Super- and subradiance of clock atoms in multimode optical waveguides

Abstract

The transversely confined propagating modes of an optical fiber mediate virtually infinite range energy exchanges among atoms placed within their field, which adds to the inherent free space dipole-dipole coupling. Typically, the single atom free space decay rate largely surpasses the emission rate into the guided fiber modes. However, scaling up the atom number as well as the system size amounts to entering a collective emission regime, where fiber-induced superradiant spontaneous emission dominates over free space decay. We numerically study this super-and subradiant decay of highly excited atomic states for one or several transverse fiber modes as present in hollow core fibers. As particular excitation scenarios we compare the decay of a totally inverted state to the case of π/2 pulses applied transversely or along the fiber axis as in standard Ramsey or Rabi interferometry. While a mean field approach fails to correctly describe the initiation of superradiance, a second-order approximation accounting for pairwise atom-atom quantum correlations generally proves sufficient to reliably describe superradiance of ensembles from two to a few hundred particles. In contrast, a full account of subradiance requires the inclusion of all higher order quantum correlations. Considering multiple guided modes introduces a natural effective cut-off for the interaction range emerging from the dephasing of different fiber contributions.

Protection of a qubit with a subradiance effect: Josephson quantum filter

“…Such prohibited decay of DQ originates in the subradiance effect [29][30][31]. This is understood most clearly in the case of l 1 = l 2 = 0.…”

Superradiance from lattice-confined atoms inside hollow core fibre

“…To understand the subtle mechanism behind the above experimental observations, we need to simulate the collective atom-light interplay under the experimental detection conditions. A similar in-fibre SR model has been studied in a recent theoretical work 39 , where the physical system is simplified and only the collective decay of excited atoms, rather than the photon emission, is focused on. Here, we model the practical physical system by employing Maxwell-Bloch equations (MBEs) 2 and derive the in-fibre light field directly.…”

“…We should point out that SR may start before p . The SR efficiency defined in the main text is then given by 39 = em ab ⁄ . Figure 6d of the main text plots the dependence of on the atomic number for the unexpanded cloud (i.e., = 0.87 mm), corresponding to Fig.…”

Quantum Borrmann effect for dissipation-immune photon-photon correlations

“…For example, long-living supercavity modes with Γ rad Γ 0 , inspired by the photonic bound states in continuum [7], have been recently realized for resonant dielectric nanoparticles [8]. Similar concepts to engineer subradiant modes apply in the quantum regime [9][10][11][12] as has been recently demonstrated for single-photon excitations of a superconducting qubit array coupled to a waveguide [13]. It is however much harder to suppress the nonradiative decay.…”