Figure 1: A close-up of the trapped-ion quantum computer used to simulate quantum-information scrambling circuits. © 2025 Quantinuum
Four RIKEN researchers have used two small quantum computers to simulate quantum information scrambling, an important quantum-information process1. This achievement illustrates a potential application of future quantum computers.
Still in their infancy, quantum computers are only just beginning to be used for applications. But they promise to revolutionize computing when they become a mature technology.
One possible application for quantum computers is simulating the scrambling of quantum information-a key phenomenon that involves the spread of information in quantum systems ranging from strange metals to black holes.
After encoding information in one part of a quantum system, it becomes diluted over time through various processes. Eventually, it spreads out across the whole system.
The original information is not lost, but it is much harder to reconstruct since you need access to the entire system. The quantum-information scrambler par excellence is the black hole, which is the ultimate shredder when it comes to quantum information.
Understanding how information scrambling occurs is critical for addressing fundamental problems in quantum physics.
"Quantum-information scrambling is of interest to us because we can use it to do some additional calculations, such as statistical physics calculations," says Kazuhiro Seki of the RIKEN Center for Quantum Computing (RQC).
One way to study quantum-information scrambling is to perform simulations, which is where quantum computers can help since they are better suited for such simulations than conventional computers.
Now, Seki and Seiji Yunoki, also of RQC, and two co-workers, have used two quantum computers with 20 qubits-the quantum equivalent of bits-to simulate quantum-information scrambling circuits (Fig. 1).
For the simulation, the researchers used state-of-the-art quantum computers via the cloud, which are based on qubits formed from trapped ions. They used the quantum computers to perform three simulations, which included creating a scrambled state and using it to perform quantum statistical mechanical calculations.
While a powerful conventional computer could have been used to perform the simulation, the complexity of simulations is approaching the realm where quantum computers will be indispensable for such calculations.
"We only used 20 qubits to conduct the simulations in this study," says Yunoki. "If we can use more than 50 qubits to perform similar calculations, it may be too difficult for a classical computer to handle."
A 20-qubit, trapped-ion quantum computer was installed at RIKEN in February 2025. "We're hoping to upgrade it in the next couple of years, so that it will have around 50 qubits," Yunoki notes.
Figure 2: A photograph of the 20-qubit, trapped-ion quantum computer used to simulate quantum-information scrambling circuits. © 2025 Quantinuum
