Quantum Supremacy: Benchmarking the Sycamore Processor

The promise of quantum computers is that certain computational tasks might be executed exponentially faster on a quantum processor than on a classical processor. A fundamental challenge is to build a high-fidelity processor capable of running quantum algorithms in an exponentially large computational space. Here we report the use of a processor with 53 programmable superconducting qubits. In our Sycamore processor, each qubit interacts with four neighbors in a rectangular lattice using tunable couplers. A key systems engineering advance of this device is achieving high-fidelity single- and two-qubit operations, not just in isolation but also while performing a realistic computation with simultaneous gate operations across the entire processor. We benchmark the Sycamore processor using cross-entropy benchmarking, a scalable method to evaluate system performance. Our largest system benchmarks feature circuits that are intractable for classical hardware, culminating in the demonstration of quantum supremacy. Furthermore, the fidelities from full-system benchmarks agree with what we predict from individual gate and measurement fidelities, verifying the digital error model and presenting a path forward to quantum error correction.

Nature 574, 505-510 (2019)