Quantum Leap

In the race to demonstrate quantum supremacy, Google recently made headway with the introduction of Bristlecone, the largest-ever quantum processor at 72 qubits. It was presented last month at a meeting of the American Physical Society, and the company is “cautiously optimistic” that it will be a key development toward demonstrating a proof-of-concept quantum computer that can outperform today’s supercomputers.

While quantum supremacy has not yet been achieved, it is generally believed to be possible with 49 qubits. However, a low error rate is also an essential objective — and not a trivial task. Google’s earlier 9-qubit linear array processor demonstrated an error rate as low as 0.6 percent per 2-qubit gate. The benchmark goal of 0.5 percent will require careful systems engineering to integrate a full range of software and control electronics with the processor itself.