We study the algebraic structure of the one-dimensional Dirac oscillator by extending the concept of spin symmetry to a noncommutative case. An SO(4) algebra is found connecting the eigenstates of the Dirac oscillator, in which the two elements of Cartan subalgebra are conserved quantities. Similar results are obtained in the Jaynes--Cummings model.
We present evidence of metastable rare quantum-fluctuation switching for the driven dissipative Jaynes-Cummings oscillator coupled to a zero-temperature bath in the strongly dispersive regime. We show that single-atom complex amplitude bistability is accompanied by the appearance of a low-amplitude long-lived transient state, hereinafter called `dark state, having a distribution with quasi-Poissonian statistics both for the coupled qubit and cavity mode. We find that the dark state is linked to a spontaneous flipping of the qubit state, detuning the cavity to a low-photon response. The appearance of the dark state is correlated with the participation of the two metastable states in the dispersive bistability, as evidenced by the solution of the Master Equation and single quantum trajectories.
We study the analytic structure for the eigenvalues of the one-dimensional Dirac oscillator, by analytically continuing its frequency on the complex plane. A twofold Riemann surface is found, connecting the two states of a pair of particle and antiparticle. One can, at least in principle, accomplish the transition from a positive energy state to its antiparticle state by moving the frequency continuously on the complex plane, without changing the Hamiltonian after transition. This result provides a visual explanation for the absence of a negative energy state with the quantum number n=0.
The theory of non-Hermitian systems and the theory of quantum deformations have attracted a great deal of attention in the last decades. In general, non-Hermitian Hamiltonians are constructed by a textit{ad hoc} manner. Here, we study the (2+1) Dirac oscillator and show that in the context of the $kappa$--deformed Poincare-Hopf algebra its Hamiltonian is non-Hermitian but having real eigenvalues. The non-Hermiticity steams from the $kappa$-deformed algebra. From the mapping in [Bermudez textit{et al.}, Phys. Rev. A textbf{76}, 041801(R) 2007], we propose the $kappa$-JC and $kappa$--AJC models, which describe an interaction between a two-level system with a quantized mode of an optical cavity in the $kappa$--deformed context. We find that the $kappa$--deformation modifies the textit{Zitterbewegung} frequencies and the collapse and revival of quantum oscillations. In particular, the total angular momentum in the $z$--direction is not conserved anymore, as a direct consequence of the deformation.
We study multiphoton blockade and photon-induced tunneling effects in the two-photon Jaynes-Cummings model, where a single-mode cavity field and a two-level atom are coupled via a two-photon interaction. We consider both the cavity-field-driving and atom-driving cases, and find that single-photon blockade and photon-induced tunneling effects can be observed when the cavity mode is driven, while the two-photon blockade effect appears when the atom is driven. For the atom-driving case (the two-photon transition process), we present a criterion of the correlation functions for the multiphoton blockade effect. Specifically, we show that quantum interference can enhance the photon blockade effect in the single-photon cavity-field-driving case. Our results are confirmed by analytically and numerically calculating the correlation function of the cavity-field mode. Our work has potential applications in quantum information processing and paves the way for the study of multiphoton quantum coherent devices.
We present a propagator formalism to investigate the scattering of photons by a cavity QED system that consists of a single two-level atom dressed by a leaky optical cavity field. We establish a diagrammatic method to construct the propagator analytically. This allows us to determine the quantum state of the scattered photons for an arbitrary incident photon packet. As an application, we explicitly solve the problem of a single-photon packet scattered by an initially excited atom.