NIST and Partners Harness Quantum Physics to Create Random Number Generator Factory
- ritambhara516
- 5 days ago
- 5 min read
Instrumentation for the quantum random number generator in the NIST Boulder laboratories. Credit: NIST
Randomness plays a surprisingly important role in everyday life. We use it to make fair decisions—like drawing straws, rolling dice, or flipping coins—and it's essential in fields like auditing, where it helps ensure unbiased selections. Random numbers are especially crucial in digital security: the more unpredictable a password or encryption key is, the harder it is to break.
But here’s the catch—how can we be sure that something is truly random? Most computer-generated random numbers aren’t truly random at all. They’re created by algorithms, which means that with enough knowledge about how the system works, someone could potentially predict the outcome. The same goes for physical randomness—an expert magician might rig a coin toss, and even a perfectly honest flip can be influenced by subtle factors that make the result more predictable than we realize.
“True randomness is something no part of the universe can foresee,” explains Krister Shalm, a physicist at the National Institute of Standards and Technology (NIST). He points out that even when we use natural processes to generate random numbers, it’s still hard to prove those numbers are genuinely unpredictable.
Einstein famously rejected the idea that the universe is random, once saying, “God does not play dice with the universe.” But over time, scientists have shown that he was mistaken—at least when it comes to quantum mechanics. Unlike dice rolls or computer-generated numbers, quantum processes are fundamentally unpredictable.
Building on this principle, physicist Krister Shalm and his team have harnessed true quantum randomness using a type of experiment known as a Bell test. Their work has turned this pure form of unpredictability into a reliable and verifiable random number service, with their findings recently published in Nature.
“If God does play dice with the universe,” Shalm joked, “we figured out how to turn that into the best random number generator nature can offer.” His team’s goal was to move beyond a lab experiment and create something useful for the public.
That effort led to the creation of the Colorado University Randomness Beacon, or CURBy. Developed by researchers at NIST and the University of Colorado Boulder, CURBy automatically generates quantum-based random numbers and shares them online daily—free for anyone to use.
At the core of this new service is a Bell test run by NIST, which generates genuinely random outcomes. Think of it as the raw ingredient—the purest form of unpredictability—that researchers then process and refine into the random numbers shared by the CURBy beacon.
The Bell test involves measuring pairs of entangled photons—particles of light that remain mysteriously linked no matter how far apart they are. When one is measured, the result is completely random, yet the two photons still show stronger connections than classical physics can explain. This strange behavior, which Einstein famously referred to as "spooky action at a distance," allows scientists to not only generate randomness but also prove that it's genuinely unpredictable.
CURBy is the first public random number generator to rely on this phenomenon of quantum nonlocality as its source. It’s also the most transparent and verifiable system of its kind. Unlike conventional generators, CURBy’s random bits can be certified with high confidence, thanks to their quantum origin.
“CURBy is one of the first publicly available services that operates with a proven quantum advantage. That’s a big step forward,” said Krister Shalm. “We can directly verify the quality and source of the random numbers—something traditional methods just can’t do.”
NIST has been a pioneer in this area. Back in 2015, it carried out one of the first full-scale Bell tests to confirm that quantum mechanics really does produce true randomness. By 2018, NIST had already begun turning those insights into practical tools, laying the foundation for the world’s first certified sources of randomness.
Turning quantum entanglement into usable random numbers isn’t easy. In fact, when NIST first demonstrated the Bell test, the setup took months to prepare and could only run for a few hours. Even then, it generated just 512 bits of true randomness—a tiny amount by today’s standards.
Since then, Krister Shalm and his team have worked hard to improve the system, making it more reliable and automated so it can deliver random numbers on demand without constant manual oversight. Their efforts paid off: in the first 40 days of continuous operation, the system successfully produced random numbers in 7,434 out of 7,454 runs—a success rate of 99.7%.
The process begins with the creation of a pair of entangled photons inside a specially designed nonlinear crystal. These photons are then sent through optical fibers to separate labs located at opposite ends of a hallway. Once they arrive, their polarization—the direction in which they oscillate—is measured. These measurements produce truly random outcomes, and the system repeats this process an astonishing 250,000 times per second.
The millions of random results generated by these quantum "coin flips" are then sent to a computer program at the University of Colorado Boulder. There, they go through a series of careful processing steps and strict protocols that transform the data into 512 random bits—strings of 0s and 1s. These bits are completely unpredictable, representing pure randomness that even Einstein couldn’t have foreseen. In essence, it’s like performing the universe’s most honest coin toss.
To ensure complete transparency and trust in the process, NIST and its partners developed a new verification system. They created the Twine protocol, an innovative quantum-friendly blockchain framework. Twine allows multiple organizations to jointly generate, track, and certify the random data from the Bell test. Each batch of random numbers published by the CURBy beacon is marked with a digital “hash”—a kind of fingerprint used in blockchain technology—making every step in the process traceable and verifiable.
The Twine protocol makes it possible for anyone to verify the source of each random number, says Jasper Palfree, a research assistant at the University of Colorado Boulder working on the project. What’s more, the protocol is designed to scale—allowing other random number generators to join the system and contribute to a shared network of randomness. No single group has control, and everyone can take part.
By linking these random number sources together through hash chains—essentially digital fingerprints—the protocol timestamps each set of data, creating a secure and traceable structure. This setup not only helps keep everything transparent but also makes it easy to detect any tampering.
“The Twine protocol lets us weave multiple beacons together into a kind of trust network,” Palfree explained.
That idea—turning an advanced quantum physics experiment into a practical, public service—is exactly what drew graduate student Gautam Kavuri to the project. The entire process is open-source and freely available, so anyone can check the results, contribute, or even use the system to build their own random number generator.
CURBy’s random numbers can be applied to any situation where a neutral, public source of randomness is needed—like selecting jury members, conducting fair audits, or distributing resources through public lotteries.
“I wanted to build something that’s not just cutting-edge science, but actually useful,” said Kavuri. “At NIST, you’re encouraged to pursue bold, meaningful projects that serve the public—and this was one of those.”