2008/03/19 by I. Schuster, Alexander Kubanek, A. Kubanek +9 · 3 citations
Computer Science · Engineering · Physics and Astronomy · #Atom (system on chip) #Atomic physics #Cavity quantum electrodynamics #Laser #Mechanical and Optical Resonators #Nonlinear optics #Nonlinear system #Open quantum system #Optical cavity #Optics #Photon #Photonic and Optical Devices #Physics #Quantum #Quantum Information and Cryptography #Quantum mechanics #Quantum optics #Resonance (particle physics) #Spectroscopy #cond-mat.other #quant-ph
paper · pdf · doi:10.1038/nphys940
published as Nature Physics 4, 382-385 (2008) · 7 figures, Nature Physics
arxiv created 2008/03/19 · openalex publication_date 2008/04/13 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Optical nonlinearities typically require macroscopic media, thereby making their implementation at the quantum level an outstanding challenge. Here we demonstrate a nonlinearity for one atom enclosed by two highly reflecting mirrors. We send laser light through the input mirror and record the light from the output mirror of the cavity. For weak laser intensity, we find the vacuum-Rabi resonances. But for higher intensities, we find an additional resonance. It originates from the fact that the cavity can accommodate only an integer number of photons and that this photon number determines the characteristic frequencies of the coupled atom-cavity system. We selectively excite such a frequency by depositing at once two photons into the system and find a transmission which increases with the laser intensity squared. The nonlinearity differs from classical saturation nonlinearities and is direct spectroscopic proof of the quantum nature of the atom-cavity system. It provides a photon-photon interaction by means of one atom, and constitutes a step towards a two-photon gateway or a single-photon transistor.