In March 2018, Google unveiled a 72-qubit quantum computer chip named Bristlecone. With that hardware, the company was optimistic that it would achieve "quantum supremacy". Today, according to a report from the Financial Times, the researchers working with Google reportedly achieved the feat with Sycamore - a toned down, 53-qubit "version" of Bristlecone. The team announced its findings in a paper that was published on a NASA website. However, shortly after going online, the paper was taken down.
In the paper, the team of researchers claimed that their processor was able to perform a calculation, which would have taken the most advanced "classical" computers today over 10,000 years to work out. The 53-qubit quantum computer was able to solve it in just three minutes and 20 seconds, thereby achieving "quantum supremacy".
This is significant because this is the first time in history that we have demonstrated a problem that can only be solved by quantum computers, hence the phrase—"quantum supremacy". After all, a runtime of 10,000 years for a piece of computation is not feasible at all. The authors wrote in their paper:
This dramatic speed-up relative to all known classical algorithms provides an experimental realisation of quantum supremacy on a computational task and heralds the advent of a much-anticipated computing paradigm. To our knowledge, this experiment marks the first computation that can only be performed on a quantum processor.
While Steve Brierley, the founder of Riverlane, which is a start-up that develops software and algorithms for quantum computers, deemed it an "amazing achievement":
"It’s a significant milestone, and the first time that somebody has shown that quantum computers could outperform classical computers at all. It’s an amazing achievement."
The team also signaled the attainment of quantum supremacy to be "a milestone towards full-scale quantum computing". It also hypothesized the achievement to be a bane for Moore"s law, saying that the power of quantum computers will increase exponentially, not linearly.
Despite the impressive feat, quantum computers are still a fair way away from replacing traditional computers. Of course, it is an entirely different debate whether they will ever truly replace desktop PCs and laptops. But one thing is certain, the world of quantum computing is only meant to get more interesting.
Update: The quantum computer used for the problem was Sycamore (53-qubit design), not Bristlecone (72-qubit design). Changes have been made to the first and second paragraph that reflect this information.