New quantum computer sets world record

Scientists at the American quantum computing company Quantinuum have conducted several tests to evaluate the performance of the H2-1, a new quantum computer that integrates 56 qubits, and the quality of the qubits used.Live Sciencereported on July 11. The research results were published on the databasearXiv.

Quantum computers can perform multiple calculations in parallel thanks to the laws of quantum mechanics and the entanglement of qubits, while traditional computers can only operate sequentially. Adding qubits to the system increases the computer's power exponentially. Scientists predict that in the future, quantum computers will be able to perform complex calculations in seconds that would take traditional supercomputers thousands of years.

The point at which a quantum computer surpasses a traditional computer is called quantum supremacy, but to reach this milestone in a practical way, a quantum computer needs millions of qubits. The largest machines available today have only about 1,000 qubits. The reason such a huge number of qubits are needed for quantum supremacy is that they are inherently error-prone, so a lot of them are needed to correct those errors. Many researchers are now focused on making qubits more reliable, rather than just adding more qubits.

In the new study, the team tested the accuracy of H2-1's output data using the Linear Cross Entropy Evaluation (XEB) protocol. XEB produces results ranging from 0 (all output errors) to 1 (no errors at all).

Google first tested the Sycamore quantum computer using XEB in 2019, demonstrating that it could complete a calculation in 200 seconds that would have taken the most powerful supercomputer at the time 10,000 years. They recorded an XEB result of about 0.002 with 53 superconducting qubits integrated into Sycamore.

In the new study, scientists at Quantinuum and JPMorgan, the California Institute of Technology (Caltech), and Argonne National Laboratory recorded an XEB score of about 0.35. This means that the 56-qubit H2-1 quantum computer produced results without errors 35 percent of the time.

“35% is a significant step towards the ideal 100% accuracy limit,” Quantinuum said. In addition, the new quantum computer also runs algorithms with 30,000 times less energy than traditional computers.