Resource-theoretic efficacy of the single copy of a two-qubit entangled state in a sequential network

Abstract

How best one can recycle a given quantum resource, mitigating the various difficulties involved in its preparation and preservation, is of considerable importance for ensuring efficient applications in quantum technology. Here, we demonstrate quantitatively the resource-theoretic advantage of reusing a single copy of a two-qubit entangled state toward information processing. To this end, we consider a scenario of sequential entanglement detection of a given two-qubit state by multiple independent observers on each of the two spatially separated wings. In particular, we consider equal numbers of sequential observers on the two wings. We first determine the upper bound on the number of observers who can detect entanglement employing suitable entanglement witness operators. In terms of the parameters characterizing the entanglement consumed and the robustness of measurements, we then compare the above scenario with the corresponding scenario involving multiple pairs of entangled qubits shared among the two wings. This reveals a clear resource-theoretic advantage of recycling a single copy of a two-qubit entangled state in the sequential network.