One of the quantum computers used by Google. (Google Quantum AI)While we call these devices quantum computers, they're more like prototypes of what quantum computers can be: At present they require super-specific, extreme conditions to operate in, and struggle to stay stable and error-free.
Despite those limitations, their computing potential is becoming more impressive all the time.
The latest system run by Google has a total of 70 operational qubits – the quantum equivalents of classical bits that can represent 1, or 0, or both at the same time, potentially allowing for certain calculations to be performed at astonishing speeds.
Specifically, the team used a complex, synthetic benchmark called random circuit sampling, which is exactly what it sounds like – taking readings from randomly generated quantum processes.
This maximizes the speed of critical actions, reducing the risk of outside noise destroying the calculation. They then estimated how long it would take existing supercomputers to run the same sums.
"We conclude that our demonstration is firmly in the regime of beyond-classical quantum computation," write the researchers in their recent paper.
The Frontier supercomputer, currently the most powerful computer in the world, would take a little over 47 years to crunch the same numbers, the researchers suggest, whereas the Sycamore quantum computer managed it in mere seconds.
A group including Google engineers did something similar in 2019, with 53 qubits. Then, as now, there's a debate to be had about how useful and practical these particular simulations are, and how fair (or otherwise) it is to compare supercomputer performance to what has been managed here.
Nevertheless, the Google team is clear in its claims that this demonstrates quantum supremacy: the idea that quantum computers really can deal with processes above and beyond anything that even the fastest classical computers can cope with.
The new experiments also tell us more about how quantum noise – the inherent uncertainty and fragility in a quantum computer as it operates in the fuzzy landscape of probabilities – can have an impact on processes as they're running, and in some cases lead to new phases (or states) in a quantum system.
Working through this noise to correctly record qubit states is essential in getting quantum computers functioning properly, and we've seen scientists try and tackle the problem in a variety of ways in the past.
According to Steve Brierley, chief executive at quantum company Riverlane in the UK, these latest experiments represent another "major milestone" in quantum computing research.
"The squabbling about whether we had reached, or indeed could reach, quantum supremacy is now resolved," Brierley told The Telegraph.
A paper on the new research is available on arXiv but has yet to be peer reviewed.
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