Tiny magnetic vortices — called skyrmions — in two-dimensional materials can produce completely random sequences of numbers. These are needed for cybersecurity, scientific simulation experiments and computer games.
For example, completely random number sequences are used to encrypt online messages. This way you can be sure that a financial transaction can only be viewed by your bank. “If the numbers generated are not really random, it may be possible for someone to find patterns in the numbers,” physicist emails Kang Wang from Brown University in the US. ‘Then unauthorized organizations can gain access to your data.’
Creating truly random sequences of numbers is difficult for computers. They now usually use algorithms that work according to strict, deterministic rules and are therefore not ‘really’ random. For some applications this is not a problem. But in bank transactions and online poker, you don’t want the random sequence of numbers to be traceable.
ALSO READ
Hypersonic Warfare
skyrmions
Completely random numbers for computers are produced from unpredictable processes, such as fluctuations in the ambient temperature or atmosphere. There are even companies that base their random number sequences on the movements in a lava lamp†
Wang’s group has now developed a new way to produce millions of random digits per second. To do this, the physicists use the random behavior of skyrmions: small magnetic phenomena that can arise in certain superflat materials. Scientists have been interested in skyrmions for some time because of their potential application in the next generation of computers.
In flat, two-dimensional materials, skyrmions can be formed by the magnetic moment or the ‘spin’ of the electrons present. You can imagine that spider as a tiny magnet with a north and a south pole. Like a compass needle, the spider can point in different directions.
By applying an electric or magnetic field, some of these electron spins change direction. This ensures that the electrons around their spin also start spinning. This creates a kind of magnetic vortex of electron spins in the material. That’s called a skyrmion.
Random wobbling vortices
Skyrmions are about a micrometer in size (one thousandth of a millimeter). They zoom through the material, but are quite stable, so they don’t just disappear.
To use skyrmions, the researchers secure them. To do this, they make small ‘flaws’ in the material. Those flaws consist of atoms that do not occur in the rest of the material. The flaws grab the skyrmions on one side and hold them in place. They then no longer move through the material, but the skyrmions do not sit still. They occasionally get bigger and then smaller again.
‘This jumping back and forth of the size depends on small temperature fluctuations,’ says Wang. “That makes it completely random.”
The researchers measure the changes in the size of the skyrmion by running a current through the material. That electric current reacts to the magnetic spins. They then convert the measured current fluctuations into a series of random numbers.
By further optimizing their setup, the researchers believe they can deliver millions of random numbers per second. “We expect this technique to fit in a small box or even on a computer chip,” Wang says. ‘That way it can easily be used wherever random numbers are needed.’