###### Agcat –

# Google’s quantum computing breakthrough: Our new chip might soon outperform a supercomputer. Google’s Quantum AI Lab has shown off a new 72-qubit quantum processor called ‘Bristlecone’, which it says could soon achieve ‘quantum supremacy’ by outperforming a classical supercomputer on some problems. Quantum supremacy is a key milestone on the journey towards quantum computing. The idea is that if a quantum processor can be operated with low enough error rates, it could outperform a classical supercomputer on a well-defined computer science problem. Quantum computers are an area of huge interest because, if they can be built at a large enough scale, they could rapidly solve problems that cannot be handled by traditional computers. That’s why the biggest names in tech are racing ahead with….

Google’s Quantum AI Lab has shown off a new 72-qubit quantum processor called ‘Bristlecone’, which it says could soon achieve ‘quantum supremacy’ by outperforming a classical supercomputer on some problems. Quantum supremacy is a key milestone on the journey towards quantum computing. The idea is that if a quantum processor can be operated with low enough error rates, it could outperform a classical supercomputer on a well-defined computer science problem.

Quantum computers are an area of huge interest because, if they can be built at a large enough scale, they could rapidly solve problems that cannot be handled by traditional computers. That’s why the biggest names in tech are racing ahead with quantum computing projects: in January Intel announced its own 49-qubit quantum chip, for example. “We are cautiously optimistic that quantum supremacy can be achieved with Bristlecone,” said Julian Kelly, a research scientist at the Quantum AI Lab. “We believe the experimental demonstration of a quantum processor outperforming a supercomputer would be a watershed moment for our field, and remains one of our key objectives,” Kelly said — although he did not offer a timescale for this achievement.

If a quantum processor is to run algorithms beyond the scope of classical simulations, a large number of qubits are required, along with low error rates on readout and logical operations, such as single and two-qubit gates. Although researchers have yet to achieve quantum supremacy, Google thinks it can be demonstrated with 49 qubits, a circuit depth exceeding 40, and a two-qubit error below 0.5 percent.

Google said its new 72-qubit Bristlecone device uses the same scheme for coupling, control, and readout as its previous 9-qubit linear array. With the new processor, researchers are looking to achieve similar performance to the best error rates of the 9-qubit device, but now across all 72 qubits of Bristlecone. The 9-qubit device demonstrated low error rates for readout (one percent), single-qubit gates (0.1 percent) and most importantly two-qubit gates (0.6 percent) as its best result.

“We believe Bristlecone would then be a compelling proof-of-principle for building larger scale quantum computers,” Kelly said. However he added: “Operating a device such as Bristlecone at low system error requires harmony between a full stack of technology ranging from software and control electronics to the processor itself. Getting this right requires careful systems engineering over several iterations.”

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