Robust self-testing of unknown quantum systems into any entangled two-qubit states

Self-testing is a device-independent approach to estimate the state and measurement operators without the need to assume the dimension of our quantum system. In this paper, we show that one can self-test black boxes into any pure entangled two-qubit state by performing simple Bell-type experiments. The approach makes use of only one family of Bell inequalities with two inputs and two outputs. Furthermore, we outline the sufficient conditions for one to self-test any dimensional bipartite entangled state. All these methods are robust to small but inevitable experimental errors.