Robust Micro-Macro Entangled States

TL;DR

This paper investigates the fragility of micro-macro entangled states to environmental noise, identifying symmetric states as most robust and analyzing how macroscopicity affects entanglement robustness, aiding quantum information and classical transition understanding.

Contribution

It provides a detailed analysis of noise effects on micro-macro entangled states, highlighting symmetric states as optimal for robustness and quantifying how macroscopicity impacts entanglement stability.

Findings

Symmetric micro-macro entangled states are most robust to single particle noise.

Robustness decreases quadratically with macroscopicity.

A regime exists where states are both robust and macroscopically entangled.

Abstract

Bipartite entangled states between a qubit and macroscopically distinct states of a mesoscopic system, known as micro-macro entangled states, are emerging resources for quantum information processing. One main challenge in generating such states in the lab is their fragility to environmental noise. We analyze this fragility in detail for single particle noise by identifying what factors play a role in the robustness and quantifying their effect. There is a trade-off between the macroscopicity of a micro-macro entangled state and the robustness of its bipartite entanglement to environmental noise. We identify symmetric micro-macro entangled states as the most robust states to single particle noise. We show that the robustness of bipartite entanglement of such states to single particle noise decreases as the second order of macroscopicity, which identifies a regime where the bipartite entangled state is both robust and macroscopic. Our result is a step towards retaining quantum characteristics on large scales and experimental realization of micro-macro entangled spin states and their use for connecting separated qubits. Moreover, it advances our understanding of quantum to classical transition.