Efficient criteria of quantumness for a large system of qubits

TL;DR

This paper introduces a new quantumness measure called the accessibility index for large qubit systems, demonstrating its effectiveness on a quantum annealer and aiding the assessment of quantum coherence in complex systems.

Contribution

It proposes a novel, dimensionless quantumness criterion for large quantum systems and applies it to a real quantum annealing device to evaluate its quantum nature.

Findings

The accessibility index effectively characterizes the quantumness of large systems.

D-Wave One operates within the quantum domain according to this measure.

The criterion can be used for large-scale quantum system evaluation.

Abstract

In order to model and evaluate large-scale quantum systems, e.g. quantum computer and quantum annealer, it is necessary to quantify the ``quantumness" of such systems. In this paper, we discuss the dimensionless combinations of basic parameters of large, partially quantum coherent systems, which could be used to characterize their degree of quantumness. Based on analytical and numerical calculations, we suggest one such number for a system of qubits undergoing adiabatic evolution, i.e., the accessibility index. Applying it to the case of D-Wave One superconducting quantum annealing device, we find that its operation as described falls well within the quantum domain.