The advancement of Google's Willow quantum chip is hidden behind a questionable evaluation standard.
On Wednesday, Google introduced Willow, its new quantum chip, and if you have been browsing the internet since then, you have probably come across numerous enthusiastic reactions to it.
Google unveiled its new quantum chip called Willow on Wednesday, generating a wave of enthusiastic media coverage. Various headlines highlight how Willow could "outpace classical computers on a cosmic timescale" and describe this quantum chip as "incredible." The basis for such claims is that Willow can perform calculations that, theoretically, would take a classical computer much longer than the time the universe has existed, which is 14 billion years. However, the significance of this advancement is more complex than it seems.
Unlike its previous quantum chip Sycamore, which was unveiled in 2019 and which Google claimed achieved quantum supremacy, Willow does not seek to make such a claim. At that time, Google emphasized that Sycamore performed an operation in just 200 seconds, which would have taken the world’s fastest supercomputer approximately 10,000 years. This achievement led to the assertion that its quantum computer could solve problems that the best classical computers could not tackle. However, this claim sparked controversy, with critics arguing that it was not valid. Since then, Google has stopped referring to quantum supremacy and has limited itself to stating that it has achieved "calculations beyond the classical."
The dilemma lies in the fact that Sycamore was designed to excel at a single specific task known as random circuit sampling (RCS), which, according to Google itself, "has no known practical applications." Despite this, they are now again promoting performance in RCS. Currently, Google claims that Willow can complete its latest RCS test in under five minutes, while it is estimated that Frontier, the second most powerful supercomputer in the world, would take 10 septillion years to perform the same task. This figure, according to Google, reinforces the idea that quantum computing occurs across multiple parallel universes, aligning with the multiverse theory.
On the other hand, Google argues that performance in RCS should be the standard measure for evaluating all quantum computers. Hartmut Neven, founder of Google Quantum AI, states that "it is a starting point. If you can't win at random circuit sampling, you can't win at any other algorithm." However, companies like IBM and Honeywell use a metric called quantum volume to highlight their advances, which offers a more comprehensive understanding of a machine’s capabilities by considering how its qubits interact. Nonetheless, quantum volume is not mentioned in the specifications for Willow, making comparisons more difficult.
The most noteworthy claim Google makes about Willow is that it is "below the threshold." This threshold refers to the challenge faced by all attempts thus far to create practical quantum computers, due to the difficulty in controlling qubits, which will only maintain their quantum state for fractions of a second, and the tendency to make errors when adding more qubits. However, Google claims to have found a way to reduce these errors by incorporating more qubits into the system. According to the company, Willow is the first time this has been achieved.
Neven notes that "as the first system below the threshold, this is the most convincing prototype for a scalable logical qubit built to date. It is a strong indication that useful, large-scale quantum computers can be built." This suggests a future possibility where quantum computers could solve problems with tangible effects on people's lives. However, that reality has not yet arrived, and Google acknowledges that there is more work to be done before reaching that goal.
