How do you generate truly random numbers?

When you toss a dice you might think the outcome is random, but it’s not. It is merely complex.

In a classically complex system like a dice roll, tiny changes in the starting conditions, such as how you’re holding the dice, lead to very different outcomes, but it’s not really random.

If it were possible to throw the dice again keeping everything, including minor details like air currents, exactly the same, it would inevitably come up with the same number.

If you want to create the perfect casino, or more importantly, deliver good random data for things like climate models, what do you do?

You visit the ANU Quantum Random Numbers Server.

Professor Ping Koy Lam and Dr Syed Assad lead a group of scientists at the ANU Research School of Physics and Engineering who have created one of the world’s first sources of large quantities of truly random data.

The ANU Quantum Random Number Server is available online, 24 hours a day and 365 days a year. The website can be accessed from anywhere around the world. Anyone who downloads random numbers from the ANU website will be sure to get a fresh and unique sequence of numbers that is different to all other users.

The server has received a staggering 200 million hits from over 80 countries. It services the scientific community looking for random data streams to feed encryption systems, global climate modelling, stock market forecasting, air traffic control simulation, and electronic gaming.

“Our numbers are truly random and unbiased because we extract them directly from quantum fluctuations in vacuum,” Professor Lam explains. “It’s physically impossible for them to form a predictable sequence.”

For some applications it doesn’t matter if a data stream is predictable so long as the numbers statistically average out to random, but for others it is out of the question.

“We’re heavily involved in quantum encryption systems that ensure secure communications,” Professor Lam says.

“One of the cornerstones of such systems is that the encryption key is truly random. If you get those keys from the type of pseudo-random number generators found in most computers then you introduce a potential weakness into an otherwise impregnable system.”

Another issue that arises with pseudo-random generators is that eventually the numbers repeat. It’s not a problem if you just take a few thousand or even million, but sophisticated computer models often require trillions and trillions of numbers. Hidden repeating sequences can easily corrupt such models leading to incorrect conclusions and wasting vast amounts of human and computer time. However with data from the quantum vacuum, there is no possibility of any such problems arising.

How exactly do you extract quantum noise from a vacuum? The key lies in the fact that there’s really no such thing as a true vacuum.

The vacuum was once thought to be completely empty, dark, and silent until the discovery of modern quantum theory. Since then scientists have known that even ‘empty’ space has virtual sub-atomic particles spontaneously appearing and disappearing countless times per second.

This “vacuum noise” is widespread and ultimately poses a limit on the performance of fibre optic communication, radio broadcast, and computer operation. While this has always been seen as an annoyance that engineers and scientists need to circumvent, Professor Lam’s team instead measure these fluctuations to generate their random numbers.

The researchers are currently able to generate billions of random numbers every second, with the speed of the online random number generator limited only by bandwidth and the capacity of internet connections.

That’s a lot of rolls of the dice.