Google has developed a new quantum processor called Bristlecone that it hopes will be instrumental in building a quantum computer capable of solving real-world problems. At the American Physical Society meeting in Los Angeles where the chip was unveiled, Google said the purpose of its gate-based superconducting system is to provide a testbed for research into system error rates and scalability of its qubit technology, along with applications in quantum simulation, optimization, and machine learning.
"In order for a quantum processor to be able to run algorithms beyond the scope of classical simulations, it requires not only a large number of qubits. Crucially, the processor must also have low error rates on readout and logical operations, such as single and two-qubit gates," Google said.
Bristlecone is based on Google's previous 9-qubit linear technology, which demonstrated low error rates for reader, single qubit gates, and two-qubit rates. It's been scaled to a square of 72 qubits, a size Google chose to "demonstrate quantum supremacy" in future applications. Google also says it was motivated by its goal of facilitating quantum algorithm development on actual hardware.
"We calculate quantum supremacy can be comfortably demonstrated with 49 qubits, a circuit depth exceeding 40, and a two-qubit error below 0.5 percent. 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," Google added. "We are looking to achieve similar performance to the best error rates of the 9-qubit device, but now across all 72 qubits of Bristlecone."
From Google's perspective, Bristlecone offers a compelling proof-of-principle for building larger scale quantum computers. In order to achieve the low error rate that the chip is capable of, it requires that all parts play nice together, from the software and control electronics, to the actual processor.
Quantum supremacy, which is the ultimate goal here, is the ability to run certain algorithms faster than a traditional computer. Bristlecone is a potential big step in that direction.