Quantum discord for a two-parameter class of states in $2 \otimes d$ quantum systems

TL;DR

This paper derives an analytical expression for quantum discord in a specific class of two-parameter states in 2 by d quantum systems, expanding understanding beyond two-qubit states and highlighting differences among quantum correlation measures.

Contribution

It extends quantum discord evaluation to 2 by d systems and provides explicit formulas for a two-parameter class of states, comparing different quantum correlations.

Findings

Quantum discord is explicitly calculated for certain 2 by d states.

Different quantum correlation measures are shown to be conceptually distinct.

Comparison reveals non-equivalence of quantum discord, classical correlation, and entanglement.

Abstract

Quantum discord witnesses the nonclassicality of quantum states even when there is no entanglement in these quantum states. This type of quantum correlation also has some interesting and significant applications in quantum information processing. Quantum discord has been evaluated explicitly only for certain class of two-qubit states. We extend the previous studies to $2 \otimes d$ quantum systems and derive an analytical expression for quantum discord for a two-parameter class of states for $d \geq 3$. We compare quantum discord, classical correlation, and entanglement for qubit-qutrit systems to demonstrate that different measures of quantum correlation are not identical and conceptually different.