Classical extension of quantum-correlated separable states

TL;DR

This paper explores how separable quantum states can be extended classically in higher dimensions, revealing that larger classical extensions correspond to higher discord in the original states, especially in low-dimensional systems.

Contribution

It introduces an optimal classical extension framework for separable states and analyzes the relationship between extension dimension and quantum discord in two-qubit systems.

Findings

Larger classical extensions lead to higher discord in original states.

Maximum discord separable states have specific classical extensions.

The study focuses on low-dimensional quantum systems.

Abstract

Li and Luo [Phys. Rev. A 78 (2008), 024303] discovered a remarkable relation between discord and entanglement. It establishes that all separable states can be obtained via reduction of a classicaly-correlated state "living" in a space of larger dimension. Starting from this result, we discuss here an optimal classical extension of separable states and explore this notion for low-dimensional systems. We find that the larger the dimension of the classical extension, the larger the discord in the original separable state. Further, we analyze separable states of maximum discord of two qubits, and their associated classical extensions.