Harvesting Contextuality from the Vacuum

TL;DR

This paper introduces a protocol for harvesting quantum contextuality from the vacuum using Unruh-DeWitt models, demonstrating that gapless systems can extract contextuality and exploring the tradeoffs with entanglement.

Contribution

It presents the concept of contextuality harvesting from the vacuum, analyzes Unruh-DeWitt models for this purpose, and introduces new criteria for genuine harvesting of contextuality.

Findings

Gapless systems can harvest contextuality with suitable measurements.

Harvested contextuality can be larger than magic in certain regimes.

Tradeoffs exist between harvested contextuality and entanglement.

Abstract

Quantum contextuality is the notion that certain measurement scenarios do not admit a global description of their statistics and has been implicated as the source of quantum advantage in a number of quantum information protocols. It has been shown that contextuality generalizes the concepts of non-local entanglement and magic, and is an equivalent notion of non-classicality to Wigner negativity. In this paper, the protocol of contextuality harvesting is introduced and it is shown that Unruh-DeWitt models are capable of harvesting quantum contextuality from the vacuum of a massless scalar quantum field. In particular, it is shown that gapless systems can be made to harvest contextuality given a suitable choice of measurements. The harvested contextuality is also seen to behave similarly to harvested magic and can be larger in magnitude for specific parameter regimes. An Unruh-DeWitt qubit-qutrit system is also investigated, where it is shown that certain tradeoffs exist between the harvested contextuality of the qutrit and the harvested entanglement between the systems, and that there are harvesting regimes where the two resources can both be present. Some of the tools of contextuality, namely the contextual fraction, are also imported and used as general harvesting measures for any form of contextuality, including non-local entanglement and magic. Additionally, new criteria for genuine harvesting are put forward that also apply to individual systems, revealing new permissible harvesting parameter regimes.