Entanglement amplification between superposed detectors in flat and curved spacetimes

Abstract

We consider an entanglement harvesting protocol between two Unruh-deWitt detectors in quantum superpositions of static trajectories in the static de Sitter and thermal Minkowski spacetimes. We demonstrate for the first time that the spatial superposition of each detector's path allows entanglement to be harvested from the quantum field in regimes where it would be otherwise impossible for detectors on classical trajectories. Surprisingly, for detectors on sufficiently delocalised trajectories in a thermal bath, the amount of harvested entanglement grows with the temperature of the field, violating a no-go theorem derived by Simidzija et. al. (Phys. Rev. D 98, 085007). Furthermore, we discover that mutual information harvesting is inhibited by the presence of quantum interference between the superposed detector trajectories.

Harvesting entanglement from complex scalar and fermionic fields with linearly coupled particle detectors

“…Figure 4 shows the negativity as a function of both L and Ω. The region where it is possible to harvest entanglement, as well as the overall behaviour of N (2) presents differences when compared to what is seen in the literature for the ground-ground protocol for entanglement harvesting [15][16][17][18][19]. In the ground-ground case, negativity vanishes for sufficiently small values of ΩT to be zero for Ω below a certain threshold, while in the ground- excited case, we see that provided that the detectors are close enough (and definitely not spacelike separated [54]), they are able to get entangled.…”

“…This model has also been proven to capture the fundamental features of the light-matter interaction when exchange of angular momentum is not relevant [16,44,45]. In particular for our purposes, particle detectors have been used to study the entanglement structure of quantum fields through the protocol known as entanglement harvesting [15][16][17][18][19].…”

“…Now that we have introduced the interaction between one detector and the field, we will investigate the entanglement harvesting protocol [15][16][17][18][19]. In this protocol, instead of one, we must couple (at least) two particle detectors to the field.…”

“…Entanglement harvesting for detectors initially in their ground state has been extensively studied in the literature (see, among many others, [15][16][17][18][19][25][26][27][28][29]). Since many examples of the harvesting protocol with this initial state can be found in the literature, we will not show any particular example in this subsection.…”

“…A possible way to approach this problem is to quantify the amount of entanglement that can be extracted by local probes that couple to the field at different spacetime regions. In fact, the setup in which two localized probes couple to the vacuum of a quantum field theory to spacelike separated regions has become known as entanglement harvesting [15][16][17][18][19].…”