Abstract: Research of cavity quantum electrodynamics (CQED) has enabled new capabilities in light-matter interactions, quantum optics, and various quantum technologies. So far, all the work in this field has included light interacting with bound-electron systems such as atoms, quantum dots, and quantum circuits. In contrast, free-electron systems enable fundamentally different physical phenomena, as their energy distribution is continuous and not discrete, allowing for tunable transitions and selection rules.
We have developed a platform for studying free-electron CQED at the nanoscale. We demonstrated it by observing the first coherent interaction of a free electron with a photonic cavity and first interaction with the quantum statistics of photons. Our platform is based on a laser-driven transmission electron microscope, which created what is, in many respects, the most powerful nearfield optical microscope in the world today. We use it to resolve photonic bandstructures as a function of energy, momentum, and polarization, simultaneously with capturing the spatial distribution of the photonic modes at deep-subwavelength resolution. This way, our microscope enables recording the spatiotemporal dynamics of light in nanophotonic structures and of phonon polaritons in 2D materials.
These capabilities open new paths toward using free electrons as carriers of quantum information. Looking forward, we propose to create free-electron qubits and implement quantum gates with femtosecond lasers. We show how such free-electron probes can measure quantum coherence and decoherence rates of individual quantum systems on the nanoscale.
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· R. Ruimy†, A. Gorlach†, C. Mechel, N. Rivera, and I. Kaminer, Towards atomic-resolution quantum measurements with coherently-shaped free electrons, Phys. Rev. Lett. 126, 233403 (2021)
· O. Reinhardt†, C. Mechel†, M. H. Lynch, and I. Kaminer, Free-Electron Qubits, Annalen der Physik 533, 2000254 (2021)
· Y. Kurman†, R. Dahan†, H. Herzig Shenfux, K. Wang, M. Yannai, Y. Adiv, O. Reinhardt, L. H. G. Tizei, S. Y. Woo, J. Li, J. H. Edgar, M. Kociak, F. H. L. Koppens, and I. Kaminer, Spatiotemporal imaging of 2D polariton wavepacket dynamics using free electrons, Science 372, 1181 (2021)
· R. Dahan†, A. Gorlach†, U. Haeusler†, A. Karnieli†, O. Eyal, P. Yousefi, M. Segev, A. Arie, G. Eisenstein, P. Hommelhoff, and I. Kaminer, Imprinting the quantum statistics of photons on free electrons, Science 373, 6561 (2021)