Symmetric extendibility for a class of qudit states

摘要: The concept of symmetric extendibility has recently drawn attention in the context tolerable error rates quantum cryptography, where it can be used to decide whether states shared between two parties purified by means entanglement purification with one-way classical communication only. Unfortunately, at present there exists no simple general criterion a state possesses extension or not. In this paper, we derive criteria for within subclasses all two-qudit states. Using these criteria, completely solve problem two-parameter family states, which includes isotropic as subclass.