Credit: V. Boyer et al., JQI
A laser beam (marked as "probe") first passes through a mask that imprints a visual pattern. Along with a second laser beam (marked "pump"), it enters a cell containing a gas of rubidium atoms. Interactions between the rubidium gas and the beams produce an amplified version of the imprinted image as well as a second version of the image, rotated 180 degrees around the pump. The bottom panel shows, from left to right, an incoming probe beam imprinted with the letters "N" and "T," an outgoing probe beam with an amplified image, and an upside-down version of the letters. The middle image is "entangled" with the rightmost image; the images' changes over time are highly related to one another.