M V S de Paula | Searcharxiv

arXiv2025

Comparison of Quantum and Semiclassical Rabi models near multiphoton resonances in the presence of parametric modulation

We compare the semiclassical and quantum predictions for the unitary dynamics of a two-level atom interacting with a single-mode electromagnetic field in the presence of parametric modulation of the atomic parameters, in the regime of multiphoton atom-field resonances. We derive approximate analytic solutions for the semiclassical Rabi model when the atomic transition frequency and the atom-field coupling strength undergo harmonic external modulations. These solutions are compared to the predictions of the quantum Rabi model, which is solved numerically for the initial coherent state with a large average photon number, of the order of $10^4$, in the regime of three-photon resonance. We show that for initial times and sufficiently intense coherent state the semiclassical dynamics agrees quite well with the quantum one, although for large times it inevitably fails due to the lack of the collapse-revival behavior. Furthermore, we describe how the field state is modified throughout the evolution, presenting numeric results for the average photon number, entropies (related to the atom-field entanglement) and other quantities that characterize the photon number statistics of the electromagnetic field.

quant-ph↗

arXiv2022

Generation of photons from vacuum in cavity via time-modulation of a qubit invisible to the field

We propose a scheme for generation of photons from vacuum due to time-modulation of a quantum system coupled indirectly to the cavity field through some ancilla quantum subsystem. We consider the simplest case when the modulation is applied to an artificial 2-level atom (we call t-qubit), while the ancilla is a stationary qubit coupled via the dipole interaction both to the cavity and t-qubit. We find that tripartite entangled states with a small number of photons can be generated from the system ground state under resonant modulations, even when the t-qubit is far detuned from both the ancilla and the cavity, provided its bare and modulation frequencies are properly adjusted as function of other system parameters. We attest our approximate analytic results by numeric simulations and show that photon generation from vacuum persists in the presence of common dissipation mechanisms.

quant-ph↗