Activation of entanglement from quantum coherence and superposition

TL;DR

This paper investigates the relationship between quantum coherence and entanglement, proving a no-go theorem for their interconversion and experimentally demonstrating entanglement activation within quantum coherence.

Contribution

It establishes a fundamental no-go theorem for entanglement activation from superposition and experimentally shows activation within quantum coherence.

Findings

Proves a no-go theorem for entanglement activation from superposition.

Demonstrates entanglement activation using a CNOT gate within quantum coherence.

Provides new insights into the interplay between coherence and entanglement.

Abstract

Quantum entanglement and coherence are two fundamental features of nature, arising from the superposition principle of quantum mechanics. While considered as puzzling phenomena in the early days of quantum theory, it is only very recently that entanglement and coherence have been recognized as resources for the emerging quantum technologies, including quantum metrology, quantum communication, and quantum computing. In this work we study the limitations for the interconversion between coherence and entanglement. We prove a fundamental no-go theorem, stating that a general resource theory of superposition does not allow for entanglement activation. By constructing a CNOT gate as a free operation, we experimentally show that such activation is possible within the more constrained framework of quantum coherence. Our results provide new insights into the interplay between coherence and entanglement, representing a substantial step forward for solving longstanding open questions in quantum information science.