Stronger quantum supremacy

 On arxiv today: Strong quantum computational advantage using a superconducting quantum processor, by the group of Jian-Wei Pan at USTC.

This preprint reports a large 66 superconducting transmon qubit quantum processor, with performance similar to Google's Sycamore processor.  The random circuit sampling protocol is used to demonstrate a quantum computational advantage with 56 qubits (c.f. the previous 53 qubit Google experiment). More measurements are taken per random circuit (19 million samples vs 3 million) to obtain a higher cross entropy benchmarking fidelity (9 sigma rejection of uniform sampling vs 5 sigma). Because the difficulty of classical simulation increases exponentially with the number of qubits, this small increase in the device size incurs a 2-3 orders of magnitude-increased cost of classically simulating the circuit.

This is a significant breakthrough - Google no longer has a monopoly on large scale programmable superconducting quantum circuits!

Edit: Today the USTC team released another preprint reporting an upgraded and programmable Gaussian boson sampling experiment!