Direct Measurements of Collisional Dynamics in Cold Atom Triads

The introduction of optical tweezers for trapping atoms has opened remarkable opportunities for manipulating few-body systems. Here, we present the first bottom-up assembly of atom triads. We directly observe atom loss through inelastic collisions at the single event level, overcoming the substantial challenge in many-atom experiments of distinguishing one-, two-, and three-particle processes. We measure a strong suppression of three-body loss, which is not fully explained by the presently availably theory for three-body processes. The suppression of losses could indicate the presence of local anticorrelations due to the interplay of attractive short range interactions and low dimensional confinement. Our methodology opens a promising pathway in experimental few-body dynamics.

Figure 1

Experimental procedure for directly observing cold atom collisions. We isolate three ${}^{85}\mathrm{Rb}$ atoms in separate optical tweezers and confirm their presence through fluorescence imaging. A merge and compression stage allows the atoms to interact. Readout: number of photon occurrences for zero (blue), one (yellow), two (green), and three (red) atoms in the tweezer.

Figure 2

Measurements of loss dynamics in triads (a) and dyads (b). Measured probability for the remaining atom number being as follows: three, red diamond; two, green circle; one, yellow star; zero, blue squares. Solid lines signify a fit to the data with proper ${\mathrm{\Gamma }}_j$ for triads [Eq. (2)] and dyads.

Figure 3

Comparison of experimentally measured values of the three-body loss rate ${\mathrm{\Gamma }}_3$ (purple, solid) with different theoretical models. Blue, dashed: a thermal gas without interaction-induced correlations. Green, dash-dotted: super-Tonks-Girardeau correlations with an integrated thermal density. Red, dotted: assumes a 1D gas with no occupation of transverse excited modes.

Figure 4

Measured decay rate using ${\tilde{\mathrm{\Gamma }}}_2$ for triads (red square) and ${\mathrm{\Gamma }}_2$ for dyads (blue circle) as a function of trap frequency. Inset. Illustration of off-resonant photoassociation coupling.