2025年度セミナー Seminars in 2025
今年度後期は、原則として金曜日午後１３時３０分から生産技術研究所（柏キャンパス）研究実験棟Ⅰの３階大会議室で行います。 このセミナーの他にも、毎週月曜日午後１３時３０分から本郷キャンパス理学部１号館２０６号室で統計力学セミナーにも参加しています。
For the first half of this school year, we do regular seminars from 13:30 JST every Thursday at the large conference room on the third floor of the Research and Testing Complex I, Institute of Industrial Science (Building 30 of this map). We also attend the seminar series Statistical Physics seminar series from 13:30 JST every Monday at Room 206, Science Bldg. 1 in the Hongo campus.
| 日程 Date |
時間 Time |
講演者 Speaker |
演題・Abstract Title and Abstract |
| 05月08日(木) Thursday, May 08 |
14:00 |
法橋顕広（Hokkyo Akihiro）さん （東大 / U. Tokyo） |
Rigorous Test for Quantum Integrability and Nonintegrability 要旨 |
| 05月15日(木) Thursday, May 15 |
14:00 |
永山龍那（Nagayama Ryuna）さん （東大 / U. Tokyo） |
Infinite variety of activities and thermodynamic speed limits based on general means 要旨 |
| 05月29日(木) Thursday, May 29 |
14:00 |
石井敬直（Ishii Takanao）さん （東大 / U. Tokyo） |
Quantum i.i.d. steady states in open quantum many-body systems 要旨 |
| 06月05日(木) Thursday, June 05 |
14:00 |
渡邉開人（Watanabe Kaito）さん （東大 / U. Tokyo） |
Universal work extraction in quantum thermodynamics 要旨 |
| 06月12日(木) Thursday, June 12 |
16:00 |
牧口乃大（Makiguchi Norihiro）さん （東大 / U. Tokyo） |
Analysis of Flow- and Vorticity-Induced Currents in Graphene Electron Fluid 要旨 |
| 06月19日(木) Thursday, June 19 |
14:00 |
吉田崇晴（Yoshida Takaharu）さん （東京理科大 / Tokyo U. Sci.） |
Proposal for experimental realization of quantum spin chains with quasiperiodic interaction using Rydberg atoms 要旨 |
| 06月26日(木) Thursday, June 26 |
14:00 |
真弓愛菜（Mayumi Aina）さん （芝浦工大 / Shibaura Inst. of Tech.） |
Commutator-Based Extensions of the Robertson and Schrödinger Uncertainty Relations 要旨 |
| 07月10日(木) Thursday, July 10 |
14:00 |
白井俊也（Shirai Shunya）さん （大阪公立大 / Osaka Metro. U.） |
The dynamics of a particle embedded in a topological environment 要旨 |
| 07月11日(金) Friday, July 11 |
10:30 |
比屋根芳周（Hiyane Hoshu）さん （OIST） |
Emergence of nonequilibrium Lieb excitations in periodically driven strongly interacting bosons 要旨 |
| 07月24日(木) Thursday, July 24 |
14:00 |
西川秀明（Nishikawa Hideaki）さん （京大 / Kyoto U.） |
Energy and spin diffusion in the long-range interacting spin systems 要旨 |
| 10月10日(金) Friday, October 10 |
13:30 |
三橋洋亮（Mitsuhashi Yosuke）さん （理研 / RIKEN） |
Unitary Designs in Symmetric Quantum Random Circuits 要旨 |
| 10月17日(金) Friday, October 17 |
13:30 |
松田諒太（Matsuda Ryota）さん （東大 / U. Tokyo） |
Entanglement negativity in free fermions 要旨 |
| 11月05日(水) Wednesday, November 05 |
16:00 |
インフォーマルセミナー 要旨 | |
| 11月07日(金) Friday, November 07 |
13:30 |
内山智香子（Uchiyama Chikako）さん （山梨大 / U. Yamanashi） |
Quantum Master Equation: Microscopic Derivation and Advanced Extensions 要旨 |
| 11月14日(金) Friday, November 14 |
13:30 |
吉村耕平（Yoshimura Kohei）さん （理研 / RIKEN） |
Quantum extension of a thermodynamic uncertainty relation via the quasiprobability 要旨 |
| 11月21日(金) Friday, November 21 |
13:30 |
森崇人（Mori Takato）さん （立教大 / Rikkyo U.） |
Lesson from a violation of CHSH inequality to holographic principle 要旨 |
| 11月28日(金) Friday, November 28 |
13:30 |
池内耀洋（Ikeuchi Teruhiro）さん （慶應大 / Keio U.） |
Error bounds on the universal Lindblad equation in thermodynamic limit 要旨 |
| 12月19日(金) Friday, December 19 |
13:30 |
Bao Ruicheng さん （東大 / U. Tokyo） |
Initial-State Typicality in Quantum Relaxation with implications for the Mpemba effect and a new performance metric for dissipative quantum tasks 要旨 |
| 12月19日(金) Friday, December 19 |
15:30 |
Raúl Hidalgo-Sacoto さん （OIST） |
Interacting Anyons in One Dimension: zero-range interactions beyond Bose-Fermi statistics 要旨 |
| 12月26日(金) Friday, December 26 |
13:30 |
石山大貴（Ishiyama Taiki）さん （東京科学大 / Institute of Science Tokyo） |
Exact density profile and current fluctuations in a tight-binding chain with dephasing noise 要旨 |
| 01月21日(水) Wednesday, January 21 |
13:30 |
野神亮介（Nogami Ryosuke）さん （名大 / Nagoya U.） |
Observable-dependent quantum realizability of correlations 要旨 |
第０１回
講師：法橋顕広（Hokkyo Akihiro）さん（東大 / U. Tokyo）日時：２０２５年０５月０８日（木）１４時００分〜 / Thursday, 08th May 2025, 14:00 JST -
演題：Rigorous Test for Quantum Integrability and Nonintegrability
要旨：The integrability of a quantum many-body system, which is characterized by the presence or absence of local conserved quantities, drastically impacts the dynamics of isolated systems, including thermalization. Nevertheless, a rigorous and comprehensive method for determining integrability or nonintegrability has remained elusive. In this talk, we address this challenge by introducing rigorously provable tests for integrability and nonintegrability of quantum spin systems with finite-range interactions. Our results significantly simplify existing proofs of nonintegrability, such as those for the S=1/2 Heisenberg chain with nearest-and next-nearest-neighbor interactions, the S=1 bilinear-biquadratic chain and the S=1/2 XYZ model in two or higher dimensions. This work also offers a partial resolution to the long-standing conjecture that integrability is governed by the existence of local conserved quantities with small support. Our framework ensures that the nonintegrability of one-dimensional spin systems with translational symmetry can be verified algorithmically, independently of system size.
第０２回
講師：永山龍那（Nagayama Ryuna）さん（東大 / U. Tokyo）日時：２０２５年０５月１５日（木）１４時００分〜 / Thursday, 15th May 2025, 14:00 JST -
演題：Infinite variety of activities and thermodynamic speed limits based on general means
要旨：Thermodynamic speed limits (TSLs) represent a fundamental constraint that faster state changes require greater dissipation. In TSLs for Markov jump processes, the kinetic activity is essential to relate dissipation to the speed of time evolution. The kinetic activity is measured in several ways: One common way is to use the arithmetic mean of the forward and backward fluxes, which gives the dynamical activity. Instead of the arithmetic mean, we can also use the logarithmic mean, which provides the dynamical state mobility [1]. While not directly used in TSLs, other means are also used in nonequilibrium thermodynamics [2]. For instance, the geometric mean of the bidirectional fluxes appears in the macroscopic fluctuation theory to describe the fluctuations of empirical quantities. However, whether TSLs can be derived with arbitrary means remains an open question.
We address this question by generalizing activity and deriving TSLs based on a general class of means [3]. We identify the mathematical conditions under which such means yield TSLs and reveal that various means, including the Stolarsky mean, satisfy these conditions. Since the Stolarsky mean includes an infinite variety of means, such as the harmonic, geometric, logarithmic, and arithmetic means, we can derive infinitely many TSLs. We show that the lower bounds on dissipation in these TSLs correspond to the minimum dissipation achievable under conservative forces. This framework unifies existing results based on the dynamical activity [4] and the dynamical state mobility [1], providing a comprehensive perspective on TSLs. We also discuss the hierarchy of TSLs, the application to deterministic chemical systems, and the comparison with excess entropy production.
[1] T. V. Vu and K. Saito, Phys. Rev. X 13(1), 011013 (2023).
[2] M. A. Peletier et al., Calc. Var. Partial Differ. Equ. 61, 1-85 (2022).
[3] R. Nagayama, K. Yoshimura, and S. Ito, Phys. Rev. Res. 7(1), 013307 (2025).
[4] A. Dechant, J. Phys. A 55(9), 094001 (2022).
第０３回
講師：石井敬直（Ishii Takanao）さん（東大 / U. Tokyo）日時：２０２５年０５月２９日（木）１４時００分〜 / Thursday, 29th May 2025, 14:00 JST -
演題：Quantum i.i.d. steady states in open quantum many-body systems
要旨：Quantum entanglement and spatial correlations serve as powerful probes of phase transitions in closed quantum systems and are expected to play an equally pivotal role in characterizing phase transitions in open quantum systems, particularly in the context of dissipative phase transitions [1, 2]. Since dissipative phase transitions manifest themselves as a dramatic change of steady states as a function of external parameters, investigating quantum entanglement and spatial correlations of steady states is a crucial step toward understanding such phase transitions. However, the conditions for quantum entanglement and spatial correlations to vanish in the steady state of an open quantum many-body system governed by the GKSL dynamics are yet to be established.
As an initial step toward resolving the aforementioned problem, we obtain a set of equivalent conditions for the steady state to be a quantum independent and identically distributed (i.i.d.) state, which is a subclass of separable states (no quantum entanglement) or tensor product states (no spatial correlations) [3]. The obtained conditions can be applied universally, including spin, fermionic, and bosonic systems, enabling us to judge whether a system has a quantum i.i.d. steady state or not, simply from the local terms involved in the Lindbladian. We also discuss an equivalent condition that the state retains the quantum i.i.d. form throughout the time evolution. Systems satisfying these conditions offer significant analytical tractability, enabling the computation of dynamical properties such as time-correlation functions and response functions.
[1] J. Hannukainen and J. Larson, Phys. Rev. A 98, 4 (2018).
[2] Q. Wang and S. F. Yelin, arXiv preprint arXiv:2308.13627 (2023).
[3] in preparation
第０４回
講師：渡邉開人（Watanabe kaito）さん（東大 / U. Tokyo）日時：２０２５年０６月０５日（木）１４時００分〜 / Thursday, 05th June 2025, 14:00 JST -
演題：Universal work extraction in quantum thermodynamics
要旨：Evaluating the maximum amount of work extractable from a nanoscale quantum system is one of the central problems in quantum thermodynamics. Previous works identified the free energy of the input state as the optimal rate of extractable work under the crucial assumption: experimenters know the description of the given quantum state, which restricts the applicability to significantly limited settings. Here, we show that this optimal extractable work can be achieved without knowing the input states at all, removing the aforementioned fundamental operational restrictions. We achieve this by presenting a universal work extraction protocol, whose description does not depend on input states but nevertheless extracts work quantified by the free energy of the unknown input state. Remarkably, our result partially encompasses the case of infinite-dimensional systems, for which optimal extractable work has not been known even for the standard state-aware setting. Our results clarify that, in spite of the crucial difference between the state-aware and state-agnostic scenarios in accomplishing information-theoretic tasks, whether we are in possession of information on the given state does not influence the optimal performance of the asymptotic work extraction.
第０５回
講師：牧口乃大（Makiguchi Norihiro）さん（東大 / U. Tokyo）日時：２０２５年０６月１２日（木）１６時００分〜 / Thursday, 12th June 2025, 16:00 JST -
演題：Analysis of Flow- and Vorticity-Induced Currents in Graphene Electron Fluid
要旨：In graphene, electron–electron scattering dominates within a specific temperature window (roughly 100–200 K), so the charge carriers behave collectively as an electron fluid [1]. In this regime, we determine the conductivity that links flow fields and local vorticity to the electric currents they generate, using linear-response theory. A central insight is that a perturbation of the flow can be recast as a perturbation of a background gravitational field [2]. Consequently, the relevant transport coefficients are obtained via the Kubo formula from the correlation function between the electric-current operator and the energy–momentum tensor. The resulting conductivity systematically incorporates viscous effects and furnishes a theoretical foundation for understanding current-generation mechanisms driven by vorticity in graphene electron fluids.
[1] J. A. Sulpizio, L. Ella et al, Visualizing Poiseuille flow of hydrodynamic electrons, Nature vol. 576, pages 75-79 (2019).
[2] S. Y. F. Liu and Y. Yin, Spin polarization induced by the hydrodynamic gradients, J. High Energy Phys. 07 (2021) 188.
第０６回
講師：吉田崇晴（Yoshida Takaharu）さん（東京理科大 / Tokyo U. Sci.）日時：２０２５年０６月１９日（木）１４時００分〜 / Thursday, 19th June 2025, 14:00 JST -
演題：Proposal for experimental realization of quantum spin chains with quasiperiodic interaction using Rydberg atoms
要旨：Investigating the localization properties of interacting disordered systems plays a crucial role in understanding the fundamental origins of both the emergence and the breakdown of statistical mechanics in closed quantum systems. However, simulating such systems on classical computers is challenging due to their complexity. On the other hand, recent advances in experimental technology have made it possible to realize closed quantum systems with high controllability. In particular, Rydberg atoms [1] are an emerging platform for quantum simulation, as they offer the advantage of individual control over the spatial positions of atoms and the ability to tune their interactions.
In this talk, I will talk about my recent work proposing an experimental method to realize S=1/2 and S=1 quantum spin models with quasiperiodic interactions using Rydberg atoms [2]. I will also present numerical results for these models, confirming that they exhibit a many-body critical (MBC) regime [3], a newly reported localization phenomenon distinct from both ergodic and many-body localized phases.
[1] A. Browaeys, D. Barredo, and T. Lahaye, J. Phys. B At. Mol. Opt. Phys. 49, 152001 (2016).
[2] T. Yoshida, M. Kunimi, and T. Nikuni, arXiv:2409.08497 (2024).
[3] Y. Wang, C. Cheng, X.-J. Liu, and D. Yu, Phys. Rev. Lett. 126, 080602 (2021).
第０７回
講師：真弓愛菜（Mayumi Aina）さん（芝浦工大 / Shibaura Inst. of Tech.）日時：２０２５年０６月２６日（木）１４時００分〜 / Thursday, 26th June 2025, 14:00 JST -
演題：Commutator-Based Extensions of the Robertson and Schrödinger Uncertainty Relations
要旨：We present two distinct improvements to the celebrated Robertson and Schrödinger preparation uncertainty relations by revealing previously overlooked contributions to their lower bounds. Our new terms are directly dictated by the commutator of the observables concerned, the fact of which signals their purely quantum origin. Interestingly, the new terms explicitly reflect the spectral structure of the density operator, which tend to become more significant as the quantum state becomes more mixed for finite-dimensional systems. For two-level systems, our extension of the Schrödinger relation universally attains the equality, thereby providing a complete characterization of the trade-off relation.
[1] A. Mayumi, G. Kimura, H. Ohno, and D. Chruściński, Phys. Rev. A 110, 062215 (2024).
[2] G. Kimura, A. Mayumi, H. Ohno, J. Lee, and D. Chruściński, arXiv:2504.20404 (2025).
[3] G. Kimura, A. Mayumi, and H. Yamashita, arXiv:2505.19861 (2025).
第０８回
講師：白井俊也（Shirai Shunya）さん（大阪公立大 / Osaka Metro. U.）日時：２０２５年０７月１０日（木）１４時００分〜 / Thursday, 10th July 2025, 14:00 JST -
演題：The dynamics of a particle embedded in a topological environment
要旨：In the most well-known dynamical process in open quantum systems, the particle decays exponentially and is irreversibly transferred to the environment. This process can be described by the so-called "resonance state" and its complex eigenvalue. However, this picture can be modified in numerous ways when one changes the properties of the environment into which the system decays. For example, strong coupling to the environment can induce an atom-photon bound state, such that the particle cannot decay completely from the original system ("fractional decay").
We consider a system which a quantum emitter decays into an infinite extension of the Su-Schrieffer-Heeger (SSH) chain with alternating nearest-neighbor couplings J_1 and J_2. This system behaves analogously to a one-dimensional topological insulator from condensed matter physics. Curiously, we discovered a surface-like zero-energy state in the SSH chain that strongly influences the dynamics of the quantum emitter, despite being entirely decoupled from it (seemingly like an "atom-photon bound state" - but without any contribution from the "atom"). Further, we found that when the quantum emitter coupling g corresponds to g=√(J_1^2 - J_2^2), an exceptional point occurs at which two other in-gap states coalesce with the zero-energy state to form a peculiar state that extends in only one direction. Now, we try to investigate that how this peculiar state affects the dynamics of a particle.
[1] N. Hatano, K. Sasada, H. Nakamura, and T. Petrosky, Prog. Theor. Phys. 119, 187 (2008).
[2] S. Garmon, T. Petrosky, L. Simine, and D. Segal, Fortschr. Phys. 61, 261 (2013).
[3] S. Garmon, G. Ordonez, N. Hatano, Phys. Rev. Res. 3, 033029 (2021).
第０９回
講師：比屋根芳周（Hiyane Hoshu）さん（OIST）日時：２０２５年０７月１１日（金）１０時３０分〜 / Friday, 11th July 2025, 10:30 JST -
演題：Emergence of nonequilibrium Lieb excitations in periodically driven strongly interacting bosons
要旨：We study the exact time-averaged spectral function of a gas of strongly correlated Tonks-Girardeau bosons subjected to a strong periodic drive. Utilizing the theory of Floquet spectral function in conjunction with the Bose-Fermi mapping theorem, we show that nonequilibrium Lieb modes emerge if the underlying mapped fermions form a Floquet-Fermi sea.
The analysis presented here can be used to determine the spectral properties of more general bosonic systems, such as Bose-condensed gas or Lieb-Liniger gas, providing a powerful tool to study the many-body properties of the Floquet-engineered bosonic systems.
第１０回
講師：西川秀明（Nishikawa Hideaki）さん（京大 / Kyoto U.）日時：２０２５年０７月２４日（木）１４時００分〜 / Thursday, 24th July 2025, 14:00 JST -
演題：Energy and spin diffusion in the long-range interacting spin systems
要旨：We investigate the energy and spin diffusion in the extensive long-range interacting spin systems.
First, we study energy diffusion in long-range interacting spin systems, where the interaction decays algebraically as $V(r) \propto r^{-\alpha}$ with the distance $r$ between the sites. We consider prototypical spin systems, the transverse Ising model, and the XYZ model in the $D$-dimensional lattice with a finite exponent $\alpha >D$ which guarantees the thermodynamic extensivity.
In one dimension, both normal and anomalous diffusion are observed, where the anomalous diffusion is attributed to anomalous enhancement of the amplitude of the equilibrium current correlation. We prove the power-law clustering property of arbitrary orders of joint cumulants in general dimensions. Applying this theorem to equal-time current correlations, we further prove several theorems leading to the statement that the sufficient condition for normal diffusion in one dimension is $\alpha > 3/2$ regardless of the models. The fluctuating hydrodynamics approach consistently explains L'{e}vy diffusion for $\alpha < 3/2$, which implies the condition is optimal. In higher dimensions of $D \geq 2$, normal diffusion is indicated as long as $\alpha > D$ [1].
Next, we also investigate spin diffusion in long-range interacting XXZ model, with a power-law exponent $\alpha>D$. We obtain the same scaling behavior for spin diffusion, both in one dimension and higher dimensions [2].
We expect this theoretical framework is broadly applicable to the transport phenomena in a wide class of long-range interacting systems.
[1] HN and K.Saito, arXiv:2502.10139.
[2] HN and K.Saito, in preparation.
第１１回
講師：三橋洋亮（Mitsuhashi Yosuke）さん（理研 / RIKEN）日時：２０２５年１０月１０日（金）１３時３０分〜 / Friday, 10th October 2025, 13:30 JST -
演題：Unitary Designs in Symmetric Quantum Random Circuits
要旨：What emerges from the interplay of two fundamental notions in physics, symmetry and randomness? Symmetry is central to understanding phases of matter and useful for designing efficient algorithms. Randomness, on the other hand, appears in many topics such as quantum information processing, quantum chaos, and thermalization. However, generating truly random unitaries, i.e., sampling from the uniform distribution over the unitary group, is prohibitively hard. To address this, unitary t-designs are employed, which are distributions that reproduce the uniform distribution up to the t-th moment. For example, the Clifford group forms a unitary 3-design [1], and local random circuits asymptotically form unitary t-designs for all t [2].
This naturally leads to the following question: Do symmetry-constrained versions of these distributions form unitary designs over the symmetric unitary subgroup up to the same order? We address this question in the following two cases.
First, we consider subgroups of the Clifford group that respect a given symmetry. In Ref. [3], we prove that such symmetric Clifford groups form unitary 3-designs if and only if the symmetry constraint can be expressed as commutation with some Pauli subgroup. Moreover, we present an explicit procedure for uniformly sampling symmetric Clifford gates using only 2-qubit gates, making the scheme implementable in realistic setups.
Next, we study symmetric local random circuits on qudit systems, which are composed of random unitaries acting on randomly selected k qudits for some given k. In Ref. [4], we show that symmetry induces a fundamental upper bound on the achievable design order, and the tight upper bound is formulated as a simple integer optimization problem. By solving the optimization problem, we explicitly obtain the tight upper bound for three physically relevant symmetry groups, Z_2, U(1), and SU(2).
[1] H. Zhu, Multiqubit Clifford groups are unitary 3-designs, Phys. Rev. A 96, 062336 (2017).
[2] F. G. L. S. Brandao, A. W. Harrow, and M. Horodecki, Local random quantum circuits are approximate polynomial-designs, Commun. Math. Phys. 346, 397 (2016).
[3] Y. Mitsuhashi and N. Yoshioka, Clifford Group and Unitary Designs under Symmetry, PRX Quantum 4, 040331 (2023).
[4] Y. Mitsuhashi, R. Suzuki, T. Soejima, and N. Yoshioka, Unitary Designs of Symmetric Local Random Circuits, Phys. Rev. Lett. 134, 180404 (2025).
第１２回
講師：松田諒太（Matsuda Ryota）さん（東大 / U. Tokyo）日時：２０２５年１０月１７日（金）１３時３０分〜 / Friday, 17th October 2025, 13:30 JST -
演題：Entanglement negativity in free fermions
要旨：Entanglement negativity is a widely used entanglement measure in mixed states due to its computability. However, extending its definition to fermionic systems is highly nontrivial, and its general properties remain largely unexplored even for free fermions. In this seminar, we first review the proposal of fermionic entanglement negativity in Ref. [1] and present an explicit formula in free fermions. Based on this formula, we discuss its universal properties in both static and dynamical settings. For both cases, we derive universal bounds in terms of the covariance matrix and apply them to prove an entanglement area law for systems with locality. This talk is based on our recent work [2].
[1] H. Shapourian, K. Shiozaki, and S. Ryu, Phys. Rev. B 95, 165101 (2017).
[2] R. Matsuda and Z. Gong, arXiv:2507.20947 (2025).
第１３回
講師：日時：２０２５年１１月０５日（水）１６時００分〜 / Wednesday, 05th November 2025, 16:00 JST -
演題：インフォーマルセミナー
第１４回
講師：内山智香子（Uchiyama Chikako）さん（山梨大 / U. Yamanashi）日時：２０２５年１１月０７日（金）１３時３０分〜 / Friday, 07th November 2025, 13:30 JST -
演題：Quantum Master Equation: Microscopic Derivation and Advanced Extensions
要旨：The quantum master equation is a fundamental framework for understanding open quantum systems. In this presentation, I will provide a comprehensive review of the microscopic derivation of the quantum master equation and discuss its important extensions, which include full counting statistics, the Heisenberg picture, and complex susceptibility in cases where there are initial correlations between the system and its environment. Join me as we explore these key concepts that enhance our understanding of quantum dynamics and lay the groundwork for future advancements in the field.
第１５回
講師：吉村耕平（Yoshimura Kohei）さん（理研 / RIKEN）日時：２０２５年１１月１４日（金）１３時３０分〜 / Friday, 14th November 2025, 13:30 JST -
演題：Quantum extension of a thermodynamic uncertainty relation via the quasiprobability
要旨：Extending thermodynamic trade-offs to the quantum regime is a fundamental step toward understanding nonequilibrium behavior in quantum systems. In this talk, I show that the thermodynamic uncertainty relation in the short-time limit can be generalized to the quantum regime by using a quasiprobability, a quantum analogue of the joint probability in classical stochastic systems. I begin with a brief review of stochastic and quantum thermodynamics, and explain why quasiprobabilities are necessary (briefly, it is because thermodynamic uncertainty relations involve dynamical fluctuations). Then I present the main inequality and its detailed derivation. Further, I will demonstrate that the non-classicality of the quasiprobability can lead to an improvement of a quality measure.
第１６回
講師：森崇人（Mori Takato）さん（立教大 / Rikkyo U.）日時：２０２５年１１月２１日（金）１３時３０分〜 / Friday, 21th November 2025, 13:30 JST -
演題：Lesson from a violation of CHSH inequality to holographic principle
要旨：Holographic principle is a prominent appraoch to quantum gravity (QG), which is yet to be formulated. It is a duality between d-dimensional QG states in a bulk and (d-1)-dimensional quantum states on the boundary of the bulk. In the AdS/CFT correspondence, an example of holography, the quantum theory on the boundary of AdS is well-understood as conformal field theory. Thus, this duality enables us to understand QG, something we do not know well, from something familiar to us.
Nevertheless, it is far from straightforward to apply AdS/CFT to our universe as our universe (like dS) is different from AdS. To overcome this, dS/CFT, which is an analytic continuation of AdS/CFT, has been proposed 24 years ago. However, so far there is no proper justifcation for the analytic continuation and many works just assume dS/CFT. In this talk, I will talk about my on-going work on testing the validity of dS/CFT by checking the Tsirelson bound of the CHSH observable. I will discuss difficulty associated with infinite dimensions, how one will overcome it, violations in (A)dS/CFT, and subtleties in their interpretations.
第１７回
講師：池内耀洋（Ikeuchi Teruhiro）さん（慶應大 / Keio U.）日時：２０２５年１１月２８日（金）１３時３０分〜 / Friday, 28th November 2025, 13:30 JST -
演題：Error bounds on the universal Lindblad equation in thermodynamic limit
要旨：Open quantum many-body systems have attracted much attention recently. Quantum control using dissipation and noisy quantum computing are examples of such systems. Although the Lindblad equation is widely used to describe Markovian dynamics of open quantum systems, its microscopic derivation has not been established yet. Therefore, many derivations of the Lindblad equation have been proposed so far. Universal Lindblad Equation (ULE) is superior among them since ULE is applicable to many-body systems. However, there has been a problem that the accumulation of errors had not been analytically evaluated when ULE was applied to many-body systems. In our research, we analytically evaluated the accumulation of errors in thermodynamic limit and obtained a finite error independent of both time and system size.
In this talk, I will start with the basic concepts of open quantum systems and introduce studies on the derivation of the Lindblad equation including our result.
[1] T. Ikeuchi and T. Mori, Phys. Rev. B 112, 094309 (2025)
第１８回
講師：Bao Ruicheng さん（東大 / U. Tokyo）日時：２０２５年１２月１９日（金）１３時３０分〜 / Friday, 19th December 2025, 13:30 JST -
演題：Initial-State Typicality in Quantum Relaxation with implications for the Mpemba effect and a new performance metric for dissipative quantum tasks
要旨：Relaxation in open quantum systems is fundamental to quantum science and technologies. However, the systematic influence of the initial state on relaxation dynamics remains a central, largely open question. Here, we reveal a typicality phenomenon in high-dimensional open quantum systems: under verifiable conditions, the relaxation process becomes nearly initial-state-independent as system size increases. We rigorously establish this typicality for broad classes of thermalization processes. This finding has significant conceptual implications. It suggests that widely used metrics, such as the Liouvillian gap and conventional relaxation time, merit re-examination in this typical regime. We formalize this by introducing two new concepts: the "typical strong Mpemba effect" and the "typical relaxation time." Practically, we identify a scalable route to accelerating relaxation and propose a typical-case benchmark for dissipative quantum tasks. The new benchmark complements conventional worst-case metrics, offering a more relevant descriptor for the cost of thermal quantum simulations and dissipative state preparation.
第１９回
講師：Raúl Hidalgo-Sacoto さん（OIST）日時：２０２５年１２月１９日（金）１５時３０分〜 / Friday, 19th December 2025, 15:30 JST -
演題：Interacting Anyons in One Dimension: zero-range interactions beyond Bose-Fermi statistics
要旨：Non-relativistic anyons in 1D possess generalized exchange statistics in which the exchange of two identical anyons generates a non-local phase that is governed by the spatial ordering of the particles and the statistical parameter . Working in the continuum, I will discuss the existence of two distinct types of 1D anyons, namely bosonic anyons and fermionic anyons. Later I will introduce a many-body Hamiltonian with additive two-body zero-range interactions that supports bosonic and fermionic anyon eigenstates, which are, for arbitrary interaction strength, related through a generalized bosonic-anyon--fermionic-anyon mapping, an extension of the celebrated Bose-Fermi mapping for zero-range interacting 1D systems. The momentum distributions of bosonic and fermionic anyons are distinct: while both feature and tails, the associated prefactors differ. Our work reveals intricate connections between the generalized exchange statistics, the universal two- and three-body Tan contacts of systems consisting of identical particles, and the emergence of statistics-induced chiral symmetry breaking. I will discuss about possible experimental realization with spin-orbit coupling of two distinguishable bosons.
第２１回
講師：野神亮介（Nogami Ryosuke）さん（名大 / Nagoya U.）日時：２０２６年０１月２１日（水）１３時３０分〜 / Wednesday, 21st January 2025, 13:30 JST -
演題：Observable-dependent quantum realizability of correlations
要旨：We derive a necessary and sufficient condition for quantum realizability of correlations in the Clauser–Horne–Shimony–Holt setup in an observable-dependent setting, where the observables are fixed in advance. This result addresses a fundamental question common to both local realism and quantum mechanics: under what conditions can a given set of observed data be reproduced in a physical model? Our main result provides an explicit inequality that imposes stronger constraints than previously known observable-independent bounds. Moreover, we apply our result to Bell’s original scenario, revealing that whether Bell’s original inequality is violated depends sensitively on the choice of observables. These findings demonstrate that non-reality in quantum mechanics does not manifest equally in all measurement configurations.