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 that 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 cannot.
Highlights
Entanglement is the strongest among quantum correlations, rooted in the structurally non-local behavior of quantum mechanics
The quantum-enhanced performances of technological tasks can be achieved by exploiting other quantum resources than solely entanglement [9,10], in the following, we focus on quantum protocols that require entanglement and are implemented by means of systems consisting of many identical particles
In the second part of the work, we examine different approaches to indistinguishable particle entanglement alternative to mode entanglement; using established results provided by the literature, we discuss in detail, through explicit examples, how these approaches fail to properly identify quantum resources as a consequence of their inability to consistently cope with the locality issue
Summary
Entanglement is the strongest among quantum correlations, rooted in the structurally non-local behavior of quantum mechanics. It is a fundamental resource in most quantum information protocols and processes, as shown in actual applications using different physical settings, e.g., in quantum optics and atomic and molecular physics [1,2,3,4,5,6]. Many-body systems are more treated by adopting the so-called “secondquantization” approach; within this framework, the notions of non-locality and entanglement valid for distinguishable particles can be generalized to hold in systems made of identical constituents, in a way applicable to all physical situations. We shall analyze two quantum protocols, one in quantum metrology and the other one in teleportation, and describe in detail how for identical particle systems, non-locality and entanglement can be used to reach accuracies beyond those obtainable with classical methods
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