Interaction of Light and Matter Controlled at the Single Electron Level and Its Application to Quantum Information Processing Technologies
In recent years, there has been vigorous research and development focused on utilizing electrons or their spins confined in semiconductor quantum dots as quantum information carriers (qubits) for quantum information processing. Since it has been known that millions of qubits will be needed for practical quantum computing in the future, the extension and integration of qubits is considered one of the most pressing challenges for large-scale quantum computers. Currently, one of the most promising approaches is to exploit the light-matter interaction to facilitate qubit integration. Our research group conducts fundamental research on quantum transformations realized between electrons confined in quantum dots and electromagnetic waves confined in terahertz metamaterial optical resonators. We have successfully realized light-matter coupling states between a few electrons confined in quantum dots and a terahertz optical resonator. In the future, we intend to develop research on controlling the coupling state of a single electron and the resonator, and realize remote coupling of single electrons via terahertz electromagnetic waves.
References:
K. Kuroyama, J. Kwoen, Y. Arakawa, K. Hirakawa, “Coherent Interaction of a Few-Electron Quantum Dot with a Terahertz Optical Resonator” Phys. Rev. Lett. 132, 066901 (2024).
Exploring the Physics of Extremely strong Light-Matter Interaction
When light and matter are strongly coupled, they create new quantum hybrid states, which acquire both light and matter properties, called “polaritons”. In addition, when light or electromagnetic waves are strongly confined to a microscopic region and the electric field strength is significantly increased using metamaterial resonators, the coupling energy between light and matter can become comparable to the energy of single photons in an optical resonator. Such significantly strong light-matter coupling is called ultrastrong coupling, and they are expected to induce intriguing quantum phase transition phenomena in materials and enable novel control technologies of matter. Our research group has achieved ultrastrong coupling between electrons in semiconductor nanostructures and terahertz electromagnetic waves by growing high-quality semiconductor heterostructures and combining them with terahertz-band metamaterial optical resonators. We will continue to expand experimental research to explore novel quantum phase transition phenomena predicted for polaritons in the ultrastrong coupling regimes.
References:
J. Huang, J. Kwoen, Y. Arakawa, K. Hirakawa, K. Kuroyama, “Chiral terahertz photocurrent in quantum point contact–split ring resonator coupled systems in the quantum Hall regime” Phys. Rev. B 111, L121407 (2025).
K. Kuroyama, J. Kwoen, Y. Arakawa, K. Hirakawa, “Electrical Detection of Ultrastrong Coherent Interaction between Terahertz Fields and Electrons Using Quantum Point Contacts” Nano Lett. 2023, 23, 24, 11402–11408 (2023).