Universal detection of entanglement in two-qubit states using only two copies

TL;DR

This paper introduces a resource-efficient protocol for detecting entanglement in unknown two-qubit states using only two copies and a single post-selection measurement, enabling complete state identification with minimal resources.

Contribution

The authors present a novel entanglement detection protocol that uses weak values and two copies, requiring only a single measurement setting for complete state identification.

Findings

Protocol successfully detects entanglement with minimal resource use.

Complete state identification achieved with a single post-selection measurement.

Robustness demonstrated against errors in global interactions.

Abstract

We revisit the problem of detection of entanglement of an unknown two-qubit state using minimal resources. Using weak values and just two copies of an arbitrary two-qubit state, we present a protocol where a post selection measurement in the computational basis provides enough information to identify if the state is entangled or not. Our protocol enables complete state identification with a single-setting post selection measurement on two copies of the state. It follows that by restricting to pure states, the global interaction required for determining the weak values can be realized by local operations. We further show that our protocol is robust against errors arising from inappropriate global interactions applied during weak value determination.