A universal, memory-assisted entropic uncertainty relation

TL;DR

This paper introduces a universal memory-assisted entropic uncertainty relation that incorporates quantum correlations and discord, providing a more resilient and state-dependent bound applicable across various observables.

Contribution

It presents a new, universal entropic uncertainty relation that explicitly includes quantum discord and correlations, contrasting with previous entanglement-based relations.

Findings

Quantum discord often provides tighter uncertainty bounds than entanglement.

The relation is state-dependent and independent of specific observables.

Discord-based bounds are more resilient under quantum noise.

Abstract

We derive a new memory-assisted entropic uncertainty relation for non-degenerate Hermitian observables where both quantum correlations, in the form of conditional von Neumann entropy, and quantum discord between system and memory play an explicit role. Our relation is `universal', in the sense that it does not depend on the specific observable, but only on properties of the quantum state. We contrast such an uncertainty relation with previously known memory-assisted relations based on entanglement and correlations. Further, we present a detailed comparative study of entanglement- and discord-assisted entropic uncertainty relations for systems of two qubits -- one of which plays the role of the memory -- subject to several forms of independent quantum noise, in both Markovian and non-Markovian regimes. We thus show explicitly that, partly due to the ubiquity and inherent resilience of quantum discord, discord-tightened entropic uncertainty relations often offer a better estimate of the uncertainties in play.