Entanglement and non-locality in quantum protocols with identical particles

TL;DR

This paper clarifies the role of entanglement and non-locality in quantum protocols involving identical particles, emphasizing the importance of mode entanglement over particle-based notions to avoid paradoxes.

Contribution

It demonstrates that mode entanglement, not particle entanglement, is fundamental in quantum protocols with identical particles, resolving conceptual debates.

Findings

Mode entanglement is essential for quantum protocols with identical particles.

Inconsistencies arise when entanglement is attributed to particles rather than modes.

Orthogonal modes can be addressed, unlike identical particles, affecting protocol design.

Abstract

We study the role of entanglement and non-locality in quantum protocols that make use of systems of identical particles. Unlike in the case of distinguishable particles, the notions of entanglement and non-locality for systems whose constituents cannot be distinguished and singly addressed are still debated. We clarify why the only approach that avoids incongruities and paradoxes is the one based on the second quantization formalism whereby it is the entanglement of the modes that can be populated by the particles what really matters and not the particles themselves. Indeed, by means of a metrological and of a teleportation protocol, we show that inconsistencies arise in formulations that force entanglement and non-locality to be properties of the identical particles rather than of the modes they can occupy. The reason resides in the fact that orthogonal modes can always be addressed while identical particles can not.