What just happened? In 2019, Google’s Sycamore quantum computer achieved a so-called quantum supremacy record by completing a specific task in 200 seconds that would take a classical supercomputer 10,000 years. There was some controversy surrounding the feat, but overall, Google’s claim has stood the test of time — until now. Last month, a company called Quantinuum said it had reached a threshold of error-correction performance that many thought was years away.
A new 56-qubit H2-1 computer has made Google’s Sycamore quantum computer 100 times faster than its predecessor in the realm of ‘quantum superiority’.
That title now belongs to a computer company called Quantinuum, which ran multiple experiments on its quantum computer between January and June 2024. The company claims its machine has reached a threshold of error-correction performance that many experts thought would be years away.
The company published its findings last month in a study uploaded to the preprint database arXiv. The study has not yet been peer-reviewed.
Quantinuum claims to have demonstrated significant performance improvements using its Random Circuit Sampling algorithm, achieving an estimated linear cross entropy benchmark (XEB) score of ~0.35, over 100x better than previous demonstrations.
According to Quantinuum, the H2-1 configured with 32 physical qubits supported the creation of four highly reliable logical qubits that performed “better than break-even” – a key step toward fault-tolerant quantum computing. This means that the logical qubits are more reliable than the physical qubits that compose them, a crucial threshold for practical quantum error correction.
Furthermore, the error rates of logic circuits were found to be up to 800 times lower than the corresponding error rates of physical circuits. According to Quantinuum, no other quantum computing company has come close to that.
Error correction allows quantum computers to perform longer and more complex calculations by protecting quantum information from noise and decoherence. Quantum computing typically has much higher error rates than classical computing; current state-of-the-art quantum computers exhibit error rates ranging from 1% to 0.1%.
Google’s Sycamore quantum computer has 53 qubits and was first introduced in 2019. This computer completed a specific task in 200 seconds and recorded an XEB result of about 0.002. According to Google, it would have taken the world’s most advanced classical supercomputer, Summit, about 10,000 years to complete the task.
In short, it achieved a major milestone in quantum computing, known as quantum supremacy. IBM later claimed that the task would take just 2.5 days on a classical system like Summit.
But Ilyas Khan, founder and chief product officer of Quantinuum, seems to accept Sycamore’s achievement. “When Google released details of their ‘quantum supremacy’ experiment in late 2019, Sundar Pichai, their CEO, published a blog post that has stood the test of time regarding the significance of the milestone achieved then,” he said.
Quantinuum’s work “raises that bar to a place where we are now clearly operating in a place that has been long awaited. A place where classical supercomputers simply cannot compete and where the computational task is measurable and relevant.”