Google鈥檚 new聽72-qubit quantum processor is the largest yet. Called Bristlecone, it was on 5 March at a meeting of the American Physical Society in Los Angeles.
The tech giant is racing rivals like IBM to demonstrate a quantum computer that can surpass the abilities of ordinary machines. This goal of 鈥�quantum supremacy鈥� is generally thought to require about 50 quantum bits, or qubits, and Google hopes to achieve it this year. However, quantum simulations on regular computers have continually raised that 50-qubit bar, leaving the finish line uncertain.
A successful quantum computer must also have low error rates to ensure its calculations are correct. Bristlecone is designed to mimic聽Google鈥檚 previous 9-qubit quantum computer, which聽had error rates聽of 0.6 per cent per two-qubit quantum logic gate.聽 It is thought that quantum supremacy requires an error rate per gate below 0.5 per cent.
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Google has聽not yet demonstrated Bristlecone鈥檚 abilities and it will likely go through several versions before it becomes a useful quantum computer. Julian Kelly, a research scientist at Google鈥檚 Quantum AI Lab, said in a that the research team is 鈥渃autiously optimistic that quantum supremacy can be achieved with Bristlecone.鈥�
at the University of Maryland in College Park says, 鈥�72 perfect qubits would definitely suffice to do something very interesting, but any real device is noisy and what it can actually do will depend on the details.鈥� He says Google鈥檚 blog post suggests they are聽focusing on the right issues, namely maintaining or improving error rates while scaling up.
鈥淭his 72-qubit processor is by all means an impressive technological feat,鈥� says of the University of South California, and聽in principle,聽Google鈥檚 quantum chip should be powerful enough to achieve quantum supremacy. But don鈥檛 count out supercomputers just yet, he says.聽鈥淭he algorithmic capabilities of standard computers keep evolving as well and it is too early to tell in my view who would eventually win this race.鈥�
