Google announced last week that it had overcome a major challenge in quantum computing, demonstrating a processor that solved in 5 minutes a problem that would take conventional computers an eternity.
The mathematical problem on which Google claims to have achieved so-called “quantum supremacy” has no practical application. Nevertheless, the company hopes that the technology will find important applications in chemistry, medicine, materials science, or even artificial intelligence.
Others, of course, believe that today’s quantum processors are too small and delicate to have practical applications, and that the promises of a “quantum revolution” are a bubble that will soon burst.
The latest achievement presented in the journal “Nature” (“Google Announces Solution to a Big Problem in Quantum Computing“) concerns the Willow processor (“Willow”) which includes 105 “qubits”, the equivalent of bits in quantum computers, but which have the strange ability to be in the states “0” and “1” at the same time.
Qubits are notorious for their instability, as they are affected by even the slightest increases in temperature or by subatomic particles falling from space. This creates errors, which inevitably multiply as the system grows.
And yet, Google claims to have found a way to connect Willow’s qubits so that the error rate decreases as the qubits increase. The solution lies in the use of groups of “spare” physical qubits that act as single “logical” qubits with automatic error correction.
The results this time seem convincing, in contrast to previous Google announcements that were ultimately refuted. In 2019, IBM shot down the company’s claim that a quantum chip had solved a problem that would have taken a classical computer 10,000 years, showing that it could be solved in two and a half days using different technical assumptions for a classical system.
In a company blog post, Google said it had taken those points into account in its new estimates. Even under theoretically ideal conditions, it said, a classical computer would take a billion years to reach the result achieved by the new processor. The company acknowledges, however, that it still has a long way to go, as a practical quantum computer is estimated to require hundreds of thousands or millions of qubits.
