Think your computer is pretty slow? Relax, in the future, your hard disk could be able to run ten thousand times faster.
This will be made possible, according to a recent experiment performed at Rome's La Sapienza University - in collaboration with the Polytechnic of Milan and the Radbound University of Nijmegen - by going beyond classical physics and account for quantum phenomena below the nanosecond timescale.
It's quite complicated and a bit technical, but let's try to make it as clear as possible. Right now, data recording on magnetic support is based on the ability to modify magnetic properties of material. This is normally achieved by imposing a well-defined magnetic direction to some portions of the medium, the so called “Weiss domains”.
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To robustly engrave a single bit, in fact, a relatively large number of extended domains have to be used, to secure the information against random thermal fluctuations which may accidentally erase the data, and this requirement sets a limit to the speed that it's possible to achieve.
That's part of the reason why, in recent years, a lot of effort has been devoted to investigate magnetic phenomena below the nanosecond timescale: an entirely new field of research, named “Femtomagnetism” was born, focused on the study of the so called 'exchange interaction', which governs magnetisms on such ultrafast time scales.
The exchange interaction plays a pivotal role in defining the magnetic behavior of materials. "Basically, a single atom often possesses an intrinsic magnetic field, which can be visualized as a magnetic needle," La Sapienza's Tullio Scopigno who coordinated the research, tells me.
"The relative orientation of all the needles inside a material affects the distribution of its electric charge, and therefore provides a contribution to the electrostatic energy, called exchange energy. The origin of this mechanism cannot be explained by classical physics, since it is related to the so-called Pauli exclusion principle, one of the foundations of quantum mechanics," he adds.
To increase the exchange energy without necessarily altering the magnetic structure of the material, researchers have been using laser pulses to directly modify the amount of the interaction among the atoms.
Remarkably, this happens in a time interval well below the nanosecond, as the material response is almost entirely exhausted within the duration of the laser pulse, less than 100 femtoseconds in the experiment (1 femtosecond is one millionth of one billionth of a second ).
The result therefore demonstrates a new route to circumvent the hindrances of the current magnetic storage technology, to reach writing and reading speeds up to ten thousand times faster than those currently available.
"The idea of using lasers is not new. DVDs are written in fact using a laser. But in that case, micro-engravings have to be created in the magnetic support, a process which is relatively 'slow'. Our method shows that it's possible to use ultra-fast laser pulses, to read and write data without causing the thermal effects which would inevitably slow down the process," Scopigno says.
At the moment it's all very theoretical, a "proof of principle" obtained in a lab, making use of expensive and relatively bulky lasers, but if the past is any indication, miniaturization will follow and these kind of applications will sooner or later find their way to the market, as it has already happened with the ultra-compact lasers with which we now read DVDs.
