Reducing multi-qubit interactions in adiabatic quantum computation without adding auxiliary qubits. Part 2: The "split-reduc" method and its application to quantum determination of Ramsey numbers

TL;DR

This paper introduces the 'split-reduc' method to minimize multi-qubit interactions in adiabatic quantum computation, enabling the use of full device capacity without auxiliary qubits, demonstrated through Ramsey number calculations.

Contribution

The paper presents a novel 'split-reduc' technique that reduces multi-qubit interactions, allowing full utilization of quantum annealing hardware for complex computations.

Findings

The method can determine R(16,2) and R(4,3) in under 10 minutes.

It eliminates the need for auxiliary qubits in quantum annealing.

Enables larger Ramsey number computations on existing hardware.

Abstract

Quantum annealing has recently been used to determine the Ramsey numbers R(m,2) for 3 < m < 9 and R(3,3) [Bian et al. (2013) PRL 111, 130505]. This was greatly celebrated as the largest experimental implementation of an adiabatic evolution algorithm to that date. However, in that computation, more than 66% of the qubits used were auxiliary qubits, so the sizes of the Ramsey number Hamiltonians used were tremendously smaller than the full 128-qubit capacity of the device used. The reason these auxiliary qubits were needed was because the best quantum annealing devices at the time (and still now) cannot implement multi-qubit interactions beyond 2-qubit interactions, and they are also limited in their capacity for 2-qubit interactions. We present a method which allows the full qubit capacity of a quantum annealing device to be used, by reducing multi-qubit and 2-qubit interactions. With our method, the device used in the 2013 Ramsey number quantum computation could have determined R(16,2) and R(4,3) with under 10 minutes of runtime.