We study the decoherence properties of entangled pairs of qubits theoretically and experimentally. We find that the entanglement dynamics of maximally-entangled qubit pairs, when transmitted through unital Pauli channels, is simply manifested by the parameters of the Bloch/Poincaré sphere representation of the noise.

The obtained relations were verified experimentally using an all-optical setup. Entangled pairs of photons where generated collinearly by spontaneous parametric down-conversion, where the information was encoded in their polarization degree of freedom. The photons were sent through controllable unital channels which are composed of birefringent crystals and wave-plates [1,2]. The Post-selected entanglement of the output states was measured using a quantum state tomography procedure, and compared successfully to the theoretical predictions.

[1] A. Shaham and H. S. Eisenberg, Phys. Rev. A 83, 022303 (2011).

[2] Assaf Shaham and Hagai S. Eisenberg, Opt. Lett. 37, 2643 (2012).