Continuous control of the coupling constant in an atom-cavity system by using elliptic polarization and magnetic sublevels

Abstract

Atom-cavity coupling constant is a key parameter in cavity quantum electrodynamics for describing the interaction between an atom and a quantized electromagnetic field in a cavity. This paper reports a novel way to tune the coupling constant continuously by inducing an averaging of the atomic dipole moment over degenerate magnetic sublevels with elliptic polarization of the cavity field. We present an analytic solution of the stationary-state density matrix for this system with consideration of F -> F +1 hyperfine transition under a weak excitation condition. We rigorously show that the stationary-state emission spectra of this system can be approximated by that of a non-degenerate two-level atom with an effective coupling constant as a function of the elliptic angle of the cavity field only. A precise condition for this approximation is derived and its physical meaning is interpreted in terms of a population-averaged transition strength and its variance. Our results can be used to control the coupling constant in cavity quantum electrodynamics experiments with a degenerate two-level atom with magnetic sublevels. Possible applications of our results are discussed.

Deterministic generation of multiparticle entanglement in a coupled cavity-fiber system

“…Generating multiparticle entangled states has been proposed or even experimentally demonstrated in different physical systems, such as atomic ensembles in free space [6], trapped ions [7,8], cold atoms in optical lattice [9], and cavity QED [10,11]. Among various excellent systems, cavity QED [10,11] offers one of the most promising and qualified candidates for quantum state engineering and quantum information processing [12,13,14,15,16,17,18], particularly, for applications in quantum networking [19], quantum communication, and distributed quantum computation, since atoms trapped in optical cavities are the natural candidates for quantum nodes, and these nodes can be connected by quantum channels such as optical fibers [12,19]. Quantum information is generated, processed and stored locally in each node, which is connected by optical fibers, and is transferred between different nodes via photons through the fibers.…”