Dr. Igor Khanonkin Quantum Light in van der Waals Heterostructures: From Ultrastrong Coupling in the Terahertz Regime to Quantum Sensing with Atomic Resolution

Quantum Light in van der Waals Heterostructures: From Ultrastrong Coupling in the Terahertz Regime to Quantum Sensing with Atomic Resolution Dr. Igor Khanonkin Abstract Two-dimensional (2D) materials provide a versatile platform for engineering light–matter interactions across vastly different regimes, paving the way toward quantum systems with tailored properties. In this talk, I will present results that outline a unified framework in which 2D materials bridge condensed matter physics and quantum optics, opening new directions for cavity-controlled electronic phases, collective emission, and quantum sensing at the atomic scale. I will begin by describing the development of a sub-diffraction terahertz (THz) spectroscopy technique [1], which enabled the first demonstration of ultrastrong coupling between THz cavity modes and a tunable interband transition in bilayer graphene device. The observed cavity-induced resonance emerges from the interband continuum and mimics a Coulomb-bound exciton. These experiments reveal a coupling strength exceeding 40% of the mode frequency, marking the onset of a non-perturbative regime of hybrid exciton–photon states in quantum materials. Next, I will discuss how optically active defects in hexagonal boron nitride (hBN) provide a promising platform for quantum sensing with atomic-scale resolution [2]. Unlike NV centers in diamond, which lie about 10 nm below the surface and thus limit spatial resolution, B-centers in hBN can reside within only a few atomic layers of the target material. This enables their integration into van der Waals heterostructures and AFM-like tips to directly visualize Moiré patterns and strongly correlated electronic states with nanometer precision. Finally, I will present our observation of superradiance in ensembles of quantum emitters in hBN, where emitters separated by sub-wavelength distances collectively emit photons in short, intense bursts—exhibiting the hallmark signatures of cooperative spontaneous emission. [1] F. Helmrich, H.S. Adlong, I. Khanonkin, M. Kroner, G. Scalari, J. Faist, A. Imamoglu, T.F. Nova. “Cavity-Driven Attractive Interactions in Quantum Materials”. Preprint arXiv:2408.00189v3 (2024). [2] L. Liu*, I. Khanonkin*, J. Eberle*, B. Rizek, S. Falt, K. Watanabe, T. Taniguchi, A. Imamoglu and M. Kroner. “Quantum Emitters in Ultra-Thin Hexagonal Boron Nitride Layers”, Preprint arXiv:2507.02633v1 (2025). Short Bio Dr. Igor Khanonkin is a Rothschild Postdoctoral Fellow at ETH Zurich’s Institute of Quantum Electronics, where he drives two pioneering research directions in Prof. Atac Imamoglu’s group: THz cavity quantum electrodynamics and super-resolution quantum sensing using optical active defects in 2D materials. He completed his PhD at the Technion, Faculty of Electrical and Computer Engineering, under the supervision of Prof. Gadi Eisenstein, focusing on nonlinear and quantum photonics. Dr. Khanonkin also established Israel’s participation in the International Physicists’ Tournament (IPT).