Minimal qubit tomography
  We present, and analyze thoroughly, a highly symmetric and efficient scheme for the determination of a single-qubit state, such as the polarization properties of photons emitted by a single-photon source. In our scheme there are only four measured probabilities, just enough for the determination of the three parameters that specify the qubit state, whereas the standard procedure would measure six probabilities. 
Jaroslav \v{R}eh\'a\v{c}ek, Berthold-Georg Englert, Dagomir   Kaszlikowski