"Scientists at the Joint Quantum Institute have stored not one but two letters of the alphabet in a tiny cell filled with rubidium (Rb) atoms which are tailored to absorb and later re-emit messages on demand. This is the first time two images have simultaneously been reliably stored in a non-solid medium and then played back. In effect, this is the first stored and replayed atomic movie. Because the JQI researchers are able to store and replay two separate images, or "frames," a few micro-seconds apart, the whole sequence can qualify as a feat of cinematography. (...) The atomic storage medium is a narrow cell some 20 centimeters long, which seems pretty large for a quantum device. That's how much room is needed to accommodate a quantum process called gradient echo memory (GEM). (...) " - Amira

"The image is stored in this extended way, by being absorbed in atoms at any one particular place in the cell, depending on whether those atoms are exposed to three carefully tailored fields: the electric field of the signal light, the electric field of another "control" laser pulse, and a magnetic field (adjusted to be different along the length of the cell) which makes the Rb atoms (each behaving like a magnet itself) precess about. When the image is absorbed into the atoms in the cell, the control beam is turned off. Because this process requires the simultaneous action of two particular photons---one putting the atom in an excited state, the other sending it back down to a slightly different ground state---it cannot easily be undone by atoms subsequently randomly emitting light and returning to the original ground state. That's how the image is stored. Image readout occurs in a sort of reverse process. The magnetic field is flipped to a contrary orientation, the control beam turned back on, and the atoms start to precess in the opposite direction. Eventually those atoms reemit light, thus reconstituting the image pulse, which proceeds on its way out of the cell." - Amira