with an explicit energy functional for neutron matter at finite temperature taking into account the spin-orbit force 1m

        Abstract (PDF)

        Speaker: Kento Kitanaka (Department of Physics and Applied Physics, Waseda Univesity)
        poster_presentation.pdf
      • 17:14
        [Indexing] Shape fluctuation in low-lying states in $N \approx 40$ neutron-rich nuclei 1m

        Abstract (PDF)

        Speaker: Kouhei Washiyama (University of Tsukuba)
        washiyama-poster-indexing.pdf
      • 17:15
        [Indexing] Nuclear structure study using a hybrid approach of shell model and Gogny-type density functionals 1m

        The Gogny-type density functionals have finite-range and density-dependent terms. The parameters of the functionals are designed not only to reproduce the basic properties of finite nuclei but also to satisfy the saturation properties of nuclear matter. Consequently, calculations using a single density functionals can describe experimental data in various mass regions. However, the mean-field calculations using the functionals miss some corrections. In contrast, there are semi-empirical methods that construct a shell-model Hamiltonian by fitting experimental values. The shell-model (configuration interaction) calculations can take into account correlations beyond mean fields, but we have to determine the model space and then fit the effective interactions with experimental results.
        In this study, a hybrid approach is attempted by applying a method using the Gogny-type density functionals to shell-model calculations. The resultant density-dependent interaction of the shell-model Hamiltonian is self-consistently determined. The goal of the present study is to extend a previous application to the sd-shell region to heavier regions.
        In this presentation, we will present results for the pf-shell nuclei in comparison with the experimental results. In particular, we will focus on the calculation with the isospin-dependent tensor force, and show that the isospin dependence is necessary to describe characteristics in neutron-rich nuclei.

        Speaker: Kota Yoshinaga (Unversity of Tsukuba)
        RPMBT22_indexing_yoshinaga.pdf
      • 17:16
        [Indexing] The rotational mode caused by the pair condensation in nuclei 1m

        Abstract (PDF)

        Speaker: Chisato Ruike (University of Tsukuba)
        ruike_indexing.pdf
      • 17:17
        [Indexing] Superfluid Band Theory for the Neutron Star Inner Crust 1m

        In the inner crust of neutron stars, a Coulomb lattice of nuclei exists, immersed in a sea of superfluid neutron gas. The interplay between these nuclear crystals and the background neutrons may significantly alter nuclear dynamics, a phenomenon known as the "entrainment" effect, which is crucial for understanding several astronomical phenomena.

        In our study, we have developed new self-consistent calculations that fully account for both superfluid effects and band structure effects. We have extracted the "effective mass" of free neutrons through the real-time method.

        In this presentation, we will show the formalism and methodology of our calculations, as well as further extensions towards comprehensive simulations of the subnuclear properties of neutron star matter.

        Speaker: Kenta Yoshimura (Tokyo Institute of Technology)
        RPMBT_Material.pdf
      • 17:18
        [Indexing] Large-scale shell model study of $\mathbf{\beta^-}$-decay properties of $\mathbf {N=126, 125}$ nuclei along the $r$-process path 1m

        The rapid neutron capture process ($r$-process) is the most important mechanism for the synthesis of about half of the elements heavier than iron. It occurs in an environment with relatively high temperatures and high neutron densities. The abundances of the elements created by the $r$-process strongly depend on several nuclear inputs like masses, neutron capture rates, $\beta$-decay rates, and $\beta$-delayed neutron emission probabilities at the waiting point nuclei. Among them, the $\beta$-decay process plays a crucial role in the $r$-process. In this work, we have investigated various nuclear $\beta$-decay properties of $N = 126, 125$ isotones with proton numbers $Z=52-79$ within the framework of the nuclear shell model. This comprehensive analysis considered both Gamow-Teller (GT) and first-forbidden (FF) transitions to evaluate $\beta$-decay rates. We have found that including FF transitions in addition to GT transitions is essential, as they significantly impact the total $\beta$-decay half-lives near $Z = 82$. Additionally, we systematically analyzed the GT strength distributions as a function of proton number. We have observed that the GT strengths at low excitation energies are rather strong on the proton deficient side due to the increasing number of proton holes in the proton $0h_{11/2}$ orbit, which accelerates GT decay. This investigation aims to provide detailed information on $\beta$-decay properties around $A\approx 195$ to understand the distribution of the third $r$-process abundance peak.

        Speaker: Anil Kumar (Center for Computational Sciences, University of Tsukuba, Tsukuba, Japan)
        Anil_Kumar_RPMBT22.pdf
      • 17:19
        [Indexing] Double beta decay phase space factor calculation using Coulomb potential calculated by mean field calculation 1m

        Abstract (PDF)

        Speaker: Atsuya Kanai (University of Tsukuba)
        RPMBTindexing.pdf
      • 17:20
        [Indexing] Evolution of chirality in the electron-positron pair production driven by photons 1m

        Abstract (PDF)

        Speaker: Chengpeng Yu (University of Tsukuba)
        poster-indexing.pdf
      • 17:21
        [Indexing] Automatic Structural Search of Tensor Network States including Entanglement Renormalization 1m

        When the entanglement structure of the quantum state of interest is non-uniform in real space, accurately representing the state with a limited number of degrees of freedom hinges on appropriately configuring the Tensor Network (TN) to align with the entanglement pattern. Although TN states including entanglement renormalization (ER) can encompass a wider variety of entangled states, a proposal has yet to show a structural search of ER due to its high computational cost and the lack of flexibility in its algorithm. In this study, we conducted an optimal structural search of TN, including ER, based on the reconstruction of their local structures with respect to variational energy. Firstly, we demonstrated that our algorithm for the spin-1/2 tetramer singlets model could calculate exact ground energy using the multi-scale entanglement renormalization ansatz (MERA) structure as an initial TN structure. Subsequently, we applied our algorithm to the random XY models with the two initial structures: MERA and the suitable structure underlying the strong disordered renormalization group. We found that, in both cases, our algorithm achieves improvements in variational energy, fidelity, and entanglement entropy. The degree of improvement in these quantities is superior in the latter case compared to the former, suggesting that utilizing an existing TN design method as a preprocessing step is important for maximizing our algorithm's performance.

        Speaker: Ryo Watanabe (Osaka University)
        PRMBT22.pdf
      • 17:22
        [Indexing] Effect of the Coulomb interaction on nuclear deformation and drip lines 1m

        The energy density functional method is able to provide systematic analysis on properties of nuclei all over the nuclear chart.
        We perform the calculations for nuclei from the proton to the neutron drip lines including superheavy nuclei.
        Using HFBTHO program(Axially deformed solution of the Skyrme-Hartree–Fock–Bogoliubov equations using the transformed harmonic oscillator basis (II)), the effect of Coulomb interaction on the detormation of even-even nuclei and drip line is reported.
        The results show that the Coulomb interaction increases the deformation of nuclei in the large mass number range and stretches the drip line toward the neutron side.
        It is interesting to find that the Coulomb interaction gives additional binding to nuclei near the neutron drip line.
        In order to understand microscopic mechanisms of these effects, we plan to report results of calculations with constraints on deformation, radius, etc.

        Speaker: Mr Kenta Hagihara (University of Tsukuba)
        RPMBT22_talk_hagihara.pdf
      • 17:23
        [Indexing] Coulomb interaction-driven entanglement of electrons on helium 1m

        The generation and evolution of entanglement in many-body systems is an active area of research that spans multiple fields, from quantum information science to the simulation of quantum many-body systems encountered in condensed matter, subatomic physics, and quantum chemistry. Motivated by recent experiments exploring quantum information processing systems with electrons trapped above the surface of cryogenic noble gas substrates, this talk will present an theoretical investigation of the generation of motional entanglement between two electrons via their unscreened Coulomb interaction. The model system consists of two electrons confined in separate electrostatic traps which establish microwave-frequency quantized states of their motion. We have computed the motional energy spectra of the electrons, as well as their entanglement, by diagonalizing the model Hamiltonian with respect to a single-particle Hartree product basis. The computational procedure outlined here can be employed for device design and guidance of experimental implementations. In particular, the theoretical tools developed here can be used for fine tuning and optimization of control parameters in future experiments with electrons trapped above the surface of superfluid helium or solid neon.

        The talk is based on the paper "Coulomb interaction-driven entanglement of electrons on helium" by Beysengulov, Schøyen, Bilek, Flaten, Leinonen, et al. [1], which is currently under review.

        [1] https://arxiv.org/abs/2310.04927

        Speaker: Oskar Leinonen (University of Oslo)
        leinonen_poster_indexing.pdf
      • 17:24
        [Indexing] The impact of connectivity in qubit networks and the symmetry in the XY model on the quantum machine learning’s performance 1m

        Abstract (PDF)

        Speaker: Mr Aoi Hayashi (SOKENDAI (The Graduate University for Advanced Studies), Okinawa Institute of Science and Technology, National Institute of Informatics)
        indexing.pdf
      • 17:25
        [Indexing] A Theoretical Study on Spin-Filter Effect in Layered Materials 1m

        Abstract (PDF)

        Speaker: Mr Jin Inoue (Kanazawa University)
        Jin_Inoue.pdf
      • 17:27
        [Indexing] Accurate relativistic exchange energy functional for atomic nuclei 1m

        The shell evolution towards the extreme neutron-to-proton ratio has been a pivotal focus in nuclear physics over recent decades, since it is crucial to understand the effective nucleon-nucleon interactions and the r-process. Significant efforts have been devoted to deciphering the mechanism behind the shell evolution, such as the spin-orbit interaction, the tensor force, and the pseudospin symmetry. This motivates us to include the exchange energy in the relativistic density functional theory to simultaneously consider the important mechanisms in a self-consistent way.

        The inclusion of nucleonic exchange energy has been a long-standing challenge for the relativistic density functional theory in nuclear physics. We propose an orbital-dependent relativistic Kohn-Sham density functional theory to incorporate the exchange energy with local Lorentz scalar and vector potentials. The relativistic optimized effective potential equations for the local exchange potentials are derived and solved efficiently. The obtained binding energies and charge radii for nuclei are benchmarked with the results given by the traditional relativistic Hartree-Fock approach, which involves intractable nonlocal potentials. It demonstrates that the present framework is not only accurate but also efficient. An extension to three-dimensional coordinate space is also realized, which would have great potential for wide applications.

        Speaker: Dr QIANG ZHAO (Research Center for Nuclear Physics, Osaka University)
        RPMBT_QZHAO_presentation.pdf
    • 17:30 → 19:30
      Poster session Kasuga Area, University of Tsukuba

      Kasuga Area, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 17:30
        A Theoretical Study on Spin-Filter Effect in Layered Materials 2h

        Abstract (PDF)

        Speaker: Mr Jin Inoue (Kanazawa University)
        abstract.pdf Jin_Inoue.pdf
      • 17:30
        Accurate relativistic exchange energy functional for atomic nuclei 2h

        The shell evolution towards the extreme neutron-to-proton ratio has been a pivotal focus in nuclear physics over recent decades, since it is crucial to understand the effective nucleon-nucleon interactions and the r-process. Significant efforts have been devoted to deciphering the mechanism behind the shell evolution, such as the spin-orbit interaction, the tensor force, and the pseudospin symmetry. This motivates us to include the exchange energy in the relativistic density functional theory to simultaneously consider the important mechanisms in a self-consistent way.

        The inclusion of nucleonic exchange energy has been a long-standing challenge for the relativistic density functional theory in nuclear physics. We propose an orbital-dependent relativistic Kohn-Sham density functional theory to incorporate the exchange energy with local Lorentz scalar and vector potentials. The relativistic optimized effective potential equations for the local exchange potentials are derived and solved efficiently. The obtained binding energies and charge radii for nuclei are benchmarked with the results given by the traditional relativistic Hartree-Fock approach, which involves intractable nonlocal potentials. It demonstrates that the present framework is not only accurate but also efficient. An extension to three-dimensional coordinate space is also realized, which would have great potential for wide applications.

        Speaker: Dr QIANG ZHAO (Research Center for Nuclear Physics, Osaka University)
      • 17:30
        Coulomb interaction-driven entanglement of electrons on helium 2h

        The generation and evolution of entanglement in many-body systems is an active area of research that spans multiple fields, from quantum information science to the simulation of quantum many-body systems encountered in condensed matter, subatomic physics, and quantum chemistry. Motivated by recent experiments exploring quantum information processing systems with electrons trapped above the surface of cryogenic noble gas substrates, this talk will present an theoretical investigation of the generation of motional entanglement between two electrons via their unscreened Coulomb interaction. The model system consists of two electrons confined in separate electrostatic traps which establish microwave-frequency quantized states of their motion. We have computed the motional energy spectra of the electrons, as well as their entanglement, by diagonalizing the model Hamiltonian with respect to a single-particle Hartree product basis. The computational procedure outlined here can be employed for device design and guidance of experimental implementations. In particular, the theoretical tools developed here can be used for fine tuning and optimization of control parameters in future experiments with electrons trapped above the surface of superfluid helium or solid neon.

        The talk is based on the paper "Coulomb interaction-driven entanglement of electrons on helium" by Beysengulov, Schøyen, Bilek, Flaten, Leinonen, et al. [1], which is currently under review.

        [1] https://arxiv.org/abs/2310.04927

        Speaker: Oskar Leinonen (University of Oslo)
      • 17:30
        Double beta decay phase space factor calculation using Coulomb potential calculated by mean field calculation 2h

        Abstract (PDF)

        Speaker: Atsuya Kanai (University of Tsukuba)
        abstract.pdf
      • 17:30
        Effect of the Coulomb interaction on nuclear deformation and drip lines 2h

        The energy density functional method is able to provide systematic analysis on properties of nuclei all over the nuclear chart.
        We perform the calculations for nuclei from the proton to the neutron drip lines including superheavy nuclei.
        Using HFBTHO program(Axially deformed solution of the Skyrme-Hartree–Fock–Bogoliubov equations using the transformed harmonic oscillator basis (II)), the effect of Coulomb interaction on the detormation of even-even nuclei and drip line is reported.
        The results show that the Coulomb interaction increases the deformation of nuclei in the large mass number range and stretches the drip line toward the neutron side.
        It is interesting to find that the Coulomb interaction gives additional binding to nuclei near the neutron drip line.
        In order to understand microscopic mechanisms of these effects, we plan to report results of calculations with constraints on deformation, radius, etc.

        Speaker: Mr Kenta Hagihara (University of Tsukuba)
      • 17:30
        Evolution of chirality in the electron-positron pair production driven by photons 2h

        Abstract (PDF)

        Speaker: Chengpeng Yu (University of Tsukuba)
        abstract.pdf
      • 17:30
        Large-scale shell model study of $\mathbf{\beta^-}$-decay properties of $\mathbf {N=126, 125}$ nuclei along the $r$-process path 2h

        The rapid neutron capture process ($r$-process) is the most important mechanism for the synthesis of about half of the elements heavier than iron. It occurs in an environment with relatively high temperatures and high neutron densities. The abundances of the elements created by the $r$-process strongly depend on several nuclear inputs like masses, neutron capture rates, $\beta$-decay rates, and $\beta$-delayed neutron emission probabilities at the waiting point nuclei. Among them, the $\beta$-decay process plays a crucial role in the $r$-process. In this work, we have investigated various nuclear $\beta$-decay properties of $N = 126, 125$ isotones with proton numbers $Z=52-79$ within the framework of the nuclear shell model. This comprehensive analysis considered both Gamow-Teller (GT) and first-forbidden (FF) transitions to evaluate $\beta$-decay rates. We have found that including FF transitions in addition to GT transitions is essential, as they significantly impact the total $\beta$-decay half-lives near $Z = 82$. Additionally, we systematically analyzed the GT strength distributions as a function of proton number. We have observed that the GT strengths at low excitation energies are rather strong on the proton deficient side due to the increasing number of proton holes in the proton $0h_{11/2}$ orbit, which accelerates GT decay. This investigation aims to provide detailed information on $\beta$-decay properties around $A\approx 195$ to understand the distribution of the third $r$-process abundance peak.

        Speaker: Anil Kumar (Center for Computational Sciences, University of Tsukuba, Tsukuba, Japan)
      • 17:30
        Nuclear structure study using a hybrid approach of shell model and Gogny-type density functionals 2h

        The Gogny-type density functionals have finite-range and density-dependent terms. The parameters of the functionals are designed not only to reproduce the basic properties of finite nuclei but also to satisfy the saturation properties of nuclear matter. Consequently, calculations using a single density functionals can describe experimental data in various mass regions. However, the mean-field calculations using the functionals miss some corrections. In contrast, there are semi-empirical methods that construct a shell-model Hamiltonian by fitting experimental values. The shell-model (configuration interaction) calculations can take into account correlations beyond mean fields, but we have to determine the model space and then fit the effective interactions with experimental results.
        In this study, a hybrid approach is attempted by applying a method using the Gogny-type density functionals to shell-model calculations. The resultant density-dependent interaction of the shell-model Hamiltonian is self-consistently determined. The goal of the present study is to extend a previous application to the sd-shell region to heavier regions.
        In this presentation, we will present results for the pf-shell nuclei in comparison with the experimental results. In particular, we will focus on the calculation with the isospin-dependent tensor force, and show that the isospin dependence is necessary to describe characteristics in neutron-rich nuclei.

        Speaker: Kota Yoshinaga (Unversity of Tsukuba)
      • 17:30
        Realizing Topological Quantum Walks on NISQ Digital Quantum Computer 2h

        We study the quantum walk on the off-diagonal Aubry-André-Harper (AAH) lattice with periodic modulation using a digital quantum computer. We investigate various initial states at the single-particle level, considering different hopping modulation strengths and phase factors. Initiating the quantum walk with a particle at the lattice edge reveals the robustness of the edge state, attributed to the topological nature of the AAH model, and displays the influence of the phase factor on this edge state. On the other hand, when the quantum walk begins with a particle in the lattice bulk, we observe a repulsion of the bulk walker from the edge, especially under strong hopping modulation. Furthermore, we extend our investigation to the quantum walk of two particles with nearest-neighbour (NN) interaction. We show the repulsion effect in the quantum walk when two walkers originate from the edge and bulk of the lattice due to the interaction. Additionally, when two particles are positioned at NN sites and subjected to strong hopping modulation strength, they exhibit localization in the presence of interaction. We analyze these phenomena by examining physical quantities such as density evolution, two-particle correlation, and participation entropy, and discuss their potential applications in quantum technologies.

        Speaker: Dr Mrinal Kanti Giri (National Tsing-Hua University)
        Tsukuba_poster_MKG.png
      • 17:30
        Self-consistent renormalization theory of anisotropic spin fluctuations in nearly ferromagnetic metals 2h

        Abstract (PDF)

        Speaker: Prof. Rikio Konno (Kindai University Technical College )
        abstract.pdf
      • 17:30
        Shape fluctuation in low-lying states in $N \approx 40$ neutron-rich nuclei 2h

        Abstract (PDF)

        Speaker: Kouhei Washiyama (University of Tsukuba)
        abstract.pdf
      • 17:30
        Superfluid Band Theory for the Neutron Star Inner Crust 2h

        In the inner crust of neutron stars, a Coulomb lattice of nuclei exists, immersed in a sea of superfluid neutron gas. The interplay between these nuclear crystals and the background neutrons may significantly alter nuclear dynamics, a phenomenon known as the "entrainment" effect, which is crucial for understanding several astronomical phenomena.

        In our study, we have developed new self-consistent calculations that fully account for both superfluid effects and band structure effects. We have extracted the "effective mass" of free neutrons through the real-time method.

        In this presentation, we will show the formalism and methodology of our calculations, as well as further extensions towards comprehensive simulations of the subnuclear properties of neutron star matter.

        Speaker: Kenta Yoshimura (Tokyo Institute of Technology)
      • 17:30
        The Hubbard- and van der Waals-corrections on the DFT calculations of epsilon-zeta transition pressure in solid oxygen 2h

        In this study, we consider the treatments of short-range and long-range interactions in solid oxygen at the epsilon-zeta phase transition using the Hubbard U and van der Waals dispersion, respectively. We show that the London dispersion may correctly capture the nonlocal interactions in solid oxygen instead of the Hartree-Fock exchange [1]. The nonlocal effect is expected to be dominant at below 20 GPa. A correct treatment of the local and nonlocal interactions on an equal footing is, thus, important to study the solid oxygen. A comparison of a direct van der Waals correction vdW-D and nonlocal two-body correlation functionals vdW-DF with the nonlocal Hartree-Fock exchange in hybrid functionals [2] will be presented.

        References
        [1] Le The Anh, Phys. Chem. Chem. Phys. 25, 25654 (2023).
        [2] A. J. Ochoa-Calle, Chem. Theory Comput. 11, 3 (2015).

        Speaker: Dr The Anh Le (Outsourcer, Quemix Inc., 2-11-2 Nihonbashi, Chuo-ku, Tokyo 103-0027)
        poster-A0.pptx
      • 17:30
        The impact of connectivity in qubit networks and the symmetry in the XY model on the quantum machine learning’s performance 2h

        Abstract (PDF)

        Speaker: Mr Aoi Hayashi (SOKENDAI (The Graduate University for Advanced Studies), Okinawa Institute of Science and Technology, National Institute of Informatics)
        abstract.pdf
      • 17:30
        The rotational mode caused by the pair condensation in nuclei 2h

        Abstract (PDF)

        Speaker: Chisato Ruike (University of Tsukuba)
        abstract.pdf RPMBT.pdf
      • 17:30
        Variational method with an explicit energy functional for neutron matter at finite temperature taking into account the spin-orbit force 2h

        Abstract (PDF)

        Speaker: Kento Kitanaka (Department of Physics and Applied Physics, Waseda Univesity)
        abstract.pdf
      • 17:30
        Variational method with an explicit energy functional for symmetric nuclear matter taking into account the spin-orbit force 2h

        Abstract (PDF)

        Speaker: Toshiya Osuka (Department of Physics and Applied Physics, Waseda University)
        abstract.pdf
    • 20:00 → 22:00
      Students' dinner: Gathering Bistro Polizza (Bistro Polizza)

      Bistro Polizza

      Bistro Polizza

      Event only for students.

      Convener: Kenta Hagihara
  • Wednesday, 25 September
    • 09:20 → 10:40
      Session: Quantum chemistry, atomic and molecular physics (Chair: BISHOP, Raymond) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 09:20
        Quantum computations of relativistic and many-body effects in atomic and molecular systems based on variational algorithms 30m

        Quantum computations of relativistic and many-body effects in atomic and molecular systems based on variational algorithms

                                                                          Bhanu Pratap Das
                                           Centre for Quantum Engineering Research and Education
                              TCG Centres for Research and Education in Science and Technology
                                                                                  Kolkata, India

                                                       Department of Physics, School of Science
                                                                 Tokyo Institute of Technology
                                                                                   Tokyo, Japan

        In this talk, I shall present results of our recent computations of relativistic and many-body effects in atomic and molecular systems on digital quantum computers and also the D-wave quantum annealer. The variational quantum eigensolver (VQE) was used to compute the hyperfine interaction constants for atomic systems and the dipole moments of molecular systems on superconducting and trapped ion platforms respectively. The ground-state energies were obtained as a byproduct of the calculations for both the cases and were determined to within one per cent of the classical computations. The corresponding errors for the hyperfine interaction constants and the molecular dipole moments were found to be larger. The interplay of relativistic and many-body effects for all the properties will be discussed.

        Finally, the results for the fine-structure intervals in boron-like ions using the quantum annealer eigensolver (QAE) will be presented. This quantity is relativistic in origin, but is influenced by many-body effects. We have computed it to an accuracy of 99% on the D-wave annealer compared to high precision laboratory measurements. The reasons for achieving this high accuracy will be explained.

        Speaker: Prof. Bhanu Das (TCG CREST)
        Das-RPMBT22.pdf newDas-RPMBT22.pdf
      • 09:50
        New Analytical Representation for Electronic Terms of Nuclear Schiff Moment 30m

        The nuclear Schiff moment (NSM) is produced by a nuclear force that simultaneously violates charge conjugation (C) symmetry and spatial parity (P) inversion symmetry. The experimental detection of NSM is significant as CP violation is crucial for explaining the current matter-dominated universe. Measuring NSM in molecules necessitates precise experiments and theoretical calculations that incorporate both electronic and nuclear wavefunctions. Conventionally, electronic terms have been approximated using a first-order power series expansion of the electronic radial function; however, this may not be sufficiently accurate. In this study, we introduce a new accurate analytical expression for the electronic terms using Gaussian basis sets, which avoids any truncation of the power series. For the RaO molecule, a prime candidate for NSM observation, conventional methods overestimated the electronic terms by more than 50%, underscoring the significance of our analytical approach.

        Speaker: Dr Minori Abe (Hiroshima University)
        Minori_Abe.pdf
    • 10:25 → 10:55
      Coffee break 30m Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
    • 10:55 → 12:20
      Session: Computational many-body physics (Chair: CHIN, SIU) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 10:55
        Tensor networks and new classical heuristics 30m

        I will discuss
        (i) some recent progress to improve the expressivity of tensor networks
        (ii) the rate of convergence of tensor network calculations and the error dependence of this classical heuristics
        (iii) some new classical algorithms for many-body systems motivated by noisy quantum simulation.

        Speaker: Garnet Kin-Lic Chan (California Institute of Technology)
      • 11:25
        Tensor network toward the lattice QCD 30m

        Tensor networks provide a new approach to studying quantum many-body problems. In particle physics, tensor networks are attracting attention as a novel numerical method, particularly for lattice theories with the sign problem. In this talk, recent progress in tensor networks for particle physics, toward their future applications to the lattice QCD, will be discussed.

        Speaker: Shinichiro Akiyama (University of Tsukuba)
        akiyama.pdf
      • 11:55
        Overcoming Fermionic Sign Problem in Lattice Quantum Monte Carlo: A Cuprate Case 25m

        We developed a strong coupling perturbation scheme for general Hubbard model around half-field particle-hole symmetric reference system [1]. The approach based on a lattice determinatal Quantum Monte Carlo method in continuous and discrete time versions [2] for a large periodic clusters in a fermionic bath. The first and second order perturbation in the shift of chemical potential and long-range hopping gives a reasonable accuracy for parameters corresponding to the optimal cuprate systems. We calculate spectral function of doped t-t'-U model for interaction strength equal to the band width and discuss a mechanism of the pseudogap formation. Results for standard cuprates model with U=8t=W and t'/t=-0.3 for the temperature of the order of T=0.1t show formation of the Fermi-arcs. We discuss the magnetic and superconducting instability using symmetry broken external fields.

        [1] S. Iskakov, M. I. Katsnelson, A. I. Lichtenstein, npj Comp. Materials 10, 36 (2024).
        [2] E. Gull, A. J. Millis, A. I. Lichtenstein, et. al., Rev. Mod. Phys. 83, 349 (2011).

        Speaker: Alexander Lichtenstein (University of Hamburg)
        Lichtenstein_RPMBT22.pdf
    • 14:00 → 17:00
      Free discussion
  • Thursday, 26 September
    • 09:00 → 10:30
      Session: Quantum information and computing (Chair: YUNOKI, Seiji) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 09:00
        Continuous-variable optimization: quantum vs classical 30m

        Performance of quantum annealing for functions with continuous variables has not been well studied. We evaluate quantum annealing on a continuous-variable function with a rugged energy landscape, using domain-wall encoding to map continuous to discrete variables. We assess several algorithms and hardware, including D-Wave 2000Q, TEBD, simulated annealing, and simulated quantum annealing. TEBD's coherent quantum annealing significantly outperforms the others, demonstrating effective coherent tunneling. These results suggest that with reduced thermal noise in the hardware, quantum annealing hardware will surpass classical algorithms.

        Speaker: Prof. Hidetoshi Nishimori (Tokyo Institute of Technology)
        nishimori.pdf
      • 09:30
        Quantum many-body scars in dual-unitary circuits 30m

        Dual-unitary circuits are a class of quantum systems for which exact calculations of various quantities are possible, even when the system is chaotic. The array of known exact results paints a picture of dual-unitary circuits as rapidly thermalising systems. However, we present a method to construct dual-unitary circuits for which some simple initial states fail to thermalise, despite the circuits being "maximally chaotic", ergodic and mixing. This is achieved by embedding quantum many-body scars in the circuit. We support our analytic results with numerical simulations showing the stark contrast in the rate of entanglement growth from an initial scar state compared to non-scar initial states. Our results are well suited to an experimental test, due to the compatibility of the circuit layout with the native structure of current digital quantum simulators.

        Speaker: Shane Dooley (Dublin Institute for Advanced Studies (DIAS))
        2024_09_26_Tsukuba_RPMBT22.pdf
      • 10:00
        Quantum many-body dynamics in digital quantum computers 30m

        Owning to the recent rapid advancement of quantum technologies, digital quantum computers with more than 100 qubits have emerged as a new platform to explore quantum many-body dynamics that may potentially be out of reach for classical computers. In this talk, I will introduce some of the recent progress in this direction and present our recent studies. In particular, I will discuss our recent investigation of the dynamics of periodically driven systems using an IBM Quantum Heron processor, focusing on the emergence of discrete time crystals (DTCs) and discrete time quasicrystals (DTQCs) in two spatial dimensions [1]. Our study, based on a kicked Ising model with 133 qubits, reveals a prethermal regime characterized by magnetization oscillations. We observe period-doubling DTCs and discover DTQCs induced by the longitudinal field. Our findings, supported by classical simulations based on state vector methods as well as tensor network methods, shed light on out-of-equilibrium dynamics in quantum systems and highlight the potential of digital quantum computers for studying many-body systems.
        [1] K. Shinjo, K. Seki, T. Shirakawa, R.-Y. Sun, and S. Yunoki, “Unveiling clean two-dimensional discrete time quasicrystal on a digital quantum computer”, arXiv:2403.16718.

        Speaker: Seiji Yunoki (RIKEN)
    • 10:30 → 11:00
      Coffee break 30m Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
    • 11:00 → 12:20
      Session: Condensed matter physics (Chair: ARITA, Ryotaro) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 11:00
        Chester supersolid in dipolar interlayer exciton condensates 30m

        We have predicted in an electron-hole bilayer semiconductor system using a variational approach, a transition from an exciton superfluid to an incompressible “Chester supersolid”, which has occupancy of one on each lattice site [1].

        By solving the full Gross-Pitaevskii equation for this 2D system, we carry out a complete investigation of the time-dependent dynamic exciton supersolid. Here, the interaction between the excitons is purely repulsive and dipolar-like, in marked contrast with ultracold dipolar gases, where the stability is driven by an additional effective attractive interaction[2]. We extend the Gross-Pitaevskii formalism to include the strong two-particle correlations[3], and to exclude the self-interaction energy which is absent for one-particle occupancy per supersolid site[4].

        We present solutions of the Gross-Pitaevskii equation for a range of accessible experimental parameters which are the electron-hole layer separation and the exciton density.

        References
        [1]S. Conti, A. Perali, A. R. Hamilton, M. V. Milošević, F. M. Peeters, and D. Neilson, Phys. Rev. Lett. 130, 057001 (2023).
        [2] A. Alaña, I. L. Egusquiza, and M. Modugno, Phys. Rev. A 108, 033316 (2023).
        [3] G. E. Astrakharchik, J. Boronat, I. L. Kurbakov, and Yu. E. Lozovik, Phys. Rev. Lett. 98, 060405 (2007).
        [4] P. W. Anderson, J. Low Temp. Phys. 169, 124–132 (2012).

        Speaker: Dr Sara Conti (University of Antwerp, Antwerp, Belgium)
        SaraConti.pdf
      • 11:30
        Avalanche Instability as Nonequilibrium Quantum Criticality 25m

        A fundamental instability in the nonequilibrium conduction band under an
        electric field bias occurs via the spontaneous emission of coherent
        phonons. Analytic theory, supported by numerical calculations,
        establishes that the quantum avalanche, an abrupt nonequilibrium
        occupation of excited bands, results from the competition between the
        collapse of the band minimum via the phonon emission and the dephasing
        of the electron with the environment. The continuous avalanche
        transition is a quantum phase transition with the nonequilibrium phase
        diagram determined by the avalanche parameter $\beta$. We further
        confirm the nature of the quantum avalanche with the temperature
        dependence.

        [1] X. Chen and J. E. Han, Avalanche Instability as Nonequilibrium
        Quantum Criticality, Phys. Rev. B 109, 054307 (2024).
        [2] J. E. Han et al, Correlated insulator collapse due to quantum
        avalanche via in-gap ladder states, Nat. Comm. 14, 2936 (2023).
        [3] J. Nathawat et al, Signatures of hot carriers and hot phonons in the
        re-entrant metallic and semiconducting states of Moiré-gapped graphen,
        Nat. Comm. 14, 1507 (2023).

        Speaker: Jong Han (SUNY at Buffalo)
        RPMBT22.pdf
      • 11:55
        In Search of an Organizing Principle for Quantum Hall Systems 25m

        I will describe connections between ground states of quantum Hall Hamiltonians with multiple-Landau-level orbitals, whose excitations display either Abelian or non-Abelian braiding statistics, and (non-holomorphic) symmetric polynomials. In the case of two-body interactions, these represent parton states. The emergent Entangled Pauli Principle (EPP), which defines the “DNA” of the quantum Hall fluid state, is behind the exact determination of the topological characteristics of those vacua, including charge and braiding statistics of excitations, and effective edge theory descriptions. This DNA admits a tensor network structure of finite bond dimension that emerges via root level entanglement and encodes all universal properties of the fluid. I will also present recent work connecting these findings to the so-called "strange metal", a compressible critical state of matter with a hyperdegenerate ground state subspace and no Landau quasiparticles.

        Speaker: Prof. Gerardo Ortiz (Indiana University and Institue for Advanced Study, Princeton)
        RPMBT-22-CMP.key
    • 14:00 → 14:55
      Session: Non-equilibrium many-body phenomena (Chair: HAN, Jong) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 14:00
        Quasi-steady state descriptions for photo-doped Mott insulators 30m

        Doping charge carriers into Mott insulators provides a pathway to produce intriguing emergent phenomena [1]. In equilibrium systems, doping can be chemically controlled. On the other hand, photo-doping, where particles are excited across the Mott gap, provides an alternative way. Compared to chemical-doping, photo-doping creates a wider variety of charge carriers, which may lead to the emergence of fascinating nonequilibrium states. In particular, when the gap is large, the lifetime of photo-carriers is exponentially enhanced, leading to quasi-steady states after intraband cooling of photo-carriers.

        In this talk, we introduce two types of theoretical descriptions to systematically explore quasi-steady states of photo-doped Mott insulators [1]. The first approach is the so-called nonequilibrium steady state approach, where we approximate a photo-doped state as a nonequilibrium steady state stabilized by external baths. The second approach is the quasi-equilibrium approach, where we treat a photo-doped state as an equilibrium state of an effective model using the generalized Gibbs ensemble. In the first part, we explain the idea of these approaches and their relations, providing the overview of relevant works. In the second part, we discuss the concrete application of the quasi- equilibrium approach to the 1D extended Hubbard model [2,3]. Using numerical and analytical methods, we show the emergence of the so-called η-pairing phase and the string charge-density- wave phase in the photo-doped Mott insulators. In particular, we show that the wave function of photo-doped states in the large on-site interaction limit can be exactly expressed as $|\Psi\rangle = |\Psi_{\rm charge}\rangle|\Psi_{\rm spin}\rangle|\Psi_{\rm \eta-spin}\rangle$, which indicates the separation of spin, charge and η−spin degrees of freedoms. Here η−spin represents the type of the photo-carriers, i.e. doublons and holons. This state is analogous to the celebrated Ogata-Shiba state of the doped Hubbard model in equilibrium. The expression provides us useful insight into the origin and properties of the photo-doped states. Our results demonstrate that the emergent degrees of freedom activated by photo-doping can lead to intriguing quantum states absent in equilibrium.

        [1] Y. Murakami, D. Golež, M. Eckstein, P. Werner, arXiv:2310.05201 (a review paper).
        [2] Y. Murakami, S. Takayoshi, T. Kaneko, Z. Sun, D. Golež, A. J. Millis, P. Werner, Comm. Phys. 5, 23 (2022).
        [3] Y. Murakami, S. Takayoshi, T. Kaneko, A. Läuchli, P. Werner, Phys. Rev. Lett. 130, 106501 (2023), Editors’ suggestion.

        Speaker: Dr Yuta Murakami (RIKEN, CEMS)
        Yuta_Murakami.pdf
      • 14:30
        Electron-phonon coupling effect on the vibrational relaxation of CO on Pd(111) 25m

        The internal stretch mode of polar molecules adsorbed on metallic surfaces has emerged as an exceptional test-bed in which to probe many-body theories in current state-of-the-art time-revolved spectroscopy experiments. Here we study non-adiabatic effects on the internal stretch mode of CO adsorbed on the Pd(111) surface by means of first principles calculations [1, 2]. The theoretical
        treatment that we employ, including electron-hole pair excitations and electron-mediated coupling between the vibrational modes [3, 4], allows us to study the internal stretch mode under thermal and non-thermal conditions. The latter permits to simulate the conditions that a femtosecond infrared pump pulse generates on the system and to predict the transient red-shift and change in the linewidth
        that are induced. The laser-induced non-thermal electron and phonon distributions are described, respectively, by Fermi-Dirac and Bose-Einstein distributions defined by time-dependent electronic Te(t) and lattice Tl(t) temperatures are calculated with a two temperature model (TTM).

        [1] R. Bombín, A. S. Muzas, D. Novko, J. I. Juaristi and M. Alducin, Anomalous transient blueshift in the internal stretch mode of CO/Pd(111), Phys. Rev. B 107, L121404 (2023)
        [2] R. Bombín, A. S. Muzas, D. Novko, J. I. Juaristi, M. Alducin, Vibrational dynamics of CO on Pd(111) in and out of thermal equilibrium, Phys. Rev. B 108, 045409 (2023)
        [3] D. Novko., M. Alducin and J. I. Juaristi, J. I. Juaristi, Electron-Mediated Phonon-Phonon Coupling Drives the Vibrational Relaxation of CO on Cu(100), Phys. Rev. Lett. 120, 156804 (2018).
        [4] D. Novko, J. C. Tremblay, M. Alducin, J. I. Juaristi, Ultrafast Transient Dynamics of Adsorbates on Surfaces Deciphered: The Case of CO on Cu(100), Phys. Rev. Lett. 122, 016806 (2018).

        Speaker: Raúl Bombín Escudero (Université de Bordeaux)
        CO_on_Pd.pdf
    • 14:55 → 15:25
      Coffee break 30m Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
    • 15:25 → 17:15
      Award session: Award session (Chair: REINHOLZ, Heidi) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 15:25
        Laudatio Feenberg 10m
        Speaker: Gerardo Ortiz (Indiana University and Institue for Advanced Study, Princeton)
        Laudatio-QFTM.key
      • 15:35
        Intertwined Orders and the Physics of High Temperature Superconductors 30m

        Complex phase diagrams are generic feature of quantum materials that display high temperature superconductivity. In addition to d-wave superconductivity (or other unconventional states), these phase diagrams typically include various forms of charge-ordered phases, including charge-density-waves and/or spin-density waves, and electronic nematic states. In most cases these phases have critical temperatures comparable in magnitude to that of the superconducting state,and appear in a "pseudo-gap" regime. In these systems the high temperature state is not a good metal with well-defined quasiparticles but a "strange metal". These states typically arise from doping a strongly correlated Mott insulator. With my collaborators we have identified these behaviors as a problem with "Intertwined Orders". A Pair-density wave is a type of superconducting state which embodies the physics of intertwined orders. In this lecture I will discus the phenomenology of intertwined orders and the quantum materials that are known to display these behaviors.

        Speaker: Prof. Eduardo Fradkin (Department of Physics and Anthony J. Leggett Institute for Condensed Matter Theory)
        fradkin-2024-feenberg.pdf
      • 16:05
        Majorana fermions in condensed matter physics. Examples 30m

        In this lecture I will concentrate on Majorana fermions as collective excitations and consider two examples related to my own research. The first is the 2-channel Kondo effect where Majorana zero mode emerges as a remnant of the overscreened impurity spin, and the other is the solvable model of 3D Kondo lattice where Majorana fermions of the spin liquid create bound states with conduction electrons giving rise to an exotic superconductivity.

        Speaker: Alexei Tsvelik (Brookhaven National Laboratory)
        TsukubaTalk.pptx
      • 16:35
        Laudatio Kuemmel 10m
        Speaker: Prof. Jordi Boronat (Universitat Politècnica de Catalunya)
        kuemel.pdf
      • 16:45
        Diagrammatic Monte Carlo for the Hubbard model 30m

        In this talk I will describe our recent progress in the development of Diagrammatic Monte Carlo techniques for the two-dimensional Fermi-Hubbard model. I will describe how correlations can lead to qualitative changes in the Fermi surface, or to a selective destruction of quasiparticle excitations near the antinodes in the pseudogap regime.

        Speaker: Riccardo Rossi (École Polytechnique Fédérale de Lausanne, Switzerland)
        2024-09-26_rpmbt-22-tsukuba-riccardo-rossi-presentation.pdf
    • 18:30 → 21:00
      Conference dinner Imperial Room (Hotel Grand Shinonome)

      Imperial Room

      Hotel Grand Shinonome

      Onozaki 488-1, Tsukuba 305-0034

      Access to Hotel Grand Shinonome

  • Friday, 27 September
    • 09:00 → 10:20
      Session: Quantum fluids and cold atoms (Chair: BORONAT, Jordi) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 09:00
        Bose mixtures at finite temperature: magnetism and condensation phenomena 30m

        I will review recent works on the study of both repulsive and attractive Bose mixtures at finite temperature using exact path-integral quantum Monte-Carlo numerical methods. Repulsive mixtures in the quantum degenerate regime undergo a first-order ferromagnetic transition as a function of the interspecies coupling constant. The magnetic behavior close to the point of phase separation is found to contradict predictions based on mean-field and perturbative theories. Attractive mixtures are investigated focusing on the regime of interspecies interactions where the ground state is in a self-bound liquid phase, stabilized by beyond mean-field effects. Calculations of the isothermal curves in the pressure vs density plane are reported for different values of the attraction strength and the extent of the coexistence region between liquid and vapor is established. A similar behavior is observed both in 3D and 2D geometries. In particular, the transition to the superfluid state occurs in a discontinuous way as the density jumps from the gas to the liquid phase. Furthermore, in 3D, the line of first-order transition terminates at a tricritical point and in 2D a relevant role in the gas-liquid transition is played by the quantum scale anomaly. The experimental relevance of these findings is also discussed.
        References:
        1) Phase separation in binary Bose mixtures at finite temperature, G. Spada, L. Parisi, G. Pascual, N. G. Parker, T. P. Billam, S. Pilati, J. Boronat and S. Giorgini, SciPost Phys. 15, 171 (2023).
        2) Attractive solution of binary Bose mixtures: liquid-vapour coexistence and critical point, G. Spada, S. Pilati and S. Giorgini, Phys. Rev. Lett. 131, 173404 (2023).
        3) Quantum droplets in two-dimensional Bose mixtures at finite temperature, G. Spada, S. Pilati and S. Giorgini, preprint, arXiv:2405.09368.

        Speaker: Stefano Giorgini (BEC Center, University of Trento and CNR-INO)
        RPMBT22-Tokyo.pdf
      • 09:30
        Vortices in a dipolar superfluid of interlayer excitons in bilayer semiconductors 25m

        Abstract (PDF)

        Speaker: Prof. David Neilson (University of Antwerp, Antwerpen, Belgium)
        abstract.pdf David.Neilson.pdf
      • 09:55
        The two body density matrix of a Tomonaga Luttinger liquid 25m

        The n-body reduced density matrix (n-RDM) characterizes higher order correlations in an interacting many-body system. This quantity can be used to compute any n-body observable without direct access to the full wavefunction, and is experimentally measurable. The problem of computing higher order density matrices becomes increasingly challenging as the number of local operators grows. However, within the Tomonaga Luttinger liquid regime, bosonization provides access to correlation functions by representing them as exponentials of bosonic field operators that are analytically tractable, even in finite size systems. In this talk we present a detailed analysis of the 2-RDM for an interacting one dimensional fermionic system including both diagonal matrix elements (corresponding to density-density correlations) as well as off-diagonal components which demonstrate how coherences are affected by the interplay of interactions and indistinguishability. As an application we analyze density matrix renormalization group results for the J-V model of interacting, spinless fermions in one dimension in the low-energy sector and use our 2-RDM to compute two-body observables.

        Speaker: Prof. Adrian Del Maestro (University of Tennessee, Knoxville)
        Adrian_DelMaestro_2rdm.pdf
    • 10:20 → 10:50
      Coffee break 30m Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
    • 10:50 → 12:40
      Session: Nuclear and computational many-body physics (Chair: SEDRAKIAN, Armen) Kasuga Auditorium

      Kasuga Auditorium

      Kasuga Campus, University of Tsukuba

      Tsukuba, Ibaraki, 305-8550, Japan
      • 10:50
        Variational Theory and Parquet Diagrams for Nuclear Systems: A Comprehensive Study of Neutron Matter 30m

        Abstract (PDF)

        Speaker: Prof. Eckhard Krotscheck (University at Buffalo SUNY)
        abstract.pdf Krotscheck.pdf Krotscheck.pdf
      • 11:20
        An application of the shift-invert Lanczos method to the non-equilibrium Green's function method 25m

        Describing transport properties of a many-body fermionic system is one of the most important topics in many fields of physics and chemistry.
        To simulate the electronic properties of nanodevices, the non-equilibrium Green function method (NEGF) has been widely employed.
        However, this method suffers from substantial numerical costs for a calculation of the Green function.
        To overcome this problem, we propose a novel approach to significantly reduce the numerical cost of the NEGF by utilizing the shift-invert Lanczos method, where eigenstates of a Hamiltonian in the middle of the spectrum are selectively calculated.
        We apply this procedure to model Hamiltonians for induced-fission reactions and demonstrate its effectiveness.
        For instance, for a Hamiltonian with 66103 dimensions, we find that this method reduces the computation time by about a factor of 30 compared to a direct evaluation.

        Speaker: Kotaro Uzawa (Kyoto University)
        uzawa.pdf
      • 11:45
        A novel method for extracting and emulating continuum physics of finite quantum systems 25m

        The so-called reduced basis method from the field of model order reduction is being actively adapted in studying nuclear many-body bound states. It provides fast and accurate interpolations (or emulations) of the expensive many-body calculations in the input parameter space. These emulators are efficient interfaces through which users can effortlessly access these calculations.

        In this talk, I will discuss my recent studies on generalizing the method to deal with the continuum problems in finite quantum systems (e.g., nuclei or molecules). Two approaches have been developed. The so-called real-energy emulation of the continuum calculations is viable for few-body systems. The other, called complex-energy emulation, works in the energy complex plane. The latter method could be used to extract many-body continuum physics (including scattering, response, and resonances) from bound-state-like calculations. Moreover, it can emulate these extractions in the model input parameter space (e.g., Hamiltonian parameters). I will also briefly mention intriguing connections between the complex-energy emulation and recent progress in studying optimal rational approximation as a numerical analytical continuation method.

        Speaker: Xilin Zhang (Facility for Rare Isotope Beams, Michigan State University)
        Xilin_Zhang_RPMBT_2024_split.pdf
      • 12:10
        Closing 5m

        Proceedings
        RPMBT23

        RPMBT23_Milano.pdf Sedrakian_proc.pdf
    • 14:00 → 17:00
      Free discussion
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