Understanding randomness is crucial in many fields. From computer science and engineering to cryptography and weather forecasting, studying and interpreting randomness helps us simulate real-world phenomena, design algorithms and predict outcomes in uncertain situations.
Randomness is also important in quantum computing, but generating it typically involves a large number of operations. However, Thomas Schuster and colleagues at the California Institute of Technology have demonstrated that quantum computers can produce randomness much more easily than previously thought.
And that’s good news because the research could pave the way for faster and more efficient quantum computers.
Shuffling in the quantum world
Unlike classical computers that encode information in “bits” (either zeros or ones), the basic unit of information in quantum computing is the quantum bit or qubit. Arranging or shuffling these qubits in random configurations is one way scientists have demonstrated how quantum computers can outperform classical ones. It’s known as the quantum advantage.
Shuffling qubits is a bit like shuffling a pack of playing cards. The more you add, the harder it becomes and the longer the process takes.
Also, the more you shuffle in the quantum world, the greater the chance of ruining the delicate quantum state of each qubit. For this reason, it was thought that only small quantum computers could handle applications that relied on randomness.
What the team at the California Institute of Technology has done is show that these random qubit configurations can be produced with fewer shuffles. So, how did they do it?
They imagined splitting a group of qubits into smaller blocks and then proved mathematically that each block could generate randomness.
Describing their research in a paper in Science, the team showed how these smaller qubit blocks could be “glued” together to create a well-shuffled version of the original qubit sequence.
As a result, it may be possible to use randomly arranged qubit sequences on larger quantum systems. That means it could be easier to build more powerful quantum computers for tasks such as cryptography, simulations and a host of other real-world applications.
Deeper implications
The researchers also believe their findings point to something even deeper. Namely, there may be fundamental limits to what we can observe in nature because quantum systems hide information incredibly quickly.
“Our results show that several fundamental physical properties—evolution time, phases of matter, and causal structure— are probably hard to learn through conventional quantum experiments. This raises profound questions about the nature of physical observation itself.”
Written for you by our author Paul Arnold,
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More information:
Thomas Schuster et al, Random unitaries in extremely low depth, Science (2025). DOI: 10.1126/science.adv8590
Naoki Yamamoto et al, Shrinking quantum randomization, Science (2025). DOI: 10.1126/science.adz0147
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Improving randomness may be the key to more powerful quantum computers (2025, July 4)
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