“Quantum-like Modeling” in Biology, Cognitive & Social Sciences

January 26 (Fri) at 9:30 - 17:00, 2024

Venue: Okochi Hall (Main Venue) / via Zoom

Event Official Language: Japanese

Quantum Enhancement in Dark Matter Detection with Quantum Computation

January 22 (Mon) at 16:00 - 18:00, 2024

Thanaporn Sichanugrist (Ph.D. Student, Graduate School of Mathematical Sciences, The University of Tokyo)
Shion Chen (Project Assistant Professor, International Center for Elementary Particle Physics (ICEPP), The University of Tokyo)

Title: Wave-like Dark Matter Search Using Qubits Abstract: The rapid controllability required for quantum computers makes the currently proposed quantum bit modalities also attractive as electromagnetic field sensors. One of the promising applications is wave-like dark matter searches, where the electric field converted from the coherent dark matter excites the qubits, leading to detectable signals [Phys. Rev. Lett. 131, 211001]. The quantum coherence between the qubits can be utilized to enhance the signal rate in a multi-qubit system. By designing an appropriate quantum circuit to entangle the qubits, it was found that the signal rate can scale proportionally to $n_q^2$, with $n_q$ being the number of sensor qubits, rather than linearly with $n_q$ [arXiv: 2311.10413]. In the seminar, we overview the theoretical framework of the search, elaborate on the signal-enhancing mechanism driven by quantum entanglement with specific examples of the quantum circuits, and discuss how the scheme can be implemented in the platform of future fault-tolerant quantum computers. We also provide the introduction of the experimental realization, and report the status of the experimental works carried out in UTokyo/ICEPP.

Venue: via Zoom

Event Official Language: English

Knot Theory in Doubly Periodic Tangles and Applications

January 19 (Fri) at 15:00 - 16:30, 2024

Sonia Mahmoudi (Assistant Professor, Mathematical Science Group, Advanced Institute for Materials Research (AIMR), Tohoku University)

Doubly periodic entangled structures offer an interesting framework for modeling and investigating diverse materials and physical phenomena, from micro to large scales. Specifically, a doubly periodic tangle (DP tangle) is characterized as an embedding of an infinite number of curves in the thickened plane, derived as the lift of a link in the thickened torus to the universal cover. DP tangles play a crucial role in scientific research, particularly in fields such as materials science, molecular chemistry, and biology. Despite their widespread applications, a universally accepted mathematical description of DP tangles is currently lacking. One of the key challenges arises from the infinite possibilities in choosing a periodic cell (referred to as a motif) for a DP tangle, taking into account various periodic boundary conditions. In this presentation, we conduct a comprehensive examination of the concept of topological equivalence of DP tangles, offering insights into potential classifications and applications in the process.

Venue: Hybrid Format (3F #359 and Zoom), Main Research Building

Event Official Language: English

Quantum features in cosmological perturbations?

January 18 (Thu) at 14:15 - 15:00, 2024

Amaury Micheli (Postdoctoral Researcher, iTHEMS)

The statistical properties of the CMB anisotropies, reflecting the curvature inhomogeneities in the very early Universe, are very well accounted for by assuming that the inhomogeneities come from amplified vacuum fluctuations. This scenario makes the cosmological perturbations a possible observational window on the interplay between quantum degrees of freedom and gravity. I will review the discussions on the current presence or absence of quantum features in the perturbations, emphasising the quantum information approaches to this question, and comment on the observability of these features.

Venue: Hybrid Format (3F #359 and Zoom), Main Research Building

Event Official Language: English

Gravitational lensing on superposed curved spacetime

January 18 (Thu) at 13:30 - 14:15, 2024

Youka Kaku (Ph.D. Student, Graduate School of Science, Nagoya University)

In 2017, Bose et al. proposed a tabletop experiment to observe the gravitational effect induced by a spatially superposed mass source, particularly gravity-induced entanglement. This experiment is expected to be the first step in exploring the quantum nature of gravity. Also, there are ongoing efforts to extend their proposal to the relativistic region to observe the unique quantum nature of gravity. In this talk, I will investigate gravitational lensing in a weak gravitational field induced by a spatially superposed mass source. I will show the Einstein ring image of a quantum scalar field propagated on a superposed curved spacetime and compare it with the image of the semi-classical gravity case. This work is currently in progress and is a collaboration with Yasusada Nambu.

Venue: Hybrid Format (3F #359 and Zoom), Main Research Building

Event Official Language: English

Bayesian mechanics of classical, neural, and quantum systems

January 17 (Wed) at 16:30 - 17:45, 2024

Takuya Isomura (Unit Leader, Brain Intelligence Theory Unit, RIKEN Center for Brain Science (CBS))

(This is a joint seminar with iTHEMS Biology group.) Bayesian mechanics is a framework that addresses dynamical systems that can be conceptualised as Bayesian inference. However, the elucidation of requisite generative models is required for empirical applications to realistic self-organising systems. This talk introduces that the Hamiltonian of generic dynamical systems constitutes a class of generative models, thus rendering their Helmholtz energy naturally equivalent to variational free energy under the identified generative model. The self-organisation that minimises the Helmholtz energy entails matching the system's Hamiltonian with that of the environment, leading to an ensuing emergence of their generalised synchrony. In short, these self-organising systems can be read as performing variational Bayesian inference of the interacting environment. These properties have been demonstrated with coupled oscillators, simulated and living neural networks, and quantum computers. This notion offers foundational characterisations and predictions regarding asymptotic properties of self-organising systems exchanging with the environment, providing insights into potential mechanisms underlying emergence of intelligence.

Venue: Seminar Room #359 (Main Venue) / via Zoom

Event Official Language: English

Methods for neural decoding using machine learning, deep learning, and quantum-inspired algorithms

January 17 (Wed) at 15:00 - 16:15, 2024

Kei Majima (Researcher, National Institutes for Quantum Science and Technology (QST))

Note: The format of this event has changed from hybrid to Zoom only. However, you will still be able to watch it on the screen in Room #359 of the Main Research Building. (This is a joint seminar with iTHEMS Biology group.) Recent advances in machine learning have enabled the extraction of intrinsic information from neural activities, a field known as neural decoding. In this presentation, I will introduce several machine learning methods recently developed for neural decoding analysis: 1) a method for visualizing subjective images in the human mind based on brain activity [1], 2) a supervised algorithm designed for predicting discrete ordinal variables [2], and 3) a fast classical algorithm algorithm inspired by quantum computation for approximating principal component analysis (PCA) and canonical correlation analysis (CCA), potentially allowing for the analysis of vast-dimensional neural data [3]. Following these presentations, I am eager to engage in discussions with participants at the RIKEN Quantum Seminar regarding potential collaborations.

Venue: via Zoom

Event Official Language: English

Dust-driven instabilities in protoplanetary disks: toward understanding formation of planetesimals

January 17 (Wed) at 10:30 - 11:30, 2024

Ryosuke Tominaga (Special Postdoctoral Researcher, Star and Planet Formation Laboratory, RIKEN Cluster for Pioneering Research (CPR))

Planet formation starts from collisional growth of sub-micron-sized dust grains in a gas disk called a protoplanetary disk. They are expected to grow toward km-sized objects called planetesimals. The resulting planetesimals further coalesce by gravity and form planets. However, there are some barriers preventing planetesimal formation, which includes fast radial drift and collisional fragmentation of dust grains. To circumvent the barriers and to explain planetesimal formation, previous studies have proposed hydrodynamic instabilities of dusty-gas disks. The instabilities can cause dust clumping, and planetesimals form if the resulting clumps collapse self-gravitationally. We have been investigating the linear/nonlinear development of these dust-gas instabilities. We also found a new instability driven by collisional growth of dust, which can bridge a potential gap between the first dust growth and the later planetesimal formation via the previous instabilities. In this talk, I will introduce our work on the dust-driven instabilities and their impact on planetesimal formation.

Venue: Hybrid Format (3F #359 and Zoom), Main Research Building

Event Official Language: English

Does horizontal gene transfer stabilize cooperation in bacteria?

January 16 (Tue) at 16:00 - 17:00, 2024

Anna Dewar (Postdoctoral Researcher, Department of Biology, University of Oxford, UK)

Bacteria are highly social. Much of this sociality occurs through the production of cooperative ‘public goods’. Unlike in animals, bacterial genes are able to transfer horizontally between individuals, in addition to vertically via descendants. This widespread horizontal gene transfer has implications for the concept of relatedness and how cooperation is maintained in bacteria. It has been suggested that horizontal gene transfer, particularly via small segments of DNA called plasmids, could stabilize cooperation in bacteria. Transfer of a cooperative gene could turn non-cooperative ‘cheats’ into cooperators, preventing cheats from invading and destabilizing cooperation. We tested this with a comparative analysis across bacterial species. In contrast to the predictions of the hypothesis, we found that genes for cooperative traits were not more likely to be carried on either: (1) plasmids compared to chromosomes; or (2) plasmids that transfer at higher rates. Our results were supported by theoretical modelling which showed that, while horizontal gene transfer can help cooperative genes initially invade a population, it has less influence on the longer-term maintenance of cooperation.

Venue: via Zoom

Event Official Language: English

Probing structure of neutron stars through X-ray bursters

January 12 (Fri) at 14:00 - 15:15, 2024

Akira Dohi (Special Postdoctoral Researcher, Astrophysical Big Bang Laboratory, RIKEN Cluster for Pioneering Research (CPR))

Type-I X-ray bursts are rapidly brightening phenomena triggered by the nuclear burning of light elements near the surface of accreting neutron stars. Most of the X-ray bursters show irregular behavior of light curves. However, some X-ray bursters are somehow quite regular, i.e., constant recurrence time and constant shaper of light curves, and are often called Clocked bursters, which are powerful sites to probe uncertainties of many model parameters such as accretion rate, the composition of accreted matter, reaction rates, neutron star structure, and temperature. In this study, we focus on the uncertainties of the equation of states, which determines the latter two properties. Based on our numerical models covering whole areas of neutron stars, we will present their impact on X-ray burst light curves. Furthermore, we will discuss the possibility of constraining the equation of states from Clocked bursters such as GS 1826-24 and 1RXS J180408.9-342058.

Venue: Seminar Room #359 (Main Venue) / via Zoom

Event Official Language: English

Seoul National University student group visit

January 10 (Wed) at 14:00 - 20:00, 2024

Catherine Beauchemin (Deputy Program Director, iTHEMS)
Akinori Tanaka (Senior Research Scientist, RIKEN Center for Advanced Intelligence Project (AIP))
Misako Tatsuuma (Research Scientist, iTHEMS)
Ryo Namba (Senior Research Scientist, iTHEMS)
Dongwook Ghim (Postdoctoral Researcher, iTHEMS)
Steffen Backes (Senior Research Scientist, iTHEMS)

A group of 22 undergraduate students in the GLEAP programme at Seoul National University will visit iTHEMS to hear short talks by our members, exchange one-on-one, and visit our facilities. I would like to encourage all available iTHEMS members to take part in this event which will be held in different spaces throughout the day, all at the RIKEN Wako campus Main Research Building: 15:50-16:10 at iTHEMS Common Room (#246-248) Coffee break with iTHEMS members and SNU visitors 16:10-17:50 on 4th floor, room #435-437 Short talks by iTHEMS members 18:05-18:30 in 3rd floor common space Short intro talks by SNU visitors 18:30-20:00 in 3rd floor common space Free informal discussion between SNU visitors and iTHEMS members over some light food [Note some slight changes in the times previously announced]

Venue: 3rd floor public space, Main Research Building / #435-437, Main Research Building / Common Room #246-248

Event Official Language: English

Symmetry Topological field theory for Subsystem symmetry

January 9 (Tue) at 15:00 - 16:00, 2024

Qiang Jia (Research Fellow, School of Physics, Korea Institute for Advanced Study (KIAS), Republic of Korea)

We generalize the idea of symmetry topological field theory (SymTFT) to subsystem symmetry. We propose the 2-foliated BF theory with level N in (3+1)d as subsystem SymTFT for subsystem Z_N symmetry in (2+1)d. Focusing on N=2, we investigate various topological boundaries. The subsystem Kramers-Wannier and Jordan-Wigner dualities can be viewed as boundary transformations of the subsystem SymTFT and are included in a larger duality web from the subsystem SL(2,Z_2) symmetry of the bulk foliated BF theory.

Venue: via Zoom / Seminar Room #359

Event Official Language: English

Functional Renormalization Group at Niigata 2024

January 7 (Sun) - 8 (Mon), 2024

Gergely Fejos (Assistant Professor, Institute of Physics, Eötvös Loránd University, Hungary)
Kenji Fukushima (Professor, Department of Physics, Graduate School of Science, The University of Tokyo)
Kouichi Okunishi (Associate Professor, Faculty of Science, Niigata University)
Junichi Haruna (Ph.D. Student, Graduate School of Science, Kyoto University)
Xu-Guang Huang (Professor, Physics Department and Center for Particle Physics and Field Theory, Fudan University, China)
Katsumi Itoh (Professor, Faculty of Education, Niigata University)
Kiyoharu Kawana (Research Fellow, Korea Institute for Advanced Study (KIAS), Republic of Korea)
Shunsuke Yabunaka (Researcher, Japan Atomic Energy Agency (JAEA))
Takeru Yokota (Special Postdoctoral Researcher, iTHEMS)

One of the most fundamental challenges in theoretical physics is to uncover the physical properties of strongly-interacting quantum many-body systems. This problem is shared in both subatomic physics and condensed matter physics; e.g., to unveil ground state structures and dynamical aspects of quantum systems. However, it has been an unresolved issue to establish non-perturbative theoretical tools, which allows a reliable analytic approach to quantum many-body problems described by field theory. The Functional Renormalization Group (FRG) is proposed as one of the theoretical methods that facilitates the non-perturbative investigation of quantum many-body systems. The FRG has found applications in various fields of physics, ranging from particle and nuclear physics to condensed matter physics, leading to several unique achievements in each fields. The aim of this two-day workshop is to provide an overview of the recent applications and progress of FRG in various fields of physics, discuss future directions, and explore potential new collaborations that bridge different fields of physics.

Venue: Kaishi Professional University Yoneyama Campus (Main Venue) / via Zoom

Event Official Language: English