OCTOBER 25-29, 2021, JST ONLINE CONFERENCEABOUT THE 1ST INTERNATIONAL SYMPOSIUM ON
TRANS-SCALE QUANTUM SCIENCE (TSQS2021)

TSQS2021 is a part of the Trans-Scale Quantum Science Institute’s
activities to bring together world-leading scientists from various
branches of physics, and to create opportunities for interdisciplinary
discussions on recent discoveries and possible future developments.
We hope to provide all participants with a holistic perpective of thepresent and future of quantum science, and each lecture will cover its
respective topic from its fundamentals to the most recent advances.
To finish every session, we plan a panel discussion session where we
expect lively interactions between the audience and the speakers,
who will discuss interdisciplinary topics of interest with specialists
and non-specialists alike. We sincerely hope that students, people
from the industry and academics will benefit from this symposium,
and we are looking forward to everyone’s active participation.

We wish to extend our thanks to all participants, and to JSR
Corporation for sponsoring this event.

Organizing committee
TSQS2021
Trans-Scale Quantum Science Institute
The University of TokyoINVITED SPEAKERS

James G. Analytis

N. Peter Armitage

University of California Berkeley, USA

Johns Hopkins University, USA

Immanuel BlochCollin Broholm

Ludwig Maximilian University of Munich,Germany

Johns Hopkins University, USA

Andrea Cavalleri

Kohei ItohMax Planck Institute, Germany

Dmitri Kharzeev

Keio University, Japan

Debbie Leung

Stony Brook University, USA

University of Waterloo, Canada

Allan MacDonald

Hitoshi Murayama

The University of Texas at Austin, USA

Kae Nemoto

University of California, Berkeley, USA

Hidetoshi Nishimori

National Institute of Informatics, JapanTokyo Institute of Technology, Japan

Hirosi Ooguri

Shinsei Ryu

Kavli IPMU, The University of Tokyo, Japan &California Institute of Technology, USA

Princeton University, USA

Subir Sachdev

Eiji Saitoh

Harvard University, USA

The University of Tokyo, Japan

Hidenori Takagi

Yoshinori Tokura

Max Planck Institute, Germany &The University of Tokyo, JapanRIKEN & The University of Tokyo, Japan

Masahito Ueda

Ashvin Vishwanath

The University of Tokyo, Japan

Jun'ichi Yokoyama
The University of Tokyo, Japan

Harvard University, USA

INSTRUCTIONS FOR AUDIENCE• Please make sure that your audio is set to “Mute”, and your video feed is off when you join
the Conference Zoom.
• Please set “First_name Last_name (Affiliation)” as your Zoom screen name. Example: Taro
Yamada (The University of Tokyo).
• The allotted time for each presentation is 40 minutes, followed by 10 minutes of discussion.
• The allotted time for panel discussions is of 30 minutes for two-speaker panels, and 45
minutes for three-speaker panels.
• Please do not record still frames, video, or sound of the talks and presentations to respect
authorship rights.
• Presentation videos and slides will be available after the symposium at the homepage until
November 15, 2021.
• To pose a question during discussion times, please first use the “raise hand” feature on Zoom.
When prompted by the session chair, please switch on your audio and video. After stating
your question, please again switch off your audio and video feed. Alternatively, you may
type your question in the chat. Then, the session chair will read it out loud.
• A meeting host may remotely mute or switch off the video feed of participants.

INSTRUCTIONS FOR SPEAKERS• Please make sure that your audio is set to “Mute”, and your video feed is off when you join
the Conference Zoom.
• Please set “First_name Last_name (Affiliation)” as your Zoom screen name. Example: Taro
Yamada (The University of Tokyo).
• Please join the Zoom meeting at least 20 minutes before the start of your session to checkthe connection status. The Zoom meeting will be open one hour before the session begins.
• The allotted time for each presentation is 40 minutes, followed by 10 minutes of discussion.
A timer will be displayed on the video screen of the technical moderator.
• The allotted time for panel discussions is of 30 minutes for two-speaker panels, and 45
minutes for three-speaker panels.
• At the start of your presentation or panel discussion, please make sure to switch on the audio
and video feeds and show the presentation slides via the screen share function.
• After the discussion or panel is over, please promptly end the screen-sharing and switch off
your audio and video feed again.

INSTRUCTIONS FOR SESSION CHAIRS• Please make sure that your audio is set to “Mute”, and your video feed is off when you join
the Conference Zoom.
• Please use “Chair: First_name Last_name (Affiliation)” as your Zoom screen name. Example
Chair: Taro Yamada (The University of Tokyo).
• Please join the Zoom meeting at least 20 minutes before the start of your session to checkthe connection status. The Zoom meeting will be open one hour before the session begins.
• The technical moderator of the session will host the Zoom meeting. You will be assigned as aco-host during the session.
• When the session begins, please switch on your audio and video feeds.
• The allotted time for each presentation is 40 minutes, followed by 10 minutes of discussion.
A timer will be displayed on the video screen of the technical moderator.
• The allotted time for panel discussions is of 30 minutes for two-speaker panels, and 45
minutes for three-speaker panels.
• At the beginning of a presentation, please set your audio feed to “Mute”.
• When a presentation is finished, please switch on your audio feed, and proceed withthe discussion following the presentation. If an attendee has raised their hand (by Zoom
gestures), prompt them by name to state their question. Questions might be written in thechat. In this case, please read out loud the question.

PROGRAM (all times JST)Day 1

08:00-08:15

Opening Remarks
Satoru Nakatsuji (U. Tokyo, Japan)

SESSION 1

Chair: Masaki Oshikawa (U. Tokyo, Japan)

08:15-09:05

TBD
Hitoshi Murayama (UC Berkley, USA)

09:05-09:55

Entanglement dynamics of quantum many-bodysystems: quasi-particle v.s. membrane pictures		
Shinsei Ryu (Princeton U., USA)

09:55-10:45

Completeness of gauge charges in quantum gravity
Hirosi Ooguri (Kavli IPMU, U. Tokyo, Japan & Caltech,USA)

10:45-11:30

Panel Discussion

Mon, Oct 25, 2021
08:00-13:50 (JST)SESSION 2

11:40-12:30

Spintronics in magnetic topological insulators
Allan MacDonald (UT Austin, USA)12:30-13:20

Quasi particles and coherence in nano systems		
Eiji Saitoh (U. Tokyo, Japan)

13:20-13:50

Panel Discussion

SESSION 3

Day 2

Kitaev interactions in Co based quantum magnets
N. Peter Armitage (Johns Hopkins U., USA)

08:50-09:40

Low-power, long-range spin transfer in frustrated
magnets and other correlated systems
James G. Analytis (UC Berkeley, USA)

09:40-10:30

Chirality and quantum information
Dmitri Kharzeev (Stony Brook U., USA)

10:30-11:15

Panel Discussion

SESSION 4

Wed, Oct 27, 2021
15:00-19:30 (JST)

Chair: Masao Ogata (U. Tokyo, Japan)

08:00-08:50

Tue, Oct 26, 2021
08:00-11:15 (JST)Day 3

Chair: Masamitsu Hayashi (U. Tokyo, Japan)

Chair: Kensuke Kobayashi (U. Tokyo, Japan)

15:00-15:50

Probing quantum matter in- and out-of equilibrium on alarge-scale atomic quantum simulator
Immanuel Bloch (LMU Munich, Germany)

15:50-16:40

Beyond-Hermitian quantum physics
Masahito Ueda (U. Tokyo, Japan)

16:40-17:10

Panel Discussion

SESSION 5

Chair: Ryusuke Matsunaga (U. Tokyo, Japan)

17:20-18:10

Driven quantum materials			
Andrea Cavalleri (MPI Hamburg, Germany)

18:10-19:00

Quantum spin liquid with fractionalized excitationsmake it real!
Hidenori Takagi (MPI Stuttgart, Germany & U. Tokyo,
Japan)

19:00-19:30

Panel Discussion

PROGRAM (all times JST)SESSION 6

Day 4Thu, Oct 28, 2021
08:00-12:30 (JST)

08:00-08:50

Quantum computing algorithms and software
Kohei Itoh (Keio U., Japan)

08:50-09:40

Quantum channel capacities		
Debbie Leung (U. Waterloo, Canada)

09:40-10:10

Panel Discussion

SESSION 7

Fri, Oct 29, 2021
08:00-13:40 (JST)

Chair: Mio Murao (U. Tokyo, Japan)

10:20-11:10

Quantum simulation by quantum annealing
Hidetoshi Nishimori (TIT, Japan)

11:10-12:00

Quantum computer designs from today’s NISQ processors
to tomorrow’s fault-tolerant quantum computers
Kae Nemoto (NII, Japan)

12:00-12:30

Panel Discussion

SESSION 8

Day 5

Chair: Chair: Mio Murao (U. Tokyo, Japan)

Chair: Satoru Nakatsuji (U. Tokyo, Japan)

08:00-08:50

Emergent electromagnetic responses from topologicalmagnets
Yoshinori Tokura (RIKEN & U. Tokyo, Japan)

08:50-09:40

Emergent quasi-particles in frustrated magnets
Collin Broholm (Johns Hopkins U., USA)

09:40-10:10

Panel Discussion

SESSION 9

Chair: Kenji Fukushima (U. Tokyo, Japan)

10:20-11:10

A simple model of many-particle entanglement: how it
describes black holes and superconductors
Subir Sachdev (Harvard U., USA)

11:10-12:00

Quantum aspects of inflationary cosmology
Jun'ichi Yokoyama (U. Tokyo, Japan)

12:00-12:50

Correlations and topology in twisted structures
Ashvin Vishwanath (Harvard U., USA)12:50-13:35

Panel Discussion

13:35-13:40

Closing Remarks
Masahito Ueda (U. Tokyo, Japan)

Day 1
08:15-09:05

Monday, October 25, 2021

Opening Remarks
Satoru Nakatsuji (U. Tokyo, Japan)

SESSION 1

08:15-09:05

Chair: Masaki Oshikawa (U. Tokyo, Japan)

TBD
Hitoshi Murayama (UC Berkley, USA)

09:05-09:55

Entanglement dynamics of quantum many-bodysystems: quasi-particle v.s. membrane pictures
Shinsei Ryu (Princeton U., USA)

09:55-10:45

Completeness of gauge charges in quantum
gravity
Hirosi Ooguri (Kavli IPMU, U. Tokyo, Japan & Caltech, USA)10:45-11:30

SESSION 2

11:40-12:30

Panel Discussion

Chair: Masamitsu Hayashi (U. Tokyo, Japan)

Spintronics in magnetic topological insulators
Allan MacDonald (UT Austin, USA)12:30-13:20

Quasi particles and coherence in nano systems
Eiji Saitoh (U. Tokyo, Japan)

13:20-13:50

Panel Discussion

SESSION 1 | 08:15-09:05

Day 1
MondayOct 25, 2021

Supersymmetry as a tool to study
quantum systems
Hitoshi Murayama
University of California, Berkeley, LBNL, USA &Kavli IPMU, The University of Tokyo, Japan

Supersymmetry is a symmetry in quantum field theory that can interchange bosons
and fermions. It provides powerful control over the dynamics of strongly correlated
systems which in some cases allows for exact solutions. To approach realistic systems,
however, supersymmetry needs to be broken. I discuss how supersymmetry can be
broken in a specific way to preserve the exact solutions [1]. I use non-abelian gauge
theories as an example of application of this method, to understand properties such asconfinement and chiral symmetry breaking [2].
[1]
1] H.

ayama, Phys. Rev. Lett. 126 25, 251601 (2021)[2]2] C. Csáki et al https://arXiv.org/abs/2106.10288

SESSION 1 | 09:05-09:55

Entanglement dynamics of quantum
many-body systems: quasi-particle v.s.
membrane pictures
Shinsei Ryu
Princeton University, USA

Quantum many-body systems can exhibit rich and complex dynamical behaviors.
Loosely speaking, we can distinguish at least two types of dynamics. Integrable
systems retain the information of initial states during time-evolution. On the other
hand, non-integrable or “chaotic” systems completely forget initial states – they
thermalize at late times. In this talk, we explore different types of quantum dynamics
by looking at how quantum information and quantum entanglement propagate. In
particular, we try to classify different entanglement dynamics by different effective
descriptions, the quasi-particle and membrane pictures. Specifically, we discuss how
the scaling behaviors of various entanglement measures (entanglement entropy,
mutual information, and reflected entropy, etc.) detect integrable or chaotic dynamics
and how they can be captured by the effective descriptions.

SESSION 1 | 09:55-10:45

Completeness of gauge charges inquantum gravity
Hirosi Ooguri
Kavli IPMU, The University of Tokyo, Japan &California Institute of Technology, USA

After reviewing my earlier proofs of the absence of global symmetries and thecompleteness hypothesis in consistent quantum theory in the context of the AdS/CFT
correspondence, I present a derivation of a simple formula for the density of black holemicrostates which transform in each irreducible representation of any finite gauge
group. Since each representation appears with nonzero density, this gives a new proofof the completeness hypothesis for finite group gauge symmetries. Inspired by thegenerality of the argument we further propose that the formula applies at high energy
in any quantum field theory with a finite-group global symmetry, and give someevidence for this conjecture.

SESSION 1 | 11:40-12:30

Spintronics in magnetic topologicalinsulators
Allan MacDonald
The University of Texas at Austin, USA

Spintronics is the study of the interplay between electrical transport properties andmagnetic properties in magnetically ordered conductors – both magnetic configuration
control of electrical properties and electrical control of magnetic properties – and has
applications in magnetic information storage technology. I will discuss the propertiesof magnetic topological insulators like MnBi₂Te₄, and their potential role in future
spintronics. Most of my discussion will be framed in terms of a simplified coupled
Dirac-cone model [1] that captures many qualitative features in a remarkably simple
way. MnBi₂Te₄ thin films can exhibit a quantum anomalous Hall effect [2] even in thinfilms that have no spin magnetism [3], and by virtue of their strong spin-orbit coupling
open up many new opportunities for electrical control of magnetic configurations.
Among these I will focus mainly on the possibility of establishing electrical reservoirs
for magnons.
[1] C. Lei, S. Chen, and A. H. MacDonald, PNAS 117, 27224-27230 (2020)[2] C. Lei et al., Phys. Rev. Mater. 5, 064201 (2021)[3] C. Lei, and A. H. MacDonald, Phys. Rev. Mater. 5, L051201 (2021)

SESSION 1 | 11:40-12:30

Quasi particles and coherence in nanosystems
Eiji Saitoh
The University of Tokyo, Japan

Various excitations in solids are described in terms of quasi particles such as electrons,
phonons, and magnons; based on the concept of quasi-particles, atomistic andmechanical understandings of material properties have been constructed. On theother hand, electron and nuclear spins give birth to pseudo-conservation of angularmomentum, which has brought about various spintronics functions. The rediscoveryof spin currents carried by quasi particles has made it possible to directly observe theangular momentum transport in solids, and various material functions driven by spincurrent have been found. By using spin current, the interference between the quasi
particles can also be realized in a controllable way, and recently it has become possible
to extract microscopic information of solids from the interference. In this talk, we will
give an overview of spintronics physics from the perspective of quasiparticles andtheir interference.
[1] E. Saitoh, M. Ueda, and H. Miyajima, Appl. Phys. Lett. 88, 182509 (2006)[2] K. Uchida et al., Nature 455, 778-781 (2008)[3] Y. Kajiwara et al., Nature 464, 262-266 (2010)[4] R. Takahashi et al., Nature Physics 12, 52-56 (2016)[5] Y. Shiomi et al., Nature Physics 15, 22–26 (2019)

Day 2SESSION 3

08:00-08:50

Tuesday, October 26, 2021

Chair: Masao Ogata (U. Tokyo, Japan)

Kitaev interactions in Co based quantum
magnets
N. Peter Armitage (Johns Hopkins U., USA)

08:50-09:40

Low-power, long-range spin transfer infrustrated magnets and other correlated systems
James G. Analytis (UC Berkeley, USA)

09:40-10:30

Chirality and quantum information
Dmitri Kharzeev (Stony Brook U., USA)

10:30-11:15

Panel Discussion

SESSION 3 | 08:00-08:50

Day 2
TuesdayOct 26, 2021

Kitaev interactions in Co based
quantum magnets
N. Peter Armitage
Johns Hopkins University, USA

Kitaev quantum spin liquids (QSLs) are exotic states of matter that are predicted tohost Majorana fermions and gauge flux excitations. However, so far all known Kitaev
QSL candidates are known to have appreciable non-Kitaev interactions that pushes
these systems far from the QSL regime. Co-based magnets have been proposed to beperhaps a more ideal platform for realizing Kitaev QSLs. In this talk I will show evidence
for a Kitaev interactions in both the quasi-one-dimensional ferromagnet CoNb₂O₆ aswell as the hexagonal magnet BaCo₂(AsO₄)₂. CoNb₂O₆ was believed to be the bestmaterial realization of a 1D Ising chain, showing evidence for a 1+1 D quantum criticalpoint and Kramers-Wannier duality. We have recently shown that that CoNb₂O₆ is welldescribed a model with bond-dependent interactions that we call the ‘twisted Kitaev
chain’, as these interactions are similar to those of the honeycomb Kitaev spin liquid.
The ferromagnetic ground state of CoNb₂O₆ arises from the compromise between two
axes. Owing to this frustration, even at zero, field domain walls have quantum motion,
which is described by the celebrated Su–Schriefer–Heeger model of polyacetylene andshows rich behaviour as a function of field.

Most recently, we have shown that thehoneycomb cobalt-based Kitaev QSL candidate, BaCo₂(AsO₄)₂, has dominant Kitaev
interactions. Due to only small non-Kitaev terms a magnetic continuum consistent
with Majorana fermions and the existence of a Kitaev QSL can be induced by a small
out-of-plane-magnetic field. Our results BaCo₂(AsO₄)₂ as a far more ideal version of
Kitaev QSL compared with other candidates.

If time allows, I will also discuss ourefforts to not just measure these materials spectroscopically, but also control themwith ultrafast THz pulses, which opens up a number of possibilities for quantum
information processing and control.

[1] J. Steinberg et al., Phys. Rev. B 99, 035156 (2019)[2] C.M. Morris et al., Nature Physics 17, 832–836 (2021)[3] X. Zhang, et al., https://arxiv.org/abs/2106.13418

SESSION 3 | 08:50-09:40

Day 2
TuesdayOct 26, 2021

Low-power, long-range spin transfer
in frustrated magnets and othercorrelated systems
James G. Analytis
University of California, Berkeley, USA

Research into new methods to control magnetic spin textures has been largely
focused on technological applications. However, complex magnets, particularly
those characterized by magnetic frustration, offer opportunities for ultra-low power
applications. This is due to two main characteristics of such systems: 1) the nearly
degenerate phase space of magnetic states available to such systems, and 2) novel
magneto-electric coupling available to these materials. In this work, we illustrateunusual mechanisms for spin transfer are available to such strongly correlated
systems, revealing potential opportunities for applications of quantum materials.

SESSION 3 | 09:40-10:30

Day 2
TuesdayOct 26, 2021

Chirality and quantum information

Dmitri Kharzeev
Stony Brook University and BNL, USA

Chirality is a common theme in many branches of modern science, from particle
physics to cosmology. In quantum physics, chirality plays an especially important role
due to the chiral structure of the Standard Model that is responsible for parity violation
in weak interactions. The chiral anomaly describes the transfer of chirality between
chiral fermions and gauge fields, and enables a new type of dissipation-free quantum
transport that has been observed in condensed matter systems and is currently understudy in the quark-gluon plasma. These phenomena may allow a new generation ofquantum devices. Also, the absence of dissipation in the anomalous transport has asimple interpretation in the language of quantum information.

Day 3SESSION 4

15:00-15:50

Wednesday, October 27, 2021

Chair: Kensuke Kobayashi (U. Tokyo, Japan)

Probing quantum matter in- and out-of
equilibrium on a large-scale atomic quantum
simulator
Immanuel Bloch (LMU Munich, Germany)

15:50-16:40

Beyond-Hermitian quantum physics
Masahito Ueda (U. Tokyo, Japan)

16:40-17:10

SESSION 5

17:20-18:10

Panel Discussion

Chair: Ryusuke Matsunaga (U. Tokyo, Japan)

Driven quantum materials
Andrea Cavalleri (MPI Hamburg, Germany)

18:10-19:00

Quantum spin liquid with fractionalized
excitations- make it real!
Hidenori Takagi (MPI Stuttgart, Germany & U. Tokyo, Japan)

19:00-19:30

Panel Discussion

SESSION 4 | 15:00-15:50

Day 3
Wednesday
Oct 27, 2021

Probing quantum matter in- and outof equilibrium on a large-scale atomic
quantum simulator
Immanuel Bloch
Ludwig Maximilian University of Munich, Germany

More than 30 years ago, Richard Feynman outlined his vision of a quantum simulator
for carrying out complex calculations on physical problems. Today, his dream has
become a reality in laboratories around the world. Ultracold atoms trapped in opticallattices provide a particular intriguing setting for realising such quantum simulatorswith the possibility to control and detect the systems down to the level of single
atoms on single lattice sites. In my talk, I will discuss select applications for suchneutral atom quantum simulators to probe quantum phases of strongly interacting
electronic systems, including hidden magnetic order, topological phases as well as
non-equilibrium dynamics that provide new paradigms for statistical physics. I will
discuss the status of the field and give an outlook on future scalability of the systems.

SESSION 4 | 15:50-16:40

Day 3
Wednesday
Oct 27, 2021

Beyond-Hermitian quantum physics

Masahito Ueda
The University of Tokyo, Japan

Beyond-Hermitian quantum physics has attracted a great deal of attention in many
subfields of physics due to remarkable advances in experimental techniques andtheoretical methods in AMO, condensed matter and nonequilibrium statisticalphysics [1]. A full knowledge of types and occurrence times of quantum jumps allows
a complete description of quantum trajectories. A subclass thereof without quantum
jumps can be described by a non-Hermitian Hamiltonian. Here symmetries, topologicalproperties and many-body effects of Hermitian physics are fundamentally altered.
Transposition and complex conjugation, which are equivalent in Hermitian physics,
become inequivalent in the non-Hermitian framework, leading to nontrivial topologicalphases [2] through unification and ramification of topological phases [3] and resulting in
38 symmetry classes instead of 10 in the Altland-Zirnbauer classification [4]. In randommatrices, transposition symmetry leads to two new universality classes of levelspacing statistics other than the Ginibre ensemble [5]. In many-body physics, nonhermiticity leads to the dynamical sign reversal of magnetic correlations in dissipative
Hubbard models [6] and anomalous g-theorem-violating reversion of renormalizationgroup flows in the Kondo problem [7].
[1] Y. Ashida, et al., Adv. Phys. 69, 249 (2020).
[2] Z. Gong, et al., Phys. Rev. X 8, 031079 (2018).
[3] K. Kawabata, et al., Nat. Commun. 10, 297 (2019).
[4] K. Kawabata, et al., Phys. Rev. X 9, 041015 (2019).
[5] R. Hamazaki, et al., Phys. Rev. Research 3, 023286 (2020).
[6] M. Nakagawa, et al., Phys. Rev. Lett. 124, 147203 (2020).
[7] M. Nakagawa, et al., Phys. Rev. Lett. 121, 203001 (2018).

SESSION 5 | 17:20-18:10

Day 3
Wednesday
Oct 27, 2021

Driven quantum materials

Andrea Cavalleri
Max Planck Institute, Hamburg, Germany

In this paper I will discuss the use of far infrared radiation to drive collective modes ofsolids, and how this opens up many new opportunities to manipulate the functional
properties of quantum materials. I will discuss how such functional control can beachieved in superconductors, ferroelectrics, magnets and topological materials.

SESSION 5 | 18:10-19:00

Day 3
Wednesday
Oct 27, 2021

Quantum spin liquid withfractionalized excitations- make it
real!
Hidenori Takagi
Max Planck Institute, Stuttgart, Germany &The University of Tokyo, Japan

In conventional magnetic materials, interactions between the spins lead to a phasetransition from a high-temperature disordered state to a magnetically ordered stateas the temperature is lowered. The transition is typically accompanied by singularities
in the thermodynamic observables at the transition point, and spontaneous symmetry
breaking and a reduction of the spin entropy to zero as the system enters a uniqueground state. However, the spin entropy can also be released without any symmetry
breaking, down to zero temperature, by forming a collective quantum spin state withlong-range quantum entanglement. This exotic state of matter is called a quantum
spin liquid. A goal of condensed matter physics is to discover new quantum phases
formed by the ensemble of interacting spins and charges in solids. The QSL is perhaps
one of the most exotic quantum phases known so far partly because of the nontrivial
elementary excitations and has been attracting the attention of condensed matterscientists for several decades.
In 2006 a theoretical breakthrough in the field of QSLs was reported. Alexei Kitaev
proposed a simple new model that is exactly solvable and that gives a QSL groundstate, in which the spins fractionalize into emergent quasiparticles — Majorana
fermions [1]. Soon after, a spin-orbital Jeff = 1/2 Mott insulator was identified in acomplex 5d iridium oxide. This led to a theoretical proposal for the realization of theKitaev model using Jeff = 1/2 pseudo-spins in an iridate and initiated a search for the
QSL state and the hidden Majorana fermions in a family of iridium and ruthenium
compounds [2]. I am going to talk about the rapid progress in the materialization Kitaev
QSL as well as the hunting of Majorana fermions through the detection of chiral edge
state.
[1] A. Kitaev, Ann. Phys. 321, 2-111 (2006)[2] H.Takagi et al., Nat. Rev. Phys. 1, 264–280 (2019)

Day 4SESSION 6

08:00-08:50

Thursday, October 28, 2021

Chair: Mio Murao (U. Tokyo, Japan)

Quantum computing algorithms and software
Kohei Itoh (Keio U., Japan)

08:50-09:40

Quantum channel capacities
Debbie Leung (U. Waterloo, Canada)

09:40-10:10

SESSION 7

10:20-11:10

Panel Discussion

Chair: Mio Murao (U. Tokyo, Japan)

Quantum simulation by quantum annealing
Hidetoshi Nishimori (TIT, Japan)

11:10-12:00

Quantum computer designs from today’s NISQ
processors to tomorrow’s fault-tolerant quantum
computers
Kae Nemoto (NII, Japan)

12:00-12:30

Panel Discussion

SESSION 6 | 08:00-08:50

Day 4
ThursdayOct 28, 2021

Quantum computing algorithms andsoftwareKohei M. Itoh
Keio University, Japan

Rapid advancement of quantum computer hardware calls for development of
quantum computing algorithms and software that can contribute to the advancementof science, engineering, and industry. Intuitively, quantum computers should exhibit
significant advantage when simulating objects are governed by the law of quantum
mechanics rather than classical mechanics. Such examples include simulation of
atomic and molecular states, chemical reaction, etc. Other directions involve utilizationof the quantum parallelism leading to simultaneous calculations involving seemingly
infinite combinations. The present talk introduces recent advances in quantum
computing algorithms and software developed at Keio University Quantum Computing
Center.

SESSION 6 | 08:50-09:40

Day 4
ThursdayOct 28, 2021

Quantum channel capacities

Debbie Leung
University of Waterloo, Canada

A quantum channel transmits a quantum state from a sender to a receiver, and canbe used to communicate various types of data (quantum, private, or classical) fromthe sender to the receiver, or to share entanglement between them. Noisy quantum
channels model the most general lossy quantum dynamics. When a noisy quantum
channel is used repeatedly in a memoryless manner, a quantum error correcting code
can be used to perform one of these tasks with less error but at a reduced rate; theultimate rate is called the capacity of the channel for the task.
In this talk, we will summarize major results in quantum channel capacities. Then, we
focus on various surprising quantum phenomena caused by entanglement between
different channel uses, resulting in high communication rates deemed implausible
under reasonable assumptions (for example, superadditivity, superactivation, andprivacy without coherence). The talk will be based on pedagogical results in thesubject, joint work with Felix Leditzky, Ke Li, Vikesh Siddhu, Graeme Smith, and John
Smolin, and some open problems.

SESSION 7 | 10:20-11:10

Day 4
ThursdayOct 28, 2021

Quantum simulation by quantum
annealing
Hidetoshi Nishimori
Tokyo Institute of Technology, Japan

Quantum annealing was designed to solve combinatorial optimization problems.
Recent years have seen its further developments in quantum simulation, i.e., tosimulate the properties of materials under strong quantum effects. I first review a few
important contributions in this rapidly-developing field and then explain our resultson the non-equilibrium quantum dynamics in the one-dimensional transverse-field
Ising model in the context of the Kibble-Zurek mechanism [1].

Also discussed is thelimit of simulability of quantum dynamics by simulated quantum annealing, a classicalstochastic algorithm, which is often used as an alternative tool of quantum annealing [2].
[1] Y. Bando et al., Phys. Rev. Res. 2, 033369 (2020)[2] Y. Bando, and H. Nishimori, Phys. Rev. A 104, 022607 (2021)

SESSION 7 | 11:10-12:00

Day 4
ThursdayOct 28, 2021

Quantum computer designs fromtoday’s NISQ processors to tomorrow’s
fault-tolerant quantum computers
Kae Nemoto
National Institute of Informatics, Japan

In the last decade, we have seen the emergence of small-scale quantum computerscommonly referred as NISQ processors. These quantum computational hardware
developments have stimulated research into software technologies. This has given us
the opportunity now to consider software layers for quantum computer technologies,
however the validity and scalability of these technologies are still in question. In thistalk, we explore the pros and cons of these NISQ processors. We will further discusspossibilities for small-scale quantum computers outside of the realm of today’s NISQ
processors. The technologies developed for NISQ processors brought the coherent
controllability of various quantum systems, which will open new opportunities in bothquantum physics and quantum computation. Finally, we will discuss the scalability ofthese quantum systems and identify the key challenges we face as we move forward
towards fault-tolerant quantum computers.
[1] M. P. Estarellas et al., Sci. Adv. 6, eaay8892 (2020)[2] M. Gong, et al., Science 372 (6545), 948-952 (2021)[3] K. Nemoto et al., Phys. Rev. X 4, 031022 (2014)

Day 5SESSION 8

08:00-08:50

Friday, October 29, 2021

Chair: Satoru Nakatsuji (U. Tokyo, Japan)

Emergent electromagnetic responses fromtopological magnets
Yoshinori Tokura (RIKEN & U. Tokyo, Japan)

08:50-09:40

Emergent quasi-particles in frustrated magnets
Collin Broholm (Johns Hopkins U., USA)

09:40-10:10

SESSION 9

10:20-11:10

Panel Discussion

Chair: Kenji Fukushima (U. Tokyo, Japan)

A simple model of many-particle entanglement:
how it describes black holes andsuperconductors
Subir Sachdev (Harvard U., USA)

11:10-12:00

Quantum aspects of inflationary cosmology
Jun'ichi Yokoyama (U. Tokyo, Japan)

12:00-12:50

Correlations and topology in twisted structures
Ashvin Vishwanath (Harvard U., USA)12:50-13:35

Panel Discussion

13:35-13:40

Closing Remarks
Masahito Ueda (U. Tokyo, Japan)

SESSION 8 | 08:00-08:50

Day 5
FridayOct 29, 2021

Emergent electromagnetic responses
from topological magnets
Yoshinori Tokura
RIKEN & The University of Tokyo, JapanThe topology of spin texture either in momentum space and real space can generate
emergent electromagnetic fields acting on the conduction and valence electrons
in solid, produce intriguing properties and responses. One archetypical example ismagnetic topological insulators, in which the spin-momentum locking as well as themagnetization-induced mass-gap shows up to form the ideal Weyl (spin-momentum
locked) fermion system at surface. With control of the magnetizations on the top
and bottom surfaces, quantum anomalous Hall state and quantum magnetoelectric(axion insulator) state can be realized. One other important example of topologicalmagnets is a magnetic skyrmion, which forms real-space spin-swirling texture withinteger winding number. Its real-space topology protects the skyrmion from external
perturbations, realizing a robust metastable state. Novel electromagnetic phenomena
arise from the topological spin textures, such as huge topological Hall effect (via Berrycurvature) and emergent electromagnetic induction (via temporal Berry connection).
These momentum-space or real-space topological spin textures are overviewed withperspectives of exploration for new quantum materials and functions.

SESSION 8 | 08:50-09:40

Day 5
FridayOct 29, 2021

Emergent quasi-particles in frustrated
magnets*
Collin Broholm
Johns Hopkins University, USA

Crystalline solids with Interacting local moments that do not fully order at low
temperatures can support a variety of strongly correlated electronic phenomena. Withno static magnetism or symmetry breaking, the quantum spin liquid (QSL) represents
an important albeit rare limit. A much larger variety of materials has been found tohave spin liquid like properties in restricted temperature and frequency regimes. I
shall describe experiments that explore such materials by scattering neutrons fromtheir emergent magnetic quasi-particles. The materials range from insulating rareearth oxides through transition metal oxides near the metal insulator transition to
Kondo semi-metals and heavy fermions systems. Conducted using the latest neutron
scattering instrumentation, the experiments offer detailed atomic scale insights
into strongly correlated phenomena that challenge conventional understanding ofmagnetism in solids.
*This work was supported as part of the Institute for Quantum Matter, an Energy Frontier ResearchCenter funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences underAward No. DE-SC0019331 and by the Gordon and Betty Moore foundation through the EPIQS
program GBMF9456.

SESSION 9 | 10:20-11:10

Day 5
FridayOct 29, 2021

A simple model of many-particle
entanglement: how it describes black
holes and superconductors
Subir Sachdev
Harvard University &Institute for Advanced Studies, Princeton, USA

Entanglement is the strangest feature of quantum theory, often dubbed ''spooky
action at a distance’’. Quantum entanglement can occur on a macroscopic scalewith trillions of electrons, leading to new forms of matter with properties oftechnological importance. Related entanglement structures arise across black holehorizons, giving rise to Hawking’s information puzzle. I will describe the SachdevYe-Kitaev model of many-particle entanglement which has shed light on these
distinct fields of physics [1,2,3].
[1] S. Sachdev and J. Ye, Physical Review Letters 70, 3339 (1993)[2] S. Sachdev, Physical Review Letters 105, 151602 (2010)[3] A. Kitaev, Talks at KITP Santa Barbara (2015)

SESSION 9 | 11:10-12:00

Day 5
FridayOct 29, 2021

Quantum aspects of inflationary
cosmology
Jun’ichi Yokoyama
The University of Tokyo, Japan

Four decades after its original proposal, inflationary expansion in the early Universe
is now regarded as an indispensable ingredient of modern standard cosmology which
not only explains fundamental properties of the global spacetime of our universe,
namely, why our universe is so large, so homogeneous, and so old with full of matters,
but also account for the origin of tiny density and curvature perturbations thateventually grow to all the cosmic structures we observe today [1]. The latter owes toquantum physics in the early universe; microphysical quantum fluctuations or zeropoint oscillation of the scalar field responsible for inflation is stretched to cosmologicalscales by virtue of exponential expansion of the background space. Observations of
the cosmic microwave background radiation, which is a fossil of the Universe at thetime of photon-baryon decoupling, 380 thousand years after the Big Bang, reveal good
agreement with the prediction of standard inflationary cosmology. To single out theright theory in high energy physics responsible for inflation from these observations is
one of the ultimate goals of the studies on inflationary cosmology. Recently we havecalculated one-loop correction to the power spectrum of curvature perturbations
generated during inflation and found a nontrivial constraint on the propagation speedof these fluctuations [2], which may be helpful to further constrain model building.
[1] K. Sato, and J. Yokoyama, Int. J. Mod. Phys. D24, 1530025 (2015)[2] J. Kristiano, and J. Yokoyama, https://arXiv.org/abs/2104.01953

SESSION 9 | 12:00-12:50

Day 5
FridayOct 29, 2021

Correlations and topology in twisted
structures
Ashvin Vishwanath
Harvard University, USAI will discuss recent progress in understanding correlated phases, including
superconductivity, in magic angle graphene, from a topological and quantum
geometric viewpoint [1]. A spectacular application of these concepts predicts a
fractional Chern insulator in graphene at certain fillings, which is borne out by
recent experiments [2]. Finally, I will discuss twisted structures built out of correlatedmaterials. In particular, I will review our recent results on a t-J model approach totwisted bilayer cuprates, and prospects for acquiring new insights into the old problemof doped Mott insulators using twisted structures [3].
[1] P. J. Ledwith, E. Khalaf, and A. Vishwanath, https://arXiv.org/abs/2105.08858[2] Y. Xie et al., https://arXiv.org/abs/2107.10854[3] X.-Y. Song, Y.-H. Zhang, and A. Vishwanath, https://arXiv.org/abs/2109.08142

ABOUT THE TRANS-SCALEQUANTUM SCIENCE INSTITUTE

The Trans-Scale Quantum Science Institute was established on February 1st, 2020
with the objective of forming a research platform encompassing all scales of quantum
science, including cosmology, particle physics, condensed matter physics, quantum
information and mathematics. The creation of the Institute was based on the observationthat recent discoveries have come about by introducing ideas from branches of physics
that are unrelated at first glance. For instance, topological gauge-field theories proposedin high energy physics are now recognized as models for topological phases in mattersuch as quantum Hall systems, and are drawing attention as a promising platform
for fault tolerant quantum computation and quantum memory. Another example isthat of Weyl fermions, which had been introduced as a model of neutrinos and werediscovered in solid-state materials recently, leading to the development of novel highspeed memory.

With this in mind, we aim to drive innovation by fostering interdisciplinary researchand leveraging the active interplay between multiple areas to make experimental
discoveries, formulate novel theories and create concepts and fields that encompass
physics of various scales. Moreover, we aim to make an impact on society by pushing
forward the development of future technologies, and by training young talent to master
quantum science at various levels and equip them with the necessary skills to continue
the long-term development of these technologies.

Presently, the Institute is formed by over 30 leading researchers from the School of
Science, the Institute for Solid State Physics, the Cryogenic Research Center and the
Kavli Institute of Mathematics and Physics of the Universe, all part of the University ofTokyo. The Institute also maintains a close relationship with researchers from institutions
from around the world, such as Princeton University, Johns Hopkins University, the Max
Planck Institutes, The University of British Columbia, and the École Normale Supérieureamong several others, with the objective of forming an international research platform
and facilitating the mobilization of human resources, from faculty members to young
researchers, and accelerate scientific discovery.

ABOUT JSR CORPORATIONJSR Corporation is a research-oriented, multinational company focused on the digital solutions,
including semiconductor, and life sciences markets. Headquartered in Tokyo, Japan, JSR has
facilities and offices throughout Asia, Europe and the US. JSR’s customer-centric approachpursues sustainability and resilience through close collaborations, all with a focus on driving
innovation to provide value to the world’s leading-edge industries. For more information about
JSR Corporation, please go to www.jsr.co.jp.

CREATING MATERIALS FOR THE FUTURE THROUGH
MATERIALS INNOVATIONWith deep expertise in its core polymer and precision manufacturing technologies, the JSR Grouphas widened the scope of its technological domains by integrating technologies from disparate
fields such as photochemistry, inorganic chemistry, precision processing and biotechnologies.
Also, it is important for us to understand and pursue fundamental principles, including in-depth
research into analysis and evaluation technologies. On this basis, the Group has advanced R&D
activities, and the accumulated efforts have enabled it to develop unique strengths relative
to chemical companies worldwide, which is our driving force to expand our materials andtechnologies globally.

R&D Policy and
Structure

OCTOBER 25-29, 2021, JST ONLINE CONFERENCE

ORGANIZING COMMITTEE(TRANS-SCALE QUANTUM SCIENCE INSTITUTE, THE UNIVERSITY OF TOKYO):

Kenji Fukushima
Masamitsu Hayashi
Kensuke Kobayashi
Ryusuke Matsunaga
Satoshi Miyashita
Mio Murao
Satoru Nakatsuji
Masao Ogata
Masaki Oshikawa

SECRETARIAT
Sergio Andraus
Yasuyo Eguchi
Yusuke Horinouchi
Hiroko Seike
Sachiko Shimizu
Mai Yamashita

www.tsqs2021.org