Duality between imperfect resources and measurements for propagating entanglement in networks

TL;DR

This paper introduces measurement-based strategies for entanglement propagation in quantum networks, showing that certain protocols can enhance entanglement sharing even in noisy conditions, with unidirectional schemes often outperforming bidirectional ones.

Contribution

It presents a novel entanglement propagation method using unsharp measurements, analyzing the effects of noise and measurement direction on entanglement sharing in quantum networks.

Findings

Post-selected measurements can increase entanglement shareability under noise.

Unidirectional protocol reduces noise impact on monogamy score faster.

Nonmaximally entangled states can outperform maximally entangled states in certain noise regimes.

Abstract

We propose a measurement-based entanglement propagation strategy for networks in which all nodes except two are initially occupied by a suitably chosen single-qubit system and the two nodes share a bipartite noisy entangled state. The connections between the sites are established using unsharp two-qubit measurements. When only a single node performs measurements, we refer to it as a unidirectional protocol while when both parts of the initial entangled states perform measurements, we call it a bidirectional scheme. When the measurement outcome is post-selected, we demonstrate that in the presence of a local amplitude damping channel acting on a single site, entanglement shareability, as measured by the monogamy score, of the resulting state after measurement can be higher for all values of the strength of the noise than that of the scenario without noise. We observe that irrespective of the channel, there exists a range of unsharpness parameter where a higher monogamy score may be obtained starting from the initial nonmaximally entangled states than from the initial maximally entangled state. We report that the effect of noise on the average monogamy score entered from the resource state may be reduced faster with the unidirectional protocol than with the bidirectional one.