Figure 1: The scheme of self-testing.
From: All pure bipartite entangled states can be self-tested
(a) First, measurement inputs and outputs from a Bell experiment in a laboratory are recorded. (b) Using the recorded experimental data, one can estimate the correlations of the Bell experiment. (c) A local isometry Φ is constructed mathematically, as in the circuit diagram. Gates F and 
in this diagram denote the quantum Fourier transform and inverse quantum Fourier transform respectively. Gates R and S, which act jointly on 
and the ancillary system, are controlled unitaries defined precisely in the Supplementary Methods. (d) If one can show, using the correlations, that the local isometry is such that 
, then we conclude that the correlations self-test 
.
