Multiphoton Quantum Rabi Oscillations in Waveguide QED

Cavity QED and chip-scale nanophotonics constitute the keystones to the future of quantum information processing and communication. One of the foremost processes underpinning quantum photonic technologies is the phenomenon of Rabi oscillations wherein a qubit is irradiated by a coherent light source. In contrast to this conventional setting, in this talk, we expound on the more general case where the optical excitation is the multiphoton Fock state which is a fundamental building block for the photonic Hilbert space. By employing the real-space approach in waveguide QED, we analytically explore the scattering dynamics of the photonic Fock state as it interfaces with a two-level emitter. Our analysis extends the results on single-mode Rabi oscillations pertinent to cavity QED, to the paradigmatic, multimode, waveguide-QED models where flying photons are the essential information carriers. The temporal evolution of the qubit excitation in our configuration shows canonical correspondences as well as some critical differences with the single-mode, cavity-QED result. Specifically, in the regime of large detunings, the qubit exhibits Rabi-like oscillatory dynamics akin to the single-mode case. Contrastingly, in the opposite regime of very low detunings, spontaneous emission from the qubit gains prominence and can quickly stifle any oscillatory signatures. Our findings should be relevant to future Fock-state-based quantum computing and associated waveguide-integrated photonic technologies.