Using a simple laser, the team created the fastest random number generator ever built. Uses fluctuations in light intensity to create randomness – a desirable resource for data coding and scientific simulations. As a physicist and a fellow reporting for Science. Upgrading can result in devices small enough to fit into a single computer chip.
True randomness is difficult to achieve. Algorithms in traditional computers can generate sequences of numbers that appear random at first, but have patterns over time. This makes it at least partially predictable and thus vulnerable to decoding.
To make encryption more secure, researchers have turned to quantum mechanics. There, the laws of physics ensure that the results of certain measurements – for example when a radioactive atom decays – are truly random.
The light should fluctuate
A popular way to make quantum randomness your own: Take advantage of the fluctuations in the light particles emitted by the laser material. Modular lasers are designed to reduce fluctuations to produce light of a constant intensity. They cause light waves to bounce back and forth in matter to force the atoms to emit more and more photons simultaneously.
But when it comes to generating random numbers, researchers aim the opposite. “We want the density to fluctuate randomly so we can digitize the density to generate random numbers,” says Hui Cao, study co-author and applied physicist at Yale University in New Haven, Connecticut.
Cao and her team created their own laser in the shape of a fly. It is a semi-conductive semiconductor. The photons bounce several times between the curved walls of the fly before emerging again as a scattered beam. The scientist and her colleagues can then capture the light with an ultrafast camera. They recorded the light output from 254 independent pixels, which together produced random bits at a rate of about 250 terabits per second, or 250 terrahertz. These are several orders of magnitude faster than previous devices of this type, which only took one pixel at a time.