We’ve finally cracked how to make truly random numbers

Ini, mini, mini, mo, catch the tiger by the finger – this is how the rhyme sounds. But even children know that such counting rhymes will not help make a truly random choice. Perhaps you remember the first time you realized you could change your outcome by choosing your starting point carefully?

Flipping a coin or rolling a dice might be better, but try to prove that the result of your toss or roll is random and you will reach a dead end. This is because these things are not truly random: if you knew the exact position of the die or coin in your hand, the trajectory of the throw, the strength of gravity, and subtle factors such as air resistance or the friction of the landing surface, you could predict the outcome. True chance hard to find.

The point is that we now know that randomness is real, built into the very fabric of the Universe in the form of quantum mechanics. Given a choice of two paths, a quantum entity – such as an electron or a photon of light – will choose one completely at random: there is no predictable cause behind a quantum effect. The University of Colorado's Beacon of Randomness, affectionately nicknamed CURByexploits this phenomenon. It went online this year as the world's first publicly available source of trackable, verifiable and truly random numbers.

You might wonder who needs such radical randomness. After all, people have enjoyed rolling dice and tossing coins for thousands of years. But there are applications in which it is important to generate as much randomness as possible. “People don’t realize it, but without randomness, digital life wouldn’t be safe or fair,” says Nemitari Aienkacomputer scientist interested in testable randomness at Nottingham Trent University in the UK. Every time you connect to a secure web page or generate a secure password, there is a certain level of randomness involved, he said. And machine learning has randomness built into it.

Another use is to support democracy. In Chile, for example, politicians and civil servants are subject to random tax audits, and those chosen tend to argue that the system is targeting them for nefarious reasons. “Everyone is complaining it’s a witch hunt,” says Christer Schalmco-creator of CURBy at the US National Institute of Standards and Technology (NIST). These statements are much more difficult to make if the system uses a random beacon whose numbers are derived from truly random sources.

At the moment, the Chilean government receives its randomness from the analysis, among other things, seismic activity and production of the radio station of the University of Chile. But this is still not entirely accidental: after all, seismic activity does not just happen, and someone determines the playlist of a radio station. Nor is it fully traceable, given that people cannot regularly access seismic data. However, CURBy is both.

Quantum randomness generator

Ten years ago, Shalma said, the system was “held together with duct tape and prayers.” That's when the researchers behind it first conducted a painstaking proof of the CURBy principle. During this time, they worked to make the system fast, automated and ready to be used – at any time – by anyone with Internet access.

CURBy is now a state-of-the-art tool that processes thousands of user requests every day. This could help strengthen democracy, increase trust in judicial systems, and even bring harmony to family game night. “CURBy represents a working, publicly available quantum technology. This is an exciting development for me,” says Peter Brownphysicist at the Paris Polytechnic Institute.

“
People don't realize it, but without randomness, digital life wouldn't be safe.
“

Generating truly random numbers is difficult. Very little in the universe operates according to the principle of true randomness, because unless you are dealing with quantum materialThere is always a mechanism for generating numbers. Even computers that spit out “pseudo-random” numbers to create strong passwords can be fooled. Passwords are generated from a “seed” number, and if you know the seed and the algorithm, there is nothing random about them at all.

You could go further and use “high-entropy” sources of randomness, such as the unpredictable timing of the radioactive decay of a piece of material – for example, cobalt-60 or strontium-90. This is a random quantum event, but it difficult to make user-friendly. And if there's no one in the room with you, you won't always be able to prove that you didn't just make up the numbers.

This also makes playing Yahtzee quite dangerous – and now that CURBy is available, there's simply no need to expose family members to radiation. Instead, CURBy relies on pairs of photons linked by a quantum phenomenon called quantum entanglement.

When two entities are entangled, they behave as if they are in some way one. This strange situation occurs when you take a measurement on one of the objects and then take a similar measurement on the other. Under certain circumstances, the first measurement influences the result of the second, even if quantum objects were moved to opposite sides of the Universe and could not exchange any information. It's like rolling two dice and finding that if one rolls a 6, the other always rolls a 1.

Entanglement between quantum objects, known as Albert Einstein's “spooky action at a distance,” defies common sense: it occurs without any signal being transmitted between them. No one has ever figured out a physical mechanism for how this happens.

Inside CURBy, entanglement manifests itself in measurements of a property called polarization. Pairs of entangled photons are separated and sent along optical fibers to two destinations 100 meters apart. At each location, the instrument measures the polarization, with a very short time between two measurements.

Further, measurement results are “correlated”: there is a subtle relationship between the results, the extent of which CURBy can analyze. Under “classical” conditions there is an upper limit to this power, but if the behavior is truly quantum and therefore random, the limit is exceeded and can be used to produce random numbers. This is done by “purifying” the inherent randomness using a method called Trevisan extraction. CURBy can perform about 250,000 polarization measurements per second, and it takes about 15 million measurements to produce the final product: a string of 512 truly random binary digits, or bits, that people can use as they see fit.

If you want to know exactly how random these bits are, there's an algorithm for that. Considering there are 512 bits in a string and each bit can be 0 or 1, that means there are 2 of them.⁵¹² possible combinations. “It’s a huge amount of opportunity,” Shalm says.

They should all appear with equal probability, and Shalm and his colleagues were able to measure the probability of a particular string of bits appearing. It is not perfectly smooth, but it may well be so. Think of it as wanting to have a completely smooth road. If the slope is 1 in 10, it is a steep hill. Even 1 out of 100 – 1 meter of rise per 100 meters of road – is noticeable. The gradient equivalent to CURBy randomness is 1 in over 184 quintillion: as random as anyone needs.

Proof of randomness

“Randomness isn’t the only advantage of CURBy—in fact, the main thing is that anyone can trace the origin of the numbers and prove that they are random,” says Shalm. “Currently there is no good way to do this using any kind of random number generator,” he says.

To trace their randomness, CURBy researchers borrowed data from blockchain mathematics used to guarantee the security of digital assets such as NFTs and cryptocurrencies. Essentially, it is a way to verify what was done, when, and by whom (in a scenario where no one trusts anyone), and everything can be traced back to the original result of the experiment.

Another factor that makes it difficult for anyone to cheat the system is that the entire process is distributed among various institutions. NIST submits the quantum data to processing facilities at the University of Colorado Boulder, and then an independent cryptography service known as the Distributed Randomness Beacon Daemon adds its own set of ingredients to extract the true randomness contained in the measurement data and convert it into a final, uniform binary string.

“It’s almost like a web of connected, time-ordered things,” Shalm says. “No party has complete control over what the random bits are, and you can go back and see if anyone cheated or tried to change something.”

The integration of all the necessary physics with high-level safety analysis is “quite remarkable,” Brown says. Quantum technologies They are typically still in the development stage, he notes, and there are few finished products available. But will CURBy be useful? Absolutely, says Brown – although there are applications where you definitely shouldn't use tracked randomness. “You don't want to choose your passwords based on a publicly available source of randomness,” he says.

But selecting juries and judges in cases, obtaining lottery results, and randomizing samples in clinical trials are just a few examples where traceable randomness would be a benefit. Oxford University mathematician Arthur Eckert Impressed too. The way the CURBy team combined quantum and classical physics to create cutting-edge yet affordable technology is a sign of the future, he says.

In fact, Shalm says, CURBy itself is specifically designed to be compatible with other technologies that will emerge in the future. In other words, true randomness will be built into our entire future, making the world a fairer and safer place. It's definitely better than flipping a coin.

Topics: