IBM has cast doubt over Google’s recent claim to have made a major breakthrough in quantum computing.

Google researchers this week claimed to have achieved a significant milestone with the creation of a quantum computer capable of surpassing traditional devices.

Tasks that would normally take some of the world’s most-advanced supercomputers 10,000 years to be completed can be tackled in just 200 seconds by Google’s Sycamore quantum processor. The results of Google’s tests were published in the scientific journal, Nature, and appear to have secured the tech giant’s position as the first to achieve “quantum supremacy”.

Commenting on the study, Google CEO Sundar Pichai said: “To demonstrate supremacy, our quantum machine successfully performed a test computation in just 200 seconds that would have taken the best-known algorithms in the most powerful supercomputers thousands of years to accomplish.

“We are able to achieve these enormous speeds only because of the quality of control we have over the qubits. Quantum computers are prone to errors, yet our experiment showed the ability to perform a computation with few enough errors at a large enough scale to outperform a classical computer.”

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Google’s success in this area follows “years of research and the dedication of many people,” according to Hartmut Neven, engineering director at Google’s quantum team. It also marks the beginning of an exciting new period for computing as the firm established how this technology can be applied and what its potential benefits will be in the long-term.

The technology giant also confirmed it will work closely with the research community and has open-sourced a range of tools to bring researchers around the world into the discussion to help identify new applications.

Google’s quantum supremacy claim, however, hasn’t been well received by everyone and is being hotly contested by a rival in the global technology sector.

But IBM has challenged Google’s research findings, suggesting that the company chose “one very specific” calculation for Sycamore to solve – one which had virtually “no practical applications”.

Additionally, researchers at IBM said that a classical computer is actually capable of completing the calculation within two-and-a-half days, rather than the 10,000 years claim that Google made previously.

“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,” IBM researchers said in a statement. “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.”

Responding to the claims, Google said its stated 10,000 years figure is based on simulations it conducted on IBM’s own Summit supercomputer, which is acknowledged as being the world’s fastest device.

What is Quantum Computing?

A ‘bit’ in classical computers stores information as a 0 or 1, whereas a quantum bit – also known as a ‘qubit’ – can be both 0 and 1 simultaneously, a property called superposition.

Essentially, this allows computational power to grow exponentially with every added qubit. In a video uploaded yesterday to explain this process, Google suggested that with 52 qubits, the Sycamore quantum computer is capable of exploring 10 million billion states at the same time.

“If you have two quantum bits, there are four possible states that you can put in superposition, and those grow exponentially,” Pichai explained. “With 333 qubits there are 2^333 computational states you can put in superposition, allowing a quantum computer to simultaneously explore a rich space of many possible solutions to a problem.”