Fast Measurements of Entangled Photons

We report on a system for the generation and measurement of polarization entangled photons. High speed quantum state tomographies with a raw fidelity of >; 91 % with respect to an ideal entangled state are recorded in <; 2 seconds, with longer-term accidental-count subtracted fidelities exceeding 99%. Two-photon interference measurements are recorded using an automated alignment and measurement procedure with the signal distributed over 20 km of fiber. These high speed measurement methods are useful for high rate monitoring of entangled states.