The issue of quantum supremacy - the point at which quantum computers are able to demonstrate a tangible advantage over classical systems - is dicey to say the least.

When Google claimed it had achieved quantum supremacy in 2019, it was almost immediately called out by IBM. Big Blue questioned several of the assertions Google made in the paper, and estimated a classical system could produce results with higher fidelity than Google achieved with a 53 superconducting qubit quantum computer, and could do it in just 2.5 days - not the 10,000 years researchers had claimed.

This week, Quantinuum revisited the issue, boasting that it had achieved a greater than 100x improvement over Google's 2019 results.

If you're not familiar, the startup was formed as part of a merger between Britain's Cambridge Quantum and Honeywell Quantum Solutions in the US.

Rather than the superconducting quantum systems deployed by Google, IBM, and others, Quantinuum uses trapped-ion qubits, which use electromagnetic fields to suspend charged particles in free space.

Quantinuum's latest benchmark, conducted in collaboration with JPMorgan Chase and researchers from Caltech and Argonne National Laboratory, tried a different system, called the H2-1, which features 56 trapped ion qubits.

The demonstration, detailed in this paper, involved an algorithm called random circuit sampling and measured the quality of the results using a variety of tests including something called the linear cross entropy benchmark (XEB).

A XEB score closer to zero represents a noisier and therefore less efficient system. Scores closer to one indicate more effective quantum computing.

As Quantinuum explains it, Google was able to achieve a score of roughly 0.002. That's awfully close to zero, and the Chocolate Factory argued it was a statistically significant improvement over classical systems of the time. By contrast, Quantinuum says its 56 qubit H2-1 system managed to achieve an XEB score of roughly 0.35.

This was apparently possible by using fresh wiring and network topologies which had made it difficult for the qubits to communicate in an all-to-all manner, at scale.

If Quantinuum is to be believed, its new H2-1 system is so potent that it's now impossible to emulate the machine on conventional hardware, "as it would take up the entire memory of the world's best supercomputers." Because of that, it's discontinuing its quantum emulation platform, which allowed you to simulate one of their machines on conventional hardware.

They estimate their system can process some jobs using 30,000 times less energy than would be required by a conventional system. But to be clear, the biz isn't claiming quantum supremacy and, while a substantial improvement over Google's 2019 results, it admits there's a lot of work left to do.

"The H2 quantum computer produces results without making even a single error about 35 percent of the time," Quantinuum wrote in a canned statement on Wednesday.

That might not sound that reliable - and it's not - but it argues that "35 percent is still a significant step towards the idealized 100 percent fidelity limit in which the computational advantage of quantum computers is clearly in sight.

"These results show that whilst the full benefits of fault tolerant quantum computers have not changed in nature, they may be reachable earlier than was originally expected, and crucially, that along the way, there will be tangible benefits to our customers in their day-to-day operations as quantum computers start to perform in ways that are not classically simulatable," Ilyas Khan, Quantinuum chief product officer, explained in a statement.

Quantinuum's tech has garnered considerable attention over the past few months. Back in January, quantum computing's potential to accelerate complex financial workload convinced JPMorgan to inject $300 million into the biz.

That same month, Japan's government scientific research institute Riken revealed it would deploy the startup's trapped-ion systems at its research facility in Wako, Saitama.

Then, in April, Quantinuum teamed up with Microsoft on a qubit virtualization system, which was used to generate what it claimed were the "most reliable logical qubits ever recorded," by using 30 physical qubits to create four logical ones.

Quantinuum is just one of many quantum computing startups. Established tech players like IBM and Fujitsu are also in the game.

And the game is afoot: One of the most ambitious projects in this arena includes a $100 million system spearheaded by IBM, and the universities of Chicago and Tokyo are expecting to build a 100,000 qubit quantum system by 2033. ®

https://www.theregister.com//2024/06/07/quantinuum_new_computer/