Is Google’s new Willow quantum computer really such a big deal?

Google has unveiled a new quantum computer and once again claims to be ahead in the race to show that these exotic machines can outperform even the world’s best conventional supercomputers; so does this mean useful quantum computers are finally here?

Researchers at the tech giant were the first in the world to demonstrate this feat, known as quantum supremacy. advertisement Sycamore quantum computing chip in 2019. But since then, supercomputers have caught up, leaving Sycamore behind. Now, Google has created a new quantum chip, called Willow Julian Kelly Google says in Quantum AI that it is the best in the company.

“You might think it has all the benefits of Sycamore, but if you looked under the hood, we changed the geometry … we reimagined the processor,” he says.

While the most advanced version of Sycamore had 67 qubits, or quantum bits, for processing information, has been upgraded to the Willow 105. Ideally, larger quantum computers should also be more powerful, but researchers have found that qubits in larger devices can remain coherent, losing quantumness. The competitors have also seen that IBM and California startup Atom Computingboth recently debuted quantum computers with more than 1000 qubits.

Because of this, Kelly says, the quality of the qubits has been a big focus for the team, and Willow’s qubits can store their entangled quantum states – and thus reliably encode information – for up to five times longer than Sycamore’s.

Google uses a specific benchmarking task called RCS to evaluate the performance of its quantum computers, which Willow pointed out. Hartmut NevenAlso in Google Quantum AI. The task is to verify that a sample of numbers produced by a program running on the chip has the most random distribution possible. For several years, Sycamore could do this faster than the world’s best supercomputers, though in 2022and then again in 2024new records were set by conventional computers.

Google says Willow has once again widened the gap between quantum and traditional machines, with the task taking 5 minutes on the chip, and the company estimates it would take 10 septillion years, or much more than the squared age of the universe, at its peak. supercomputer

In this comparison, the researchers modeled a version of the Frontier supercomputer (which was recently it has fallen to only the second most powerful supercomputer in the world) with more memory than it’s currently capable of using, only underlines Willow’s computing power, Neven says. While Sycamore’s records were broken, Willow is sure to maintain its champion status for many more as conventional computing methods reach their limits.

What is still unclear is whether Willow can actually do anything useful, as the RCS benchmarking test has no practical application. Kelly says success in the benchmark is a “necessary but not sufficient” condition for the utility of a quantum computer, although any chip that doesn’t excel at RCS has no chance of being practical later on.

But the Google team has another reason to believe in Willow’s bright future: it’s very good at correcting its mistakes. It is the tendency of quantum computers to make mistakes one of the biggest problems today, it prevents them from fulfilling their promise of being more powerful than any other type of computer. To improve this, researchers, including Google’s team, join physical qubits together to form “logical qubits”, which are much more resilient to errors.

With Willow, the team showed that as logical qubits got bigger, they got better at preventing errors, making about half as many errors as the physical qubits that made them up. Furthermore, this error rate was further halved when the logic qubits roughly doubled in size. In this way, Google researchers reached a threshold where they believe they can continue to increase the number of qubits – making ever larger quantum computers – and improve the execution of calculations, which has not been the trend so far.

“This is, in my opinion, a signature result, and while we are far from demonstrating a practical quantum computer, it is an important and necessary step towards that goal,” he says. Andrew Cleland at the University of Chicago.

Martin Weiss The new work, from the University of Glasgow in the UK, says it paves the way for building “fault-tolerant” quantum computers that can catch and correct all errors. Challenges remain, but these advances pave the way for transformative applications in quantum chemistry, such as drug discovery and materials design, as well as in cryptography and machine learning.

The focus on error correction Advances in logical qubits in academic labs and the growing quantum computing industry have made it an important point of comparison between today’s best quantum computers. In 2023, a team of researchers from Harvard University and the startup QuEra used qubits made from very cold rubidium atoms. set a record for the most logical qubits ever created. At the beginning of the yearResearchers at Microsoft and Atom Computing linked a record number of logical qubits using quantum entanglement.

Google’s approach is different because it focuses on making single logical qubits bigger and better, rather than maximizing their number. “We could divide our chip into smaller and smaller logical qubits and run algorithms, but we really wanted to get to that threshold. That’s where all the underlying science and engineering challenges (of quantum computing) lie,” says Kelly.

Ultimately, however, the biggest test of Willow’s impact will be whether it can accomplish the same goal that all other quantum computers seek: to reliably calculate something useful but not possible on any conventional computer. Neven says Sycamore has already been used to make scientific discoveries, such as in quantum physics, but the team is putting Willow into more real-world applications. “We are moving towards new calculations and simulations that classical computers could not do.”