Today, Google announced the results of their quantum supremacy experiment in a blog post and Nature article. First, a quick note on what quantum supremacy is: the idea that a quantum computer can quickly solve problems that classical computers either cannot solve or would take decades or centuries to solve. Google claims they have achieved this supremacy using a 54-qubit quantum computer:
Our machine performed the target computation in 200 seconds, and from measurements in our experiment we determined that it would take the world’s fastest supercomputer 10,000 years to produce a similar output.
You may find it helpful to watch Google’s 5-minute explanation of quantum computing and quantum supremacy (see also Nature’s explainer video):
IBM has pushed back on Google’s claim, arguing that their classical supercomputer can solve the same problem in far less than 10,000 years.
We argue that an ideal simulation of the same task can be performed on a classical system in 2.5 days and with far greater fidelity. This is in fact a conservative, worst-case estimate, and we expect that with additional refinements the classical cost of the simulation can be further reduced.
Because the original meaning of the term “quantum supremacy,” as proposed by John Preskill in 2012, was to describe the point where quantum computers can do things that classical computers can’t, this threshold has not been met.
One of the fears of quantum supremacy being achieved is that quantum computing could be used to easily crack the encryption currently used anywhere you use a password or to keep communications private, although it seems like we still have some time before this happens.
“The problem their machine solves with astounding speed has been very carefully chosen just for the purpose of demonstrating the quantum computer’s superiority,” Preskill says. It’s unclear how long it will take quantum computers to become commercially useful; breaking encryption — a theorized use for the technology — remains a distant hope. “That’s still many years out,” says Jonathan Dowling, a professor at Louisiana State University.