“That’s so random” is a common saying people use when they see or experience something unexpected. But as a concept in physics, true mathematical randomness has long proven elusive — until now. A team of computer scientists using quantum computing methods has, for the first time, generated a truly random number, they report in the journal Nature.
By now you’re asking yourself, what is “true randomness,” anyway? Doesn’t choosing a number between, say, one and a trillion, count as truly random?
Physicists would say “no.” Every existing seemingly random task still operates under physical or mathematical rules.
Certified Randomness Theory
The ability to create randomness that can truly be proven as such is called certified randomness, and is more than an esoteric, mind-boggling mathematical exercise. It can, in theory, make encryption much more secure, or ensure that processes such as jury selection are truly fair.
Such certification it turns out, is as tricky as generating the random number. It requires proving that the computer checking for randomness is truly an independently operating third party.
“The main challenge for any client receiving randomness from a third-party provider, such as a hardware security module, is to verify that the bits received are truly random and freshly generated,” according to the paper.
To create their random number, the researcher used a technique called random circuit sampling. It essentially leans on quantum computing (which operates under different rules than classical computing methods) that somehow produces more randomness than it can take in. This task is unachievable by classical computation.
Read More: New Microsoft Quantum Computing Chip Could Revolutionize the Industry
Putting Quantum Computing to the Test
The research had two steps. First, the team generated random circuits and sent them to an untrusted remote quantum computer via the Internet, according to a press release. That computer was then asked to return corresponding samples. This back and forth was so fast it could not be replicated by even the fasted conventional (i.e., non-quantum) supercomputer.
Just how fast was it? The output performed more than one million trillion operations per second — which is really, really fast.
To certify that the number generated was indeed truly random, the researchers essentially asked a non-quantum supercomputer to guess what it was. The supercomputer, it turns out, was not up to the task. Therefore, the output could indeed be certified as truly random.
“This work marks a major milestone in quantum computing, demonstrating a solution to a real-world challenge using a quantum computer beyond the capabilities of classical supercomputers today,” Marco Pistoia, a computer scientist with JPMorganChase and an author of the study, said in a press release. “This development of Certified Randomness not only shows advancements in quantum hardware, but will be vital to further research, statistical sampling, numerical simulations and cryptography.”
In other words, the number the team generated through its quantum computer really was random.
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Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.
