It’s something from nothing. A random number generator that harnesses the quantum fluctuations in empty space could soon sit inside your computer.

A device that creates truly random numbers is vital for a number of applications, including cryptography.

Algorithms can generate numbers that pass statistical tests for randomness, but they’re useless for secure cryptography if the algorithm falls into the wrong hands. Other methods using entangled ions to generate random numbers are more reliable, but tend to be slower and more expensive.

Now Christian Gabriel’s team at the Max Planck Institute for the Science of Light in Erlangen, Germany, has built a prototype that draws on a vacuum’s random quantum fluctuations. These impart random noise to laser beams in the device, which converts it into numbers.


“It’s an easy method, and it’s good value,” says Gabriel.

The team sent a laser into a beam splitter, sheltered from external light sources. Without influence from the vacuum, the two emerging beams would have been identical. However, the lowest energy state of the electromagnetic field carries just enough energy to interact with the laser as it passes through the beam splitter. “The beams carry this quantum noise,” says Gabriel.

The exiting beams were captured in two detectors which turned the light into electronic signals, and the signals were subtracted from one another, leaving only the noise from the vacuum and electronics. The team used a mathematical function to tease out the truly random signal of the vacuum. Because they could calculate the total disorder in the system and the portion which comes from the vacuum, they were able to reduce the set of numbers so that the electronic contribution was eliminated and only a fully random string remained.

Though reduced, the stream of bits comes at speedy 6.5 million per second. This is already in line with the speed of commercially available quantum random number generators, say the researchers, but they hope to achieve rates more than 30 times higher.

Collaborator Christoph Marquardt says the generator’s optimised speed will be “faster than anything you could buy or that is available in other comparable systems nowadays”.

The lab set-up costs about €1000, and the researchers estimate that the cost could fall to about €100. As the device functions at room temperature and could be made to fit in the palm of your hand, it may one day be integrated into a desktop computer.

Antonio Acín of the Institute for Photonic Sciences in Barcelona, Spain, points out that although the quantum noise of the vacuum is tamper-proof, most users won’t be able to verify the workings of their random number generators – meaning they’ll find it impossible to tell whether they are receiving a unique random stream from the generator or a pre-programmed, statistically random set from elsewhere.

Journal source: Nature Photonics, DOI: 10.1038/nphoton.2010.197