Session1 : Quantum Photonics

13:30 - 14:15  | 
  Lecture,  

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Manipulating light is critical for scaling quantum technologies. I will describe our efforts harnessing mature, wafer scale, wide-bandgap semiconductor photonics to create distributed entangled states [1]. In this material, we have demonstrated the world record longest electron [2] and nuclear spin [3] coherence times of embedded optically active defect qubits. I will then present our most recent results on the discovery of a different material with the largest electro-optic nonlinearity ever reported at cryogenic temperatures [4]. Finally, I'll overview the opportunities for this previously unexplored material for use in photonic quantum computing, microwave-to-optical transduction, and for scaling superconducting processors with light.

[1] C. P. Anderson and D. D. Awschalom. Physics Today 76 (8), 26–33 (2023)

[2] C. P. Anderson*, E. O. Glen*, C. Zeledon, A. Bourassa, Y. Jin, Y. Zhu, C. Vorwerk, A. L. Crook, H. Abe, J. Ul-Hassan, T. Ohshima, N. T. Son, G. Galli, and D. D. Awschalom. Science Advances 8, 5 (2022)

[3] C. Zeledon, B. Pingault, J. C. Marcks, M. Onizhuk, Y. Tsaturyan, Y. Wang, B. S. Soloway, H. Abe, M. Ghezellou, J. Ul-Hassan, T. Ohshima, N. T. Son, F. J. Heremans, G. Galli, C. P. Anderson, D. D. Awschalom. arXiv:2504.13164 (2025)

[4] C. P. Anderson, G. Scuri, A. Chan, S. Eun, C. Jilly, A. Safavi-Naeini, K. Van Gasse, L. Li, and J. Vučković. arXiv:2502.15164, Science (in press) (2025)

  Session2 : Quantum Materials

14:15 - 15:00  | 
  Lecture,  

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Many quantum materials, ranging from magnetic, superconducting to topological materials, are interesting due to their characteristic and unique spin degrees of freedom. In this lecture, we will discuss how various experimental techniques developed in spintronics and magnetics, can be applied to study such quantum materials. Examples include: spin-sensitive transport in topological insulators (with characteristic helical spin momentum locking that may have application to enable a spin injection and spin battery sources for electronic and even nuclear spintronics); magneto-optical-Kerr-effect (MOKE) and spin-sensitive transport measurements such as magnetic-tunneling-junctions and spin-hall-magnetoresistance measurements on 2D/van der waals (vdW) magnets --- ranging from twisted magnets (exhibiting noncollinear Moire magnetism, a magnetic analog of metamaterials with alternating ferro and antiferromagnetism) to “quantum” magnets (spin liquids). Time permits, additional examples such as spin-dependent STM (scanning tunneling microscopy) and quantum sensing using spin qubits (NV centers or other spin defect centers) are also discussed.

[1] J. Tian et al. Scientific Reports 5, 14293 (2015)

[2] J. Tian et al. Nature Communications 10, 1461 (2019)

[3] J. Tian et al. Science Advances 3, e1602531 (2017)

[4] H.Idzuchi et al. Applied Physics Letters 115, 232403 (2019)

[5] H. Idzuchi et al. Physical Review B 111,L020402 (2025)

[6] H. Idzuchi et al. arXiv:2204.03158

[7] G. Cheng et al. Nature Electronics, 6, 434 (2023)

[8] G. Cheng et al. Nature Communications 13, 7348 (2022)

[9] S.M.Hus et al. Physical Review Letters 119, 137202 (2017)

[10] A. Solanki et al. Physical Review Research 4, L012025 (2022)

[11] M.Sadi et al. Nano Letters 25, 12067 (2025)

15:00 - 15:25  | 
  Invited,  

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The construction of Landau-level-type flat bands is crucial for realizing topological phases and fractionalized phenomena in ultracold atomic systems. The Kapit-Mueller model, a special class of the Hofstadter model, realizes an exactly flat band with wavefunctions that are identical to the lowest Landau level states on a lattice. Its construction relies on the Poisson summation property of coherent states. In this work, we generalize this Poisson summation rule to higher Landau level states. Based on this generalization, we derive a family of Hofstadter-type models that support exact flat bands with wavefunctions corresponding to arbitrary high Landau level states.

15:25 - 15:45  
    ―  Coffee Break  ―

15:45 - 16:10  | 
  Invited,  

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The study of magnetic phenomena has remained a central theme in condensed matter physics, and in recent years, new types of magnetism have continued to be discovered, including orbital magnetism in stacked graphene systems and Altermagnetism. To advance the understanding of such novel systems and to explore new functionalities to go beyond the present electronics, it is essential to identify the corresponding order parameters and to elucidate their characteristic emergent phenomena.

From the viewpoint of symmetry, magnetic materials can be classified in terms of magnetic multipoles [1]. While the magnetic dipole class, to which conventional ferromagnets belong, and the magnetic quadrupole class, exemplified by multiferroic materials, have been extensively studied, the magnetic octupole class, including altermagnet, has recently begun to attract attention [2]. Such a classification provides a powerful framework to organize novel transport and optical phenomena, and at the same time, the multipoles themselves can serve as relevant order parameters for magnetic ordering.

In the theoretical evaluation of magnetic multipoles, quantum geometry naturally comes into play. Orbital magnetization, as well as higher-order multipoles, inherently involve orbital effects, and they are naturally characterized by quantum-geometric quantities such as the Berry curvature and the quantum metric [3].

In this presentation, we will discuss two topics on magnetic multipoles. One is the quantum-geometric quantification of magnetic octupole in crystals, illustrated with altermagnet as an example [4]. The other concerns orbital magnetization, with an emphasis on the geometric aspects, and we discuss an inequality induced by the geometric structure, keeping in mind similarity to the lowest Landau level in stacked graphene systems [5].

[1] N. A. Spaldin, et al., J. Phys. Condens. Matter 20, 434203 (2008)

[2] S. Bhowal and N. A. Spaldin, Phys. Rev. X 14, 011019 (2024)

[3] D. Xiao, et al., Phys. Rev. Lett. 97, 026603 (2006)

[4] J. Oike, R. Peters, and KS, arXiv:2504.21418

[5] KS and N. Nagaosa, arXiv:2507.12836

16:10 - 16:35  | 
  Invited,  

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The terahertz (THz) frequency (0.1–10 THz) lies in the electromagnetic spectrum between the microwave band and infrared band. It offers a powerful, low-energy probe for fundamental dynamics of charge, spin, and lattice vibrations in condensed matter. The development of efficient, broadband, and high-quality THz emitters remains a key challenge, often referred to as the "THz gap." Spintronic heterostructures have recently emerged as a revolutionary platform for generating gapless, ultra-broadband THz radiation. Moving beyond passive sources, achieving active, real-time control over the properties of this THz emission, particularly via an electric field, is the next crucial step for enabling advanced applications ranging from high-speed communications and signal processing to sophisticated spectroscopy.

One promising approach for controlling THz waves is by using piezoelectric strain. We demonstrated this by applying an external electric field to a piezoelectric substrate, which generated strain that was transferred to a thin magnetic film. This strain-mediated magnetic change allows us to actively tune the amplitude of the emitted THz pulses [1]. Further, we demonstrate giant, non-volatile electrical control of spintronic THz emission by engineering the quantum geometry of a topological Dirac semimetal, PtTe₂ [2]. By using a ferroelectric substrate to electrically tune the Fermi level across the Dirac point's concentrated Berry curvature, we achieve a robust 21% modulation of the spin-to-charge conversion. Our approach, corroborated by density functional theory, establishes quantum geometry engineering as a low-power, non-volatile, and powerful route for creating active THz spintronic components, opening new avenues for programmable spin-based logic and ultrafast electronics.

[1] A. Chaurasiya, Z. Li, R. Medwal, S. Gupta, J. R. Mohan, Y. Fukuma, H. Asada, E. E. M. Chia, and R. S. Rawat, Adv. Opt. Mater. 10, 2201929 (2022).

[2] Z. Li, D. Yang, F. Wang, Y. Yang, Y. Guo, D. Bao, T. Yin, C. S. Tang, T. Salim, L. Xi, C. Boothroyd, Y. M. Lam, B. Peng, M. Battiato, H. Yang, and E. E. M. Chia, Nano Lett. 25, 9006 (2025).

  Session3 : Correlations and Multipoles

16:35 - 17:00  | 
  Invited,  

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Recently, T. Ozaki has developed a new method to construct closest Wannier (CW) orbitals to a given set of localized guiding orbitals [1]. In the CW formalism, the disentanglement of bands is achieved with no iterative calculations, significantly reducing computational costs.

In this talk, we will present a generation scheme of the CW model that respects the symmetry of the system by introducing the post-processing symmetrization step based on the symmetry-adapted multipole basis (SAMB) [2]. Since the symmetry properties of the CW orbital and its guiding atomic orbital are equivalent, we can define SAMBs as the complete and orthonormal matrix basis set in the Hilbert space of the CW orbitals. Utilizing the completeness and orthonormality of SAMBs, the CW Hamiltonian can be expressed as a linear combination of SAMBs belonging to the identity irreducible representation, thereby fully restoring the symmetry of the system. Moreover, the linear coefficients of each SAMB (model parameters) related to crystalline electric fields, spinorbit coupling, and electron hoppings are determined through simple matrix projection without any iterative procedure. Thus, this method allows us to unveil mutual interplay among hidden electronic multipole degrees of freedom in the Hamiltonian and numerically evaluate them.

Using the symmetry-adapted CW model of chiral Te crystal, we discuss predominant order parameters for structural chirality and demonstrate that time-reversal-even axial quadrupole plays a key role in stabilizing a chiral structure [3]. We quantify the evolution of the spin-independent (spinless) and spin-dependent (spinful) electric toroidal (ET) (axial) multipole moments across the transition from an achiral to a chiral structure. Our results clearly identify that a spin-independent off-diagonal real hopping between p orbitals, which corresponds to the bond-cluster spinless ET quadrupole of (3z²-r²) type G_u, is the predominant order parameter in stabilizing helical structures.

[1] T. Ozaki, Phys. Rev. B 110, 125115, (2024).

[2] RO, A. Inda, S. Hayami, T. Nomoto, R. Arita, and H. Kusunose, Phys. Rev. B 112, 035116 (2025).

[3] RO, H. Kusunose, Phys. Rev. Research 7, 033250 (2025).

17:00 - 17:25  | 
  Invited,  

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Theoretical and computational tools for quantitatively simulating solids and molecules are deeply integrated across a range of scientific disciplines, from condensed matter physics and materials science to chemistry and biochemistry. By connecting emergent behaviors to microscopic origins, these tools enable interdisciplinary research and new material development.

Currently, most simulations of quantum matter use tools based on Density Functional Theory (DFT), but these approaches are not always reliable for materials containing transition metals, lanthanides, or actinides, where strong electron correlations often dominate the electronic structure. These strong correlations, related to the “multiconfigurational problem” in chemistry, underlie phenomena like magnetism and hightemperature superconductivity. The need to explain the unique emergent behavior of strongly correlated systems and accurately predict their structural and chemical properties has led to the development of accurate many-body techniques. However, computational cost currently prevents their widespread use for materials discovery, particularly for demanding tasks like structural relaxations or the exploration of complex reaction pathways essential for materials design.

We will introduce the Ghost Gutzwiller Approximation (gGA), a quantum embedding framework with accuracy comparable to Dynamical Mean-Field Theory (DMFT) in simulating the quantum-mechanical properties of strongly correlated materials, while significantly reducing computational demands. We will present recent technical advancements and real-material benchmark calculations, emphasizing the integration of machine-learning techniques to extend the “materials-by-design” paradigm to strongly correlated matter, moving beyond traditional DFT approximations while maintaining computational feasibility.