Controllable decoherence of photonic qudits

Quantum decoherence is usually an unwanted effect, and efforts are made to minimize it. This is because it acts as an information noise that encumbers the realization of many quantum information schemes and protocols. It appears that creating such noise with well defined properties is also a hard task. We will present a way in which we apply such noise in a controllable way on quantum bits (qubits) encoded in the polarization of single photons. The implementation and the characterization of principal unital quantum channels such as dephasing and isotropic channels using birefringent crystals will be discussed. 

Applying the noisy channels to photon pairs, we were able to explore the quantum-to-classical transition of initial quantum states. We will elaborate on the ability of the photon pairs to exhibit entanglement or other quantum correlations such as nonlocality and contextuality in the presence of different types and levels of noise. Specifically, we will show that the generated initial states can exhibit quantum contextuality by violating the Klyachko-Can-Binicioğlu-Shumovsky (KCBS) inequality, and that the predicted hierarchy between quantum nonlocality and KCBS contextuality (i.e., KCBS contextuality implies nonlocality) is valid for states that experienced different types of decohering unital channels.