Determination of optimal chain coupling made by embedding in D-wave quantum annealer.

The qubits in a D-wave quantum annealer (D-wave QA) are designed on a Pegasus graph that is different from the structure of a combinatorial optimization problem. This situation requires embedding with the chains connected by ferromagnetic coupling J c between the qubits. Weak and strong J c values induce chain breaking and enforcement of chain energy, which reduce the accuracy of quantum annealing (QA) measurements, respectively. In addition, we confirmed that even though the D-wave Ocean package provides a default coupling J c default , it is not an optimal coupling J c optimal that maximizes the possible correct rate of QA measurements. In this paper, we present an algorithm how J c optimal with the maximum probability p for observing the possible lowest energy is determined. Finally, we confirm that the extracted J c optimal shows much better p than J c default in QA measurements of various parameters of frustrated and fully connected combinatorial optimization problems. The open code is available in https://github.com/HunpyoLee/OptimizeChainStrength. [ABSTRACT FROM AUTHOR]