Superfast, low-energy computing using light pulses

An international team of scientists has created superfast data processing using light pulses instead of electricity, using the power of magnets to record computer data. Published in the journal Nature, the work solves the dilemma of how to create faster data processing speeds without the accompanying high energy costs.

Today’s data centre servers consume 2–5% of global electricity consumption, producing heat which in turn requires more power to cool the servers. The problem is so acute that Microsoft has even submerged hundreds of its data centre services in the ocean in an effort to keep them cool and cut costs.

Most data is encoded as binary information (0 or 1 respectively) through the orientation of tiny magnets, called spins, in magnetic hard drives. The magnetic read/write head is used to set or retrieve information using electrical currents, which dissipate huge amounts of energy.

Researchers have now solved this problem by replacing electricity with extremely short pulses of light — the duration of one trillionth of a second — concentrated by special antennas on top of a magnet. The method is superfast and so energy efficient that the temperature of the magnet does not increase at all.

The team demonstrated their new method by pulsing a magnet with ultrashort light bursts (the duration of a millionth of a millionth of a second) at frequencies in the far infrared, the so-called terahertz spectral range. Even the strongest existing sources of terahertz light could not provide strong enough pulses to switch the orientation of a magnet — until the team discovered and utilised the efficient interaction mechanism of coupling between spins and terahertz electric field.

The scientists then developed and fabricated a very small antenna on top of the magnet to concentrate and thereby enhance the electric field of light. This strong local electric field was sufficient to navigate the magnetisation of the magnet to its new orientation in just one trillionth of a second. Furthermore, the temperature of the magnet did not increase at all as this process requires energy of only one quantum of the terahertz light — a photon — per spin.

“The record-low energy loss makes this approach scalable,” said Dr Rostislav Mikhaylovskiy, formerly at Radboud University and now at Lancaster University.

“Future storage devices would also exploit the excellent spatial definition of antenna structures enabling practical magnetic memories with simultaneously maximal energy efficiency and speed.”

Dr Mikhaylovskiy plans to carry out further research using the new ultrafast laser at Lancaster University together with accelerators at the Cockroft Institute, which are able to generate intense pulses of light to allow switching magnets and to determine the practical and fundamental speed and energy limits of magnetic recording.

Image caption: Using ultrashort pulses of light enables extremely economical switching of a magnet from one stable orientation (red arrow) to another (white arrow). This concept enables ultrafast information storage with unprecedented energy efficiency. Image© Brad Baxley (parttowhole.com).

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