Non-destructive detection of ions using atom-cavity collective strong coupling

Abstract

We present a technique, based on atoms coupled to an optical cavity, for nondestructive detection of trapped ions. We demonstrate the vacuum-Rabi splitting (VRS), arising from collective strong coupling of ultracold Rb atoms and a cavity, to change in the presence of trapped Rb+ ions. The Rb+ ions are optically dark and the Rb atoms are prepared in a dark magneto-optical trap. The VRS is measured on an optically open transition of the initially dark Rb atoms. The measurement itself is fast, nondestructive, and has sufficient fidelity to permit the measurement of the atomic-state-selective ion-atom collision rate. This demonstration illustrates a method based on atom-cavity coupling to measure two-particle interactions generically and nondestructively.