The dynamics of excitons in a one-dimensional ensemble with partial spatial order are studied. During optical excitation, cold Rydberg atoms spontaneously organize into regular spatial arrangements due to their mutual interactions. This emergent latt
ice is used as the starting point to study resonant energy transfer triggered by driving a $nS$ to $n^prime P$ transition using a microwave field. The dynamics are probed by detecting the survival probability of atoms in the $nS$ Rydberg state. Experimental data qualitatively agree with our theoretical predictions including the mapping onto XXZ spin model in the strong-driving limit. Our results suggest that emergent Rydberg lattices provide an ideal platform to study coherent energy transfer in structured media without the need for externally imposed potentials.
It is shown that an existing method to study ideal individual attacks on the BB84 QKD protocol using error discard can be adapted to reconciliation with error correction, and that an optimal attack can be explicitly found. Moreover, this attack fills
Luetkenhaus bound, independently of whether error positions are leaked to Eve, proving that it is tight. In addition, we clarify why the existence of such optimal attacks is not in contradiction with the established ``old-style theory of BB84 individual attacks, as incorrectly suggested recently in a news feature.
