'Waveguide quantum optomechanics: parity-time...'
'Waveguide quantum optomechanics: parity-time phase transitions in the ultrastrong coupling regime'
Abstract: We show that the physics of waveguide quantum electrodynamics (QED) can be substantially enriched by inclusion the qubit mechanical motion. Specifically, considering the simplest set-up of a pair of harmonically trapped qubits over an optical waveguide, we reveal that the system enables the ultrastrong coupling regime of the quantum optomechanical interaction. Moreover, the combination of the inherent open nature of the system and the strong optomechanical coupling, leads to the emergence of the parity-time phase transitions, an unconventional phenomena in the purely quantum systems without artificially engineered gain and loss. Finally, we establish a link between our results and those of the classical waveguide optomechanics and discuss the emergent observable effects in the state-of-the-art waveguide QED set ups. Our findings shed light on the plethora of the new physical phenomena in the optomechanics of waveguide QED and could be harnessed in the emerging quantum technologies.