The power of symmetric extensions for entanglement detection

TL;DR

This paper advances the understanding of symmetric extension criteria for entanglement detection, providing bounds on noise perturbations, complexity estimates, and methods to approximate separability for quantum states.

Contribution

It introduces new bounds on perturbations needed to destroy entanglement and estimates the complexity of separability problems using symmetric extensions.

Findings

Perturbation of order O(1/N) suffices to destroy entanglement in N symmetric extension states.

Minimum local noise for PPT symmetric extension states decreases as O(1/N^2).

Provides bounds on complexity and error estimates for approximating separable states.

Abstract

In this paper, we present new progress on the study of the symmetric extension criterion for separability. First, we show that a perturbation of order O(1/N) is sufficient and, in general, necessary to destroy the entanglement of any state admitting an N Bose symmetric extension. On the other hand, the minimum amount of local noise necessary to induce separability on states arising from N Bose symmetric extensions with Positive Partial Transpose (PPT) decreases at least as fast as O(1/N^2). From these results, we derive upper bounds on the time and space complexity of the weak membership problem of separability when attacked via algorithms that search for PPT symmetric extensions. Finally, we show how to estimate the error we incur when we approximate the set of separable states by the set of (PPT) N -extendable quantum states in order to compute the maximum average fidelity in pure state estimation problems, the maximal output purity of quantum channels, and the geometric measure of entanglement.