Location
QNC 2101
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Adam Teixido-BonfillÌý| Applied Mathematics, University of À¶Ý®ÊÓƵ
Title
Harvesting entanglement from quantum fields: from theory to proposed superconducting implementations
Abstract
This thesis studies entanglement harvesting, a relativistic quantum information protocol where quantum systems, called detectors, become entangled by locally interacting with a quantum field. Such detectors can entangle even when causally disconnected, implying that the entanglement is extracted (harvested) from the field. While this effect has not yet been observed experimentally, various implementations have been proposed, including in superconducting circuits.
We begin by analyzing entanglement harvesting with detectors that couple to the derivative of the field amplitude. This particular coupling is relevant to light-matter interaction and is naturally realized in superconducting circuits. We study detectors in causal contact, for which entanglement has two sources: communication via the field and pre-existing correlations in the field. We show how these two sources interfere, boosting or canceling the final entanglement. We then extend our analysis to more general detector models, finding that entanglement harvesting is always dominated, at leading order, by transversal interactions with respect to the initial state. Beyond leading order, we explore how strong longitudinal couplings can suppress harvesting.
Finally, we propose a variable energy gap detector model and connect it to existing superconducting circuit implementations. We then use this model to study harvesting in both causally disconnected and causally connected scenarios. Our results indicate that the energy gap variations hinder harvesting for causally disconnected detectors, but do not prevent entanglement harvesting for causally connected detectors. These results show the potential for entanglement harvesting in the lab, helping to pave the way to its experimental demonstration in superconducting circuits.