Additivity of decoherence measures for multiqubit quantum systems

TL;DR

The paper introduces a new decoherence measure for multiqubit systems, demonstrating its additivity property, which simplifies error estimation in quantum computing designs, supported by exact spin-boson model calculations.

Contribution

It proposes a novel decoherence measure based on maximal norm deviation and proves its additivity for multiqubit systems, aiding quantum error analysis.

Findings

The measure accurately quantifies environment-induced deviations.

Additivity allows error estimation by summing single-qubit errors.

Exact calculations confirm the measure's effectiveness in spin-boson models.

Abstract

We introduce new measures of decoherence appropriate for evaluation of quantum computing designs. Environment-induced deviation of a quantum system's evolution from controlled dynamics is quantified by a single numerical measure. This measure is defined as a maximal norm of the density matrix deviation. We establish the property of additivity: in the regime of the onset of decoherence, the sum of the individual qubit error measures provides an estimate of the error for a several-qubit system. This property is illustrated by exact calculations for a spin-boson model.