Experimental investigation of an eight-qubit unit cell in a superconducting optimization processor

TLDR

The chip’s architecture and control infrastructure were designed to enable adiabatic quantum optimization. The experiment used the chip’s flux qubits, tunable couplers, XY‑readout, programmable memory, and sparse control lines to measure the eight‑qubit unit cell’s success on random Ising spin‑glass problems as temperature varied. Experimental results on the superconducting eight‑qubit chip show successful solution of random Ising spin‑glass instances, agree with a quantum‑mechanical model coupled to a thermal bath, and reveal practical challenges toward scalable adiabatic quantum processors.

Abstract

A superconducting chip containing a regular array of flux qubits, tunable interqubit inductive couplers, an XY-addressable readout system, on-chip programmable magnetic memory, and a sparse network of analog control lines has been studied. The architecture of the chip and the infrastructure used to control it were designed to facilitate the implementation of an adiabatic quantum optimization algorithm. The performance of an eight-qubit unit cell on this chip has been characterized by measuring its success in solving a large set of random Ising spin glass problem instances as a function of temperature. The experimental data are consistent with the predictions of a quantum mechanical model of an eight-qubit system coupled to a thermal environment. These results highlight many of the key practical challenges that we have overcome and those that lie ahead in the quest to realize a functional large scale adiabatic quantum information processor.