Google claims it has achieved a breakthrough in quantum computing research, saying an experimental quantum processor has completed a calculation in just a few minutes that would take a traditional supercomputer thousands of years.
The findings, published Wednesday in the scientific journal Nature, show that "quantum speedup is achievable in a real-world system and is not precluded by any hidden physical laws," the researchers wrote.
The announcement comes one month after it initially leaked, when Google’s paper was accidentally published early.
Quantum computing relies on quantum bits, or qubits, which can register data values of zero and one simultaneously. Big tech companies including Google, Microsoft, IBM and Intel are avidly pursuing the technology.
A bit in a classical computer can store information as a 0 or 1. A quantum bit—or qubit—can be both 0 and 1 at the same time, a property called superposition. So if you have two quantum bits, there are four possible states that you can put in superposition, and those grow exponentially. With 333 qubits there are 2^333, or 1.7x10^100—a Googol—computational states you can put in superposition, allowing a quantum computer to simultaneously explore a rich space of many possible solutions to a problem.
Google says that its 54-qubit Sycamore processor was able to perform a calculation in 200 seconds that would have taken the world’s most powerful supercomputer 10,000 years. That would mean the calculation, which involved generated random numbers, is essentially impossible on a traditional, non-quantum computer.
Google's findings, however, are already facing pushback from other industry researchers. IBM quickly took issue with Google's claim that it had achieved "quantum supremacy," a term that refers to a point when a quantum computer can perform a calculation that a traditional computer can't complete within its lifetime. IBM researchers say that Google underestimated the conventional supercomputer, called Summit, and said it could actually do the calculation in 2.5 days.
Whether or not Google has achieved "quantum supremacy" or not may matter to competitors.
"For those of us working in science and technology, it’s the “hello world” moment we’ve been waiting for—the most meaningful milestone to date in the quest to make quantum computing a reality. But we have a long way to go between today’s lab experiments and tomorrow’s practical applications; it will be many years before we can implement a broader set of real-world applications," said Google CEO Sundar Pichai.
Pichai added that Google's breakthrough brings us one step closer to applying quantum computing to—for example—design more efficient batteries, create fertilizer using less energy, and figure out what molecules might make effective medicines.
Those applications are still many years away and we are committed to building the error-corrected quantum computer that will power these discoveries.
Pichai believes that quantum computing will be a great complement to the work we do (and will continue to do) on classical computers.
"For this demonstration, we congratulate the team at Google," said Rich Uhlig, managing director of Intel Labs. However, he said that the attention should be now turned to the steps it will take to build a system that will enable us to address intractable challenges — in other words, to demonstrate quantum practicality," he added.
Intel researchers used our high-performance quantum simulator to predict the point at which a quantum computer could outpace a supercomputer in solving an optimization problem called Max-Cut. They chose Max-Cut as a test case because it is widely used in everything from traffic management to electronic design, and because it is an algorithm that gets exponentially more complicated as the number of variables increases.
In Intel's study, the researchers compared a noise-tolerant quantum algorithm with a state-of-the art classical algorithm on a range of Max-Cut problems of increasing size. After extensive simulations, Intel's research suggests it will take at least hundreds, if not thousands, of qubits working reliably before quantum computers will be able to solve practical problems faster than supercomputers.
"In other words, it may be years before the industry can develop a functional quantum processor of this size, so there is still work to be done," Uhlig said.