Oral Session C3 (Thursday, February 15)
Chair: Naoki Yamamoto, Keio University

Special Session Talk
13: 30 - 14 : 10

Gordon Baym
The University of Illinois at Urbana-Champaign (UIUC)

Matter under extreme conditions in neutronstars
Neutron stars -- of masses up to a little more than twice that of the sun, and yet compressed bygravity down to tens of kilometers -- are the densest objects in the universe [1]. As such they arenatural laboratories for studying the properties of matter under extreme conditions of density andpressure not readily achievable on Earth. Indeed, very shortly after the discovery of the BCS
theory of superconductivity, familiar ideas of condensed matter physics began to play an importantrole in unraveling the physics of neutron stars -- from the existence of a solid crust to superfluid
states of the nucleons, neutrons and protons, in the interior. In this talk I will give a general
overview of the condensed matter physics in neutron stars interiors, including cutting edge
questions of the role of quarks (the internal constituents of neutrons and protons) in the deep
interior. For example, how does a superfluid of neutrons and protons transition to superfluid
quark matter in the deep interior, and how can such superfluid quark matter carry angularmomentum [2].
References[1] Reviewed in G. Baym, T. Hatsuda, T. Kojo, P. D. Powell, Y. Song, and T. Takatsuka, Rpts. on Prog. inPhysics 81 (2018) 056902.
[2] M. G. Alford, G. Baym, K. Fukushima, T. Hatsuda, and M. Tachibana, Phys. Rev. D 99, 036004 (2019).

Oral Session C3 (Thursday, February 15)
Chair: Naoki Yamamoto, Keio University

Contributed Oral
14: 10 - 14 : 30Nonrelativistic trace anomaly and its impact on equationof state in dense fermionic matter: Toward understanding
hadron-quark crossover via analogue quantum simulation
H. Tajima1, K. Iida2, and H. Liang1, 3
1. Department of Physics, Graduate School of Science, The University of Tokyo, Japan
2. Department of Mathematics and Physics, Kochi University, Japan
3. Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS), RIKEN, Japan
Recent observations of neutron stars suggest that nuclear matter gradually changes into dense quark matter withincreasing density [1]. A remarkable feature of this structural change lies in the presence of a sound velocity peak in
the hadron-quark crossover regime [2]. However, the microscopic mechanism of the hadron-quark crossover iselusive because it is observationally diﬃcult to obtain detailed information on the properties of matter in the star.
Recent lattice two-color quantum chromodynamics simulation [3] shows the existence of such a peak and implies
similarities with the Bose-Einstein-condensation (BEC) to Bardeen-Cooper-Schrieﬀer (BCS) crossover realized inultracold atoms. In this regard, analogue quantum simulation could be a promising route to elucidate the crossovermechanism. According to the quantum Monte Carlo simulation of one-dimensional three-component
nonrelativistic Fermi gases [4], this system simultaneously exhibits a sound velocity peak and a crossover fromdeeply to loosely bound trimers, which has been discussed in connection with the three-body counterpart of
Cooper pairs, namely, Cooper triples [5]. In this contribution, we discuss eﬀects of trace anomaly involving
three-body correlations on the equation of state in this system by using the Brueckner G-matrix approach known
to successfully describe the equation of state in the BCS-BEC crossover [6].
References[1] T. Kojo, G. Baym, and T. Hatsuda, ApJ 934 46 (2022).
[2] T. Kojo, AAPPS Bull. 31, 11 (2021).
[3] K. Iida, and E. Itou, Prog. Theor. Exp. Phys. 2022, 111B01 (2022).
[4] J. R. McKenney, A. Jose, and J. E. Drut, Phys. Rev. A 102, 023313 (2020).
[5] H. Tajima, S. Tsutsui, T. M. Doi, and K. Iida, Phys. Rev. Research 4, L012021 (2022).
[6] H. Sakakibara, H. Tajima, and H. Liang, Phys. Rev. A 107, 053313 (2023).

Oral Session C3 (Thursday, February 15)
Chair: Naoki Yamamoto, Keio University

Special Session Talk
14: 30 - 15 : 10

Surjeet RajendranDepartment of Physics and Astronomy, Johns Hopkins University

Fundamental physics with quantum sensors
The search for new physical laws and particles has largely been driven by the expectation that thenew physics lies at high energies with reasonably strong interactions with the standard model.
However, the existence of dark matter and dark energy, as well as the potential new physics that
could be discovered using gravitational waves, suggests that there is a strong case to search forphenomena that do not interact much with the standard model. The discovery of suchphenomena requires precision sensing. The remarkable advances that have occurred in the field of
quantum metrology in the past three decades have made it possible to deploy a wide variety ofquantum sensors to detect such ultra-weakly coupled physics. In this talk, I will discuss a variety of
new experimental methods that can be used to detect gravitational waves in the 1 Hz frequency
band between LIGO and LISA and probe a wide variety of dark matter candidates in thelaboratory.

Oral Session C3 (Thursday, February 15)
Chair: Naoki Yamamoto, Keio University

Contributed Oral
15: 10 - 15 : 30

Braiding and fusion of Majorana fermions in minimal
Kitaev spin liquid on a single hexagon with 5 qubits
Motohiko Ezawa
1. Department of Applied Physics, University of Tokyo, Japan
We propose the minimal Kitaev spin liquid on a single hexagon with three Ising-type exchange interactions
proportional to Kx, Ky and Kz. In the limit Kz=0, we find 32-fold zero-energy states, leading to 10 free Majorana
fermions, and hence, 5 qubits are constructed. These qubits are protected by particle-hole symmetry even for Kz≠0.
Braiding of these Majorana fermions is possible by temporally controlling a spin-correlation Hamiltonian. Inaddition, the fusion is possible by measuring spin correlations. By switching on the Heisenberg interaction together
with magnetic field, only one zero-energy state persists, which can be used as an initialization of qubits.
Furthermore, it is shown that 3L+2 qubits are constructed on the Kitaev spin liquid model on connected Lhexagons. All the processes of initialization, operation and readout of qubits are executable in terms of spin operators.

References[1] Motohiko Ezawa, Braiding and fusion of Majorana fermions in minimal Kitaev spin liquid on a single hexagon with 5 qubits,
arXiv:2401.01051

Oral Session C3 (Thursday, February 15)
Chair: Naoki Yamamoto, Keio University

Contributed Oral
15: 30 - 15 : 50

Integrating ultrafast switches into a single molecule
Hirofumi Yanagisawa
Shizuoka University, Japan
Irradiating a sharp metallic needle with femtosecond light pulses generates electron emissions from the apex[1], as
depicted in Figure 1(a). These emissions serve as ultrafast switches, significantly surpassing the speed of current
computer switching devices by three to six orders of magnitude. Concurrent plasmonic eﬀects enable precise spatial
control of electron emission on a 10-nm scale[2]. Leveraging this phenomenon allows the selection of emission sites
A or B in Figure 1(b), resembling two integrated transistor switches independently controlled by light in theaccompanying diagram. Consequently, this site selectivity aids switch integration. However, further miniaturizationof such an electron source through plasmonics poses challenges. Here, we propose a new approach utilizing thequantum nature of a single-molecule. In this setup, fullerene molecules are positioned on a metallic substrate[3], as
illustrated in Figure 1(c). Electrons, supplied from the substrate, are emitted from the single molecules after traversing
specific molecular orbitals (MOs). Depending on the involved MOs, the emission sites vary. Our researchdemonstrates the potential to optically manipulate the MOs that electrons pass through, thus enabling the creationof an electron source with subnanometric emission site-selectivity[4]. This technique facilitates the integration ofswitches into a single molecule.
References[1] P. Hommelhoﬀ, et al., Phys. Rev. Lett. 96, 077401 (2006).
[2] H. Yanagisawa, et al., Phys. Rev. Lett. 103, 257603 (2009).
[3] H. Yanagisawa, et al., Sci. Rep. 12, 2174 (2022).
[4] H. Yanagisawa, et al., Phys. Rev. Lett. 130, 106204 (2023).