# Single-copy entanglement detection

## TL;DR

This paper introduces a new method for verifying quantum entanglement using a single copy of the state, significantly reducing the measurement requirements for large-scale quantum systems.

## Contribution

It formulates entanglement verification as a decision problem, enabling detection with high confidence from just one copy of the quantum state.

## Key findings

- Single-copy detection of entanglement in large quantum states
- High-confidence verification with one copy of 16-qubit and 24-qubit states
- Applicable to cluster states and ground states of local Hamiltonians

## Abstract

One of the main challenges of quantum information is the reliable verification of quantum entanglement. The conventional detection schemes require repeated measurement on a large number of identically prepared systems. This is hard to achieve in practice when dealing with large-scale entangled quantum systems. In this letter we develop a novel method by formulating verification as a decision procedure, i.e. entanglement is seen as the ability of quantum system to answer certain "yes-no questions". We show that for a variety of large quantum states even a single copy suffices to detect entanglement with a high probability by using local measurements. For example, a single copy of a $16$-qubit $k$-producible state or one copy of $24$-qubit linear cluster state suffices to verify entanglement with more than $95\%$ confidence. Our method is applicable to many important classes of states, such as cluster states or ground states of local Hamiltonians in general.