Thilagaraj Ravi

In atom-based quantum technologies, motion is seen as a nuisance. The tiniest atomic jiggle or vibration can scramble the delicate quantum information stored in internal states such as the atom’s electronic or nuclear spin, especially during operations when those states get read out or changed. Now, however, Manuel Endres and colleagues at the California Institute of Technology (Caltech), US, have found a way to turn this long-standing nuisance into a useful feature.

The well-known sub-Doppler polarization gradient cooling in a type-I transition (Fe=Fg+1) is caused by red-detuned lasers. On the other hand, in a type-II transition (Fe≤Fg), sub-Doppler cooling takes place through blue-detuned lasers. This opposite behavior for the two types of transitions is due to spontaneously transferred coherence (STC). In the absence of STC, both types of transitions show blue-detuned cooling.

We report continuous loading of Rb87 atoms in a magneto-optical trap (MOT) at narrow linewidth, 420-nm 5S1/2, F=2→6P3/2, F=3 blue transition (blue MOT). Continuous loading of the blue MOT is achieved by superimposing the blue laser beam inside a hollow core of infrared (IR) laser beam driving the broad 5S1/2, F=2→5P3/2, F=3 transition at 780 nm. We typically load ∼108 atoms in the blue MOT in 2.5 s.