Cavity nano-optics with configurable interaction: room temperature strong coupling of single emitter

Quantum state control of two-level emitters is fundamental for many information processing, metrology, and sensing applications. However, quantum-coherent photonic control of solid-state emitters has traditionally been limited to cryogenic environments, which are not compatible with implementation in scalable, broadly distributed technologies. In contrast, plasmonic nano-cavities with deep sub-wavelength mode volumes have recently emerged as a path towards room temperature quantum state hybridization and control. Here we establish plasmonic tip-enhanced strong coupling (TESC) with a configurable nano-tip cavity to modulate and control the cavity-emitter interaction with sub-nanometer precision, quantify coupling strength exceeding ~160 meV, at mode volumes of < 10^-6 λ³, augmented by theoretical modeling. Based on this work, we provide a perspective for nano-cavity optics as a promising tool for room temperature control of quantum coherent interactions that could spark new innovations in fields from quantum information and quantum sensing to quantum chemistry and molecular opto-mechanics.