W-like bound entangled states and secure key distillation

TL;DR

This paper constructs multipartite W-type bound entangled states that are PPT under any bipartition and demonstrates methods for distilling secure keys from these states, advancing quantum cryptography.

Contribution

It introduces a new class of W-type bound entangled states with PPT properties and proposes two methods for secure key distillation from them.

Findings

States are PPT under any (N-1)|1 partition.

Secure key can be distilled using local filtering.

A novel random key distillation scheme is proposed.

Abstract

We construct multipartite entangled states with underlying W-type structure satisfying positive partial transpose (PPT) condition under any (N-1)|1 partition. Then we show how to distill N-partite secure key form the states using two different methods: direct application of local filtering and novel random key distillation scheme in which we adopt the idea form recent results on entanglement distillation. Open problems and possible implications are also discussed.