Flow of quantum correlations in noisy two-mode squeezed microwave states

TL;DR

This paper experimentally investigates the robustness of quantum discord versus entanglement in noisy two-mode squeezed microwave states, revealing fundamental differences and implications for quantum communication security.

Contribution

It provides the first experimental verification of quantum discord's robustness in propagating microwave states under thermal noise and explores the flow of quantum correlations in noisy environments.

Findings

Quantum discord remains robust against thermal noise.

Entanglement exhibits sudden death under noise.

Difference between discord and entanglement relates to quantum key distribution security.

Abstract

We study nonclassical correlations in propagating two-mode squeezed microwave states in the presence of noise. We focus on two different types of correlations, namely, quantum entanglement and quantum discord. Quantum discord has various intriguing fundamental properties which require experimental verification, such as the asymptotic robustness to environmental noise. Here, we experimentally investigate quantum discord in propagating two-mode squeezed microwave states generated via superconducting Josephson parametric amplifiers. By exploiting an asymmetric noise injection into these entangled states, we demonstrate the robustness of quantum discord against thermal noise while verifying the sudden death of entanglement. Furthermore, we investigate the difference between quantum discord and entanglement of formation, which can be directly related to the flow of locally inaccessible information between the environment and the bipartite subsystem. We observe a crossover behavior between quantum discord and entanglement for low noise photon numbers, which is a result of the tripartite nature of noise injection. We demonstrate that the difference between entanglement and quantum discord can be related to the security of certain quantum key distribution protocols.