We consider a generalization of a recently proposed non-Hermitian model for resonant cavities coupled by a chiral mirror by taking into account number non-conservation and nonlinear interactions. We analyze non-Hermitian quantum dynamics of populations and entanglement of the cavity modes. We find that the interplay between initial coherence and non-Hermitian coupling leads to a counterintuitive population transfer. While an initially coherent cavity mode is depleted, the other empty cavity can be populated more than or less than the initially filled one. Moreover, the presence of nonlinearity yields population collapse and revival as well as bipartite entanglement of the cavity modes. In addition to coupled cavities, we point out that similar models can be found in -symmetric Bose-Hubbard dimers of Bose-Einstein condensates or in coupled soliton-plasmon waveguides. We specifically illustrate the quantum dynamics of populations and entanglement in a heuristic model that we propose for a soliton-plasmon system with soliton amplitude-dependent asymmetric interaction. Degree of asymmetry, nonlinearity and coherence are examined to control plasmon excitations and soliton-plasmon entanglement. Relations to -symmetric lasers and Jahn-Teller systems are pointed out.
We consider a generalization of a recently proposed non-Hermitian model for resonant cavities coupled by a chiral mirror by taking into account number non-conservation and nonlinear interactions. We analyze non-Hermitian quantum dynamics of populations and entanglement of the cavity modes. We find that the interplay between initial coherence and non-Hermitian coupling leads to a counterintuitive population transfer. While an initially coherent cavity mode is depleted, the other empty cavity can be populated more than or less than the initially filled one. Moreover, the presence of nonlinearity yields population collapse and revival as well as bipartite entanglement of the cavity modes. In addition to coupled cavities, we point out that similar models can be found in -symmetric Bose-Hubbard dimers of Bose-Einstein condensates or in coupled soliton-plasmon waveguides. We specifically illustrate the quantum dynamics of populations and entanglement in a heuristic model that we propose for a soliton-plasmon system with soliton amplitude-dependent asymmetric interaction. Degree of asymmetry, nonlinearity and coherence are examined to control plasmon excitations and soliton-plasmon entanglement. Relations to -symmetric lasers and Jahn-Teller systems are pointed out.
We investigate the Hermitian and the non-Hermitian dynamics of the mode entanglement in two identical optical cavities coupled by a chiral mirror. By employing the non-Hermitian quantum evolution, we calculate the logarithmic negativity measure of entanglement for initially Fock, coherent, and squeezed states, separately. We verify the nonconservation of mean spin for the initially coherent and squeezed states when the coupling is nonreciprocal and report the associated spin noise for each case. We examine the effects of nonconserved symmetries on the mode correlations and determine the degree of nonreciprocal coupling to establish robust quantum entanglement.
We investigate the dynamics of Einstein-Podolsky-Rosen steering in a soliplasmonic system where the asymmetrical coupling between linear solitons and nonlinear plasmons is controlled by the weak soliton amplitude. We employ non-Hermitian quantum dynamics to evaluate quantum steering witnesses for different coupling strengths. Quantum steering is examined for an initially Fock state and we briefly discuss Einstein-Podolsky-Rosen entanglement for initially coherent states. We numerically investigate the adjustability of the witnessing periods of quantum steering via tunable coupling strength of soliton-plasmon interaction and discuss the possibility of the nonlinear soliplasmonic systems as a robust platform for implementing one-sided quantum key distributions.
This thesis explores the non-equilibrium dynamics of photons in optical micro-resonators, focusing on how coherence and collective behavior emerge in driven and dissipative systems. Starting from a microscopic description, we derive a Lindblad master equation under the assumptions of Markovian dynamics and fast molecular relaxation. By employing a cumulant expansion technique, we obtain a closed set of coupled dynamical equations for relevant observables, providing a method to analyze the system dynamics. A central aspect of this work is the explicit incorporation of U(1) symmetry-breaking fields to describe photon coherence. This formulation allows us to establish a distinction between coherent (condensed) and incoherent (thermal) photon populations, even at the level of a single-mode resonator. Within this framework, we study the temporal stability of the condensate and show that its persistence is governed by a key mechanism, the presence of a so-called ghost attractor. Although this fixed point lies outside the physical parameter space, its basin of attraction strongly influences the system dynamics, which results in stabilizing the condensate over an extended period of time before it eventually decays to zero. Additionally, we investigate the stability of the system by analyzing fluctuations around its fixed points. This analysis reveals the presence of exceptional points in the parameter space, signaling non-Hermitian phase transitions. These exceptional points separate the dynamics into two qualitatively different dynamical regimes, namely, a weakly-damped oscillatory regime, and a purely dissipative regime with bi-exponential decay. Finally, we investigate the possibility of generating quantum correlations and entanglement in a system of two coupled micro-resonators. Despite the presence of coherent dynamics and inter-cavity coupling, our results show that the photon states remain separable throughout the time evolution. This conclusion is supported by the evaluation of continuous-variable entanglement criteria for Gaussian states, which naturally arise within the cumulant expansion framework.
In this paper, we explore the atomic population inversion and entanglement dynamics of a quantum system consisting of three identical two-level atoms interacting with a single-mode cavity field. The cavity is surrounded by a Kerr medium exhibiting f-deformed Kerr nonlinearity, and we consider a degenerate multi-photon transition in the nonlinear regime. The study systematically analyzes the effects of intensity-dependent coupling, detuning, Kerr nonlinearity, f-deformed Kerr nonlinearity, and multi-photon transition on the nonclassical properties of the system. Our results show that the Kerr and f-deformed Kerr nonlinearities significantly influence the atomic inversion dynamics, leading to phenomena such as collapse and revival, with distinct behaviors observed under varying detuning parameters. Furthermore, entanglement dynamics between the atoms and cavity mode are enhanced under intensity-dependent coupling and nonlinearity. The detuning parameter generally reduces entanglement but has a less pronounced effect in the two-photon transition case, where entanglement is notably enhanced. The study provides valuable insights into controlling quantum correlations in multi-atom systems, with potential applications in quantum information processing, computing, and communication.
Dynamics of entanglement due to intensity-dependent interaction between a two-level atom and a single-mode electromagnetic field in a Kerr medium is studied. The form of the interaction is such that the Hamiltonian evolution is exactly solvable. The Hamiltonian is shown to be a deformed Jaynes-Cummings model admitting a closed, symmetric algebra. Dynamics of population inversion and atom-field entanglement are studied taking the initial state of the field to be either a coherent state or a squeezed vacuum. Analysis is extended to the case of a two-mode cavity field interacting with a two-level atom. For the two-mode case, the initial field is a pair coherent state or a two-mode squeezed vacuum. Effects due to nonlinearity, intensity-dependent interaction and detuning on the dynamics are discussed and compared with those of the single-mode case.
The transition dynamics of photons between an optical soliton in a nonlinear dielectric waveguide and a spatially coupled surface-plasmon excitation on a parallel flat metal surface can be formulated in analogy to that of a Josephson junction of two-level (double-well) Bose-Einstein condensates, albeit with a nonlinear coupling that inherently depends on the population imbalance of the levels. The present work demonstrates that asymmetric Rosen-Zener--like transitions can be obtained through this optical Josephson junction, by turning on and off the coupling across a hyperbolically varying separation between the soliton and the surface-plasmon. The transitions can generate full population transfer, population splitting, or merging between the quasistationary initial and final states, which are defined by a fixed population imbalance in the decoupled limit. Transitions from a pure soliton or pure surface-plasmon initial state are found to be robust against the relative phase, whereas the transitions from an initial state with mixed population depend strongly on the relative phase. The soliton--surface-plasmon system also bears similarities to the spatially coupled optical waveguides which are introduced further as the classical analogs of the spatial adiabatic passage and stimulated Raman adiabatic passage mechanisms in quantum and atom optics.