2019/03/25 by Petra Ruth Kaprálová-Žďánská, Kapralova-Zdanska, Petra Ruth, Milan Šindelka +3
Physics and Astronomy · #FOS: Physical sciences #Laser-Matter Interactions and Applications #Quantum Physics (quant-ph) #Quantum optics and atomic interactions #Spectroscopy and Quantum Chemical Studies
paper · pdf · doi:10.48550/arxiv.1903.10383
openalex publication_date 2019/03/25 · openalex created_date 2022/07/29 · openalex updated_date 2026/07/28
We study theoretically the population transfer in two-level atoms driven by chirped lasers. It is known that in the Hermitian case, the rapid adiabatic passage (RAP) is stable for an above-critical chirp below which the final populations of states Rabi oscillate with varying laser power. We show that if the excited state is represented by a resonance, the separatrix marking this critical phenomenon in the space of the laser pulse parameters emanates from an exceptional point (EP) -- a non-Hermitian singularity formed in the atomic system by the fast laser field oscillations and encircled due to slow variations of the laser pulse envelope and instantaneous frequency. This critical phenomenon is neatly understood via extending the "slow" time variable into the complex plane, uncovering a set of branch points which encode non-adiabatic dynamics, where the switch between RAP and Rabi oscillations is triggered by a coalescence of two such branch points. We assert that the intriguing interrelation between the two different singularities -- the EP and the branch point coalescence in complex time plane -- can motivate feasible experiments involving laser driven atoms.