Locally stable sets with minimum cardinality

Abstract

The nonlocal set has received wide attention over recent years. Shortly before, Li and Wang arXiv:2202.09034 proposed the concept of a locally stable set: the only possible orthogonality preserving measurement on each subsystem is trivial. Locally stable sets present stronger nonlocality than those sets that are just locally indistinguishable. In this work, we focus on the constructions of locally stable sets in multipartite quantum systems. First, two lemmas are put forward to prove that an orthogonality-preserving local measurement must be trivial. Then we present the constructions of locally stable sets with minimum cardinality in bipartite quantum systems ${\mathbb{C}}^d\otimes {\mathbb{C}}^d$ $(d\ge 3)$ and ${\mathbb{C}}^{d_1}\otimes {\mathbb{C}}^{d_2}$ $(3\le d_1\le d_2)$. Moreover, for the multipartite quantum systems $({\mathbb{C}}^d{)}^{\otimes n}$ $(d\ge 2)$ and ${\otimes }_{i=1}^n{\mathbb{C}}^{d_i}$ $(3\le d_1\le d_2\le \cdots \le d_n)$, we also obtain $d+1$ and $d_n+1$ locally stable orthogonal states respectively. Fortunately, our constructions reach the lower bound of the cardinality on the locally stable sets, which provides a positive and complete answer to an open problem raised in arXiv:2202.09034 .

10 pages, 3 figures

References in corpus (6)

• Multipartite Nonlocality without Entanglement in Many Dimensions
• Quantum secret sharing based on local distinguishability
• Local distinguishability with preservation of entanglement
• Strong quantum nonlocality with entanglement
• Strong quantum nonlocality in $N$-partite systems
• $d$ locally indistinguishable maximally entangled states in ${\mathbb{C}}^d\otimes {\mathbb{C}}^d$