Strong coupling cavity QED using rare-earth-ion dopants in monolithic resonators: what you can do with a weak oscillator

TL;DR

This paper explores the feasibility of achieving strong and weak coupling regimes in cavity QED using rare-earth-ion doped monolithic resonators, highlighting challenges and potential quantum information applications.

Contribution

It analyzes the conditions under which strong and weak coupling regimes can be realized with rare-earth ions in monolithic resonators, proposing methods for quantum state transfer and detection.

Findings

Strong coupling is difficult due to weak oscillator strengths.

Weak coupling ('bad cavity') regime is more achievable.

Quantum state transfer and phase shifts are possible in the bad cavity regime.

Abstract

We investigate the possibility of achieving the strong coupling regime of cavity quantum electrodynamics using rare earth ions as impurities in monolithic optical resonators. We conclude that due to the weak oscillator strengths of the rare earths, it may be possible but difficult, to reach the regime where the single photon Rabi frequency is large compared to both the cavity and atom decay rates. However reaching the regime where the saturation photon and atom numbers are less than one should be much more achievable. We show that in this `bad cavity' regime, transfer of quantum states and an optical phase shift conditional on the state of the atom is still possible, and suggest a method for coherent detection of single dopants.