[Note: This item comes from reader Randall Head. DLH]
Storing data in a single atom proved possible by IBM researchers
By Devin Coldewey
Mar 8 2017
The fundamental components of computers are becoming small enough that they are pressing against the boundaries of the familiar world of Newtonian physics. And nowhere is the scale and precision of operation on better display than in hard disk drives, where a trillion bits may fit in a square inch. But IBM has outdone them all by reading and writing data to a single atom.
This advance may be more symbolic than practical right now, but merely showing a working example of atomic data storage, orders of magnitude smaller than state of the art techniques, is practically science fiction.
Atoms, it may not surprise you to hear, are pretty much the smallest unit of matter that we can manipulate reliably and expect to stay still. There are interesting experiments with entangling photons, but they’re squirrelly customers. Better to stick to things that don’t fire off at the speed of light if you lose your grip for a second. And a previous atomic storage technique doesn’t actually store data in the atom, but moves them around to form readable patterns (still cool).
This means that imbuing individual atoms with a 0 or 1 is the next major step forward and the next major barrier in storing data digitally, both increasing capacity by orders of magnitude and presenting a brand new challenge to engineers and physicists. IBM’s experiment, published today in Nature, takes true atomic storage from theory to reality.
It works like this: A single Holmium atom (a large one with many unpaired electrons) is set on a bed of magnesium oxide. In this configuration, the atom has what’s called magnetic bistability: It has two stable magnetic states with different spins (just go with it).
The researchers use a scanning tunneling microscope (also invented at IBM, in the 1980s) to apply about 150 millivolts at 10 microamps to the atom — it doesn’t sound like a lot, but at that scale, it’s like a lightning strike. This huge influx of electrons causes the Holmium atom to switch its magnetic spin state. Because the two states have different conductivity profiles, the STM tip can detect which state the atom is in by applying a lower voltage (about 75 millivolts) and sensing its resistance.
In order to be absolutely sure the atom was changing its magnetic state and this wasn’t just some interference or effect from the STM’s electric storm, the researchers set an iron atom down nearby. This atom is affected by its magnetic neighborhood, and acted differently when probed while the Holmium atom was in its different states. This proves that the experiment truly creates a lasting, stored magnetic state in a single atom that can be detected indirectly.
And there you have it: a single atom used to store what amounts to a 0 or a 1. The experimenters made two of them and zapped them independently to form the four binary combinations (00,01,10,11) that two such nodes can form. The abstract summarizes: