Robust multipartite quantum correlations without complex encodings

TL;DR

This paper introduces a simple, experimentally friendly method to enhance the robustness of multipartite quantum entanglement against local noise by using local-unitary rotations, without requiring complex encodings.

Contribution

The authors propose a straightforward technique using local-unitary rotations to protect multipartite entanglement from local noise, achieving full robustness without additional qubits.

Findings

States with exponentially decaying entanglement become fully robust.

Resilience of quantum resources like entanglement and nonlocality is significantly improved.

Method is experimentally feasible and does not increase physical qubit overhead.

Abstract

One of the main challenges for the manipulation and storage of multipartite entanglement is its fragility under noise. We present a simple recipe for the systematic enhancement of the resistance of multipartite entanglement against any local noise with a privileged direction in the Bloch sphere. For the case of exact local dephasing along any given basis, and for all noise strengths, our prescription grants full robustness: Even states with exponentially decaying entanglement are mapped to states whose entanglement is constant. In contrast to previous techniques resorting to complex logical-qubit encodings, such enhancement is attained simply by performing local-unitary rotations before the noise acts. The scheme is therefore highly experimentally friendly, as it brings no overhead of extra physical qubits to encode logical ones. In addition, we show that, apart from entanglement, the resiliences of the relative entropy of quantumness and the usefulness as resources for practical tasks such as metrology and nonlocality-based protocols are equivalently enhanced.