Memory from a Cesium Vapor express
A beam of light enters a glass cell filled with cesium vapor and changes the internal state of the atoms: this is how information is recorded. A moment later, another beam reads it out by how the atoms absorb light. It's not a hard drive, but rather a notebook that turns its own pages.
Eight such "pages" are created by an acousto-optic deflector — a device that bends light with sound. Each page stores up to 3.8 bits. The whole setup works as a reservoir computer: data gets mixed in the atomic cloud, and the system finds patterns on its own. On the XOR test (the logical "exclusive or" operation), the computer made errors in only 2% of cases.
The main result is showing for the first time that optical memory from free atomic vapor can serve as the foundation for computing. Next steps are to speed up writing and extend data lifetime, so such a computer can handle long signals, like speech or video.
Cesium is a metal that melts in your hand: its melting point is just 28.5°C. In the cell, it exists as vapor at room temperature.
In Greg Egan's novel "Permutation City," a mind is stored in a cloud of quantum states, an idea that echoes storing data in atomic vapor.