Waveguide quantum electrodynamics: Controllable channel from quantum interference
Qiong Li, Lan Zhou, C. P. Sun · Physical Review A · 2014
We study a waveguide QED system with a rectangular waveguide and a two-level system inside, where the transverse magnetic TM${}_{mn}$ modes define the quantum channels of guided photons. It is discovered that the loss of photons from the TM${}_{11}$ channel into the others can be overcome by replacing it with a certain coherent superposition of TM${}_{mn}$ channels, which is named the controllable channel (CC), as the photons in the CC can be perfectly reflected or transmitted by the two-level system and never lost into the other channels. A dark state emerges when the photon is incident from one of the scattering-free channels orthogonal to the CC. The underlying physics mechanism is the multichannel interference associated with Fano resonance.