Abstract In this paper, the entanglement dynamics of different subsystems such as atom–atom, atom–field and field–field with radiation field in squeezed coherent thermal states for the intensity-dependent double Jaynes–Cummings model (DJCM) and DJCM are investigated. The effects of squeezed and thermal photons on entanglement are examined, revealing their complementary roles in shaping the entanglement behavior in both models. One of the main features of the DJCM is the observation of entanglement sudden death for every subsystem. The effects of various interactions such as Ising interaction, single photon exchange interaction and dipole–dipole interaction (DDI) on entanglement dynamics are studied. The effects of detuning, Kerr-nonlinearity on the entanglement dynamics are investigated for every subsystem. It is noticed that proper choice of the interaction parameters associated with photon exchange interaction, DDI, detuning and Kerr-nonlinearity effectively remove entanglement deaths from the dynamics.
We examine the interaction of thermal light with matter with emphasis on two aspects that have not been considered before. By employing a fully quantized Jaynes-Cummings--type interaction model on a
V-type three-level system, we show that multimode thermal light induces coherence in the excited material states. This is in contrast to previous studies that suggest thermal light cannot induce coherence in material systems. We also show that the ratio between the field detuning and the interaction constant has a significant influence on the characteristic time-dependent dynamics. In particular, for some ratio regimes, the thermal light induces dynamics with a ``coherentlike'' collapse and revivals pattern rather than the familiar pattern. We then extend the Jaynes-Cummings model to a two-state Born-Oppenheimer potential energy surface molecular system where the internal vibrational degrees of freedom are fully taken into account. The matter-field bipartite system is represented, and propagated, in the full electronic bond-coordinate Fock product space. We show that single-mode thermal light induces extensive excited-state vibrational coherence in the molecule that, when observed in coordinate space, exhibits wave-packet-like dynamics. The molecular Jaynes-Cummings model we propose is useful for cavity molecular dynamics simulations.
We study the thermal effects of the multiphoton Jaynes-Cummings model (JCM) using a thermofield dynamics (TFD) method. Letting the initial state of the whole system for the multiphoton JCM be a product of the ground state of an atom and a coherent state of a cavity field at finite temperature, we compute its time evolution. We evaluate a period of the collapse and revival of the Rabi oscillations and the relative entropy of coherence of the atom up to the second-order perturbation of the low-temperature expansion. We show that an intuitive estimation of the period matches the result of the perturbation theory of TFD well. In particular, we see that the period of the two-photon JCM hardly depends on the amplitude of the coherent state of the cavity field or the temperature. Numerical calculations suggest that the relative entropy of coherence of the two-photon JCM does not decay even for nonzero-temperature cases as time proceeds. By contrast, the relative entropies of coherence for single-, three-, and four-photon JCMs decay as time proceeds for zero- and finite-temperature cases.