Lower and upper bounds for unilateral coherence and applying them to the entropic uncertainty relations

TL;DR

This paper introduces a novel, simplified method using quantum coherence to derive entropic uncertainty relations with quantum memory, providing tighter bounds and new insights into measurement predictability in quantum systems.

Contribution

It presents a new approach based on quantum coherence for obtaining entropic uncertainty relations with quantum memory, offering simpler calculations and tighter bounds than existing methods.

Findings

Derived upper bounds on unilateral coherence for given states.

Identified which bounds are tighter for specific states.

Established a nontrivial upper bound on entropy sums with quantum memory.

Abstract

The uncertainty principle sets a bound on our ability to predict the measurement outcomes of two incompatible observables which are measured on a quantum particle simultaneously. In quantum information theory, the uncertainty principle can be formulated in terms of the Shannon entropy. Entropic uncertainty bound can be improved by adding a particle which correlates with the measured particle. The added particle acts as a quantum memory. In this work, a method is provided for obtaining the entropic uncertainty relations in the presence of a quantum memory by using quantum coherence. In the method, firstly, one can use the quantum relative entropy of quantum coherence to obtain the uncertainty relations. Secondly, these relations are applied to obtain the entropic uncertainty relations in the presence of a quantum memory. In comparison with other methods this approach is much simpler. Also, for a given state, the upper bounds on the sum of the relative entropies of unilateral coherences are provided, and it is shown which one is tighter. In addition, using the upper bound obtained for unilateral coherence, the nontrivial upper bound on the sum of the entropies for different observables is derived in the presence of a quantum memory.