Experimental analysis of decoherence of quantumness in a continuous variables bi-partite entangled system

TL;DR

This paper experimentally investigates how propagation losses in a Gaussian channel affect bipartite Gaussian entangled states, showing they retain quantum discord and entanglement properties even under strong decoherence, enabling long-distance quantum teleportation.

Contribution

It provides experimental evidence that certain continuous-variable entangled states maintain quantum correlations despite decoherence, supporting their use in long-distance quantum communication.

Findings

States remain entangled despite strong decoherence

Quantum discord persists beyond entanglement loss

Potential for quantum teleportation over infinite Gaussian channels

Abstract

Quantum properties are soon subject to decoherence once the quantum system interacts with the classical environment. In this paper we experimentally test how propagation losses, in a Gaussian channel, affect the bi-partite Gaussian entangled state generated by a sub-threshold type-II optical parametric oscillator (OPO). Experimental results are discussed in terms of different quantum markers, as teleportation fidelity, quantum discord and mutual information, and continuous variables (CV) entanglement criteria. To analyse state properties we have retrieved the composite system covariance matrix by a single homodyne detector. We experimentally found that, even in presence of a strong decoherence, the generated state never disentangles and keeps breaking the quantum limit for the discord. This result proves that the class of CV entangled states discussed in this paper would allow, in principle, to realize quantum teleportation over an infinitely long Gaussian channel.