Coherence is understood as a fundamental concept in optics and in quantum physics. However, it has the peculiarity of not being a phenomenon in itself and it only manifests through other phenomena. Although this seemed to be well understood long ago, the new physics proposes scenarios which challenge the interpretation of this concept.
We consider the distribution of entangled resources for various quantum information protocols and user scenarios via quantum networks. We introduce private and quantum capacities for the entire network and provide upper and lower bounds that, given the single channel capacities or bounds on them, can be efficiently computed using linear programs (LPs).
Photonic states with large and fixed photon numbers, such as Fock states, enable quantum-enhanced metrology but remain an experimentally elusive resource. A potentially simple, deterministic and scalable way to generate these states consists of fully exciting N quantum emitters equally coupled to a common photonic reservoir, which leads to a collective decay known as Dicke superradiance.
We investigate monogamy of correlations in the Bloch representation. Here, monogamy of correlations can be understood as direct relations between different correlation tensor elements.
To that end we introduce the split Bloch basis, that is particularly useful for representing quantum states with low dimensional support and thus amenable to purification arguments.