Sabotaging the harvesting of correlations from quantum fields

Abstract

We study the non-perturbative harvesting of classical and quantum correlations between two parties coupled to a quantum field. First, we consider a scenario with an arbitrary number of two-level systems that couple to a quantum field locally in time. Then, we study the impact of the presence of additional detectors (interlopers) on the ability for two target detectors (Alice and Bob) to acquire correlations through their interaction with the field. We analyze the harvesting of different correlation measures in this non-perturbative regime and we demonstrate that even a single interloper can completely sabotage all correlation harvesting between Alice and Bob by acting on the causal past of one of them. Specifically, we show that the interloper is able to interact with the field so that the field itself 'floods' one of the parties with entropy. This prevents Alice and Bob from acquiring any correlations. Furthermore, we show that this kind of attack cannot be defended against.

Channel capacity of relativistic quantum communication with rapid interaction

“…Consequently, this proves that with shared entanglement as a resource, the entanglementassisted quantum channel capacity, denoted Q ea (E), for delta-coupling model can attain its minimum value of 1/2 (in bits per unit time). This work constitutes a generalization of deltacoupling UDW model to arbitrary (globally hyperbolic) curved spacetimes, as we presented the calculations via algebraic approach in QFT instead of the more conventional calculation in flat spacetime [15,19,[22][23][24][25]). Furthermore, as we do not need to pick a specific CCR representation until the very end, this calculation is much simpler to work with when one wishes to consider different field states.…”

“…The UDW model also allows for local measurement theory [6] and simplified generalizations that can capture effects from non-standard metrics and higher-curvature gravity [7]. The UDW model and its covariant generalizations have been used to in various contexts in the field of relativistic quantum information (RQI) (see, e.g., [8][9][10][11][12][13][14][15][16][17][18][19], and references therein).…”

Characterization of non-perturbative qubit channel induced by a quantum field

“…For two-qubit systems, in particular, where two-party communication is most naturally set in, there has been quite a few known results in the non-perturbative regimes in flat spacetimes (see, e.g., the thorough work in [10,11,27]), though this has changed recently to include curved backgrounds exploiting the sort of generalities we consider here [13-15, 29, 62]. The three-qubit system calculation has been only confined to entanglement and mutual information harvesting in flat space [26,97,98], and there is also an example on sabotaging of correlations where they consider arbitrary number of detectors were considered in flat space) [25]. It is actually not difficult to show that there are ways to organize these calculations in the same spirit as this work in curved spacetimes.…”

“…where f (x) = λχ(τ )F (x), χ and F are switching and spatial profiles in the detector's rest frame, χ and F are their respective Fourier transforms, and λ is the coupling constant. For pointlike gapless detector centred at the origin with Gaussian switching, we have F (x) = δ 3 (x) and χ(τ ) = e −τ 2 /T 2 , where T is the switching width 25 . We can then plot the Rényi entropy S 2 (ω ) as a function of temperature β −1 , as shown in Figure 3.…”

“…Furthermore, since the UDW model is easily generalized to include multiple detectors, it is straightforward to apply it to study relativistic quantum communication (RQC) between two localized parties in curved spacetimes [8][9][10][11][12][13][14][15]. There are numerous other applications of the UDW model in other contexts (see, e.g., [16][17][18][19][20][21][22][23][24][25][26] and references therein).…”