Tomographic entanglement indicators in frequency combs and Talbot carpets

Abstract

Recent theoretical investigations on tomographic entanglement indicators have showcased the advantages of the tomographic approach in the context of continuous-variable (CV), spin and hybrid quantum systems. Direct estimation of entanglement using experimental data from the IBM quantum computing platform and NMR experiments has also been carried out in earlier work. A similar investigation in the context of CV systems is necessary to assess fully the utility of the tomographic approach. In this paper, we highlight the advantages of this approach in the context of experiments reported in the literature on two CV systems, namely, entangled Talbot carpets and entangled biphoton frequency combs. We use the tomographic entanglement indicator to estimate the degree of entanglement between a pair of Talbot carpets, and demonstrate that this provides a simpler and more direct procedure as compared to the one suggested in the experiment. We also establish that the tomograms corresponding to two biphoton frequency combs carry clear entanglement signatures that distinguish between the two states.

A tomographic approach to the sum uncertainty relation and quantum entanglement in continuous variable systems

“…It is therefore advantageous to avoid detailed state reconstruction wherever possible, and to extract reliable entanglement indicators solely from tomograms. Such entanglement indicators have been proposed in the literature and their efficacy examined in CV and HQ systems by comparing them with standard entanglement measures and monotones (Sharmila et al, 2020;Sharmila et al, 2022).…”

“…is the bipartite tomographic entropy (Sharmila et al, 2020;Sharmila et al, 2022). Note the similarity in form of Eq.…”