# Tip-enhanced strong coupling spectroscopy, imaging, and control of a single quantum emitter

## TL;DR

This paper introduces tip-enhanced strong coupling (TESC) spectroscopy that dynamically controls and probes single quantum emitters with nanoscale precision, enabling new quantum optics and information science applications.

## Contribution

It presents a novel TESC technique that allows reversible, dynamic tuning of coupling between a plasmonic nano-cavity and single quantum dots at room temperature.

## Key findings

- Mode splitting > 160 meV observed
- Anticrossing over ~100 meV detuning range demonstrated
- Sub-nm precision control of mode volume achieved

## Abstract

Optical cavities can enhance and control light-matter interactions. This has recently been extended to the nanoscale, and with single emitter strong coupling regime even at room temperature using plasmonic nano-cavities with deep sub-diffraction-limited mode volumes. However, with emitters in static nano-cavities, this limits the ability to tune coupling strength or to couple different emitters to the same cavity. Here, we present tip-enhanced strong coupling (TESC) spectroscopy, imaging, and control. Based on a nano-cavity formed between a scanning plasmonic antenna-tip and the substrate, by reversibly and dynamically addressing single quantum dots (QDs) we observe mode splitting > 160 meV and anticrossing over a detuning range of ~100 meV, and with sub-nm precision control over the mode volume in the ~1000 nm^3 regime. Our approach, as a new paradigm of nano-cavity quantum-electrodynamics near-field microscopy to induce, probe, and control single-emitter plasmon hybrid quantum states, opens new pathways from opto-electronics to quantum information science.