An ordinary flash drive stores bits in electron traps, but you can only read them through a separate wire and amplifier. In the new development, the same piece of the semimetal tellurium plays both the role of storage and the light bulb. When a short electrical pulse is applied, electrons get stuck in a trap layer, and the crystal itself begins to emit infrared light. The brightness of this light shows which of the 16 levels is recorded.
The writing speed is nanoseconds, meaning you can save a billion values in one second. Moreover, the data does not disappear when power is turned off: electrons remain in traps like water in a sponge. Light with a wavelength of 3.4 microns lies in the mid-infrared range, which is used by thermal imagers and gas sensors. This means such a device can be directly connected to optical sensors without converters.
The authors tested the memory in a neural network: it recognized clothing in images from the Fashion-MNIST set with high accuracy. This is not a replacement for ordinary memory, but a bridge between electrical circuits and optical channels. The computer of the future will be able to store, compute, and sense in a single crystal that glows in time with its thoughts.
Infrared light with a wavelength of 3.4 microns is invisible to the eye, but thermal imagers pick it up perfectly: it is in this range that the heat of the human body 'glows'.