Surface-plasmon based dispersive detection and spectroscopy of ultracold atoms

TL;DR

This paper introduces a plasmonic detection method for ultracold atoms near a gold surface, enabling nondestructive, high-resolution spectroscopy and quantum nondemolition measurements.

Contribution

It presents a novel surface plasmon-based dispersive detection technique for ultracold atoms with single-atom resolution and nondestructive capabilities.

Findings

Achieved a sensitivity of 30 atoms.

Demonstrated dispersive imaging of atom clouds.

Enabled quantum nondemolition measurements.

Abstract

The paper reports on the optical detection and spectroscopy of ultracold atoms near a gold surface. A probe light field is used to excite surface plasmon polaritons. The refractive index of the atomic gas shifts the plasmon resonance and changes the reflected light power. Thus, the sensitivity of the detection is plasmonically enhanced. Absorption of photons from the evanescent wave is avoided by detuning the laser from atomic resonance which makes the detection scheme potentially nondestructive. The spectrum of the signal is determined by a Fano resonance. We show that atoms can be detected nondestructively with single atom resolution for typical parameters in cold atom experiments. Thus, the method is suitable for quantum nondemolition measurements of matter wave amplitudes. Experimentally, we measure a technically-limited sensitivity of 30 atoms and extend the detection scheme to dispersively image the atom cloud near the surface.