We propose a scheme for preparing arbitrary two-photons polarization-entangled mixed states via controlled location decoherence. The scheme uses only linear optical devices and single-mode optical fibers, and may be feasible in experiment within current optical technology.
We propose a scheme for preparing an arbitrary polarization-entangled mixed state starting from a pure state with location decoherence owing to the path difference. The scheme, using linear optical devices (beam splitter, half wave plate, quarter wave plate) and single-mode optical fibers, is feasible in experiment within current optical technology. We also give a simplified scheme for a special case rho=p∣psi><psi∣+(1−p)∣phi><phi∣.
Two methods for creating arbitrary two-photon polarization pure states are introduced. Based on these, four schemes for creating two-photon polarization mixed states are proposed and analyzed. The first two schemes can synthesize completely arbitrary two-qubit mixed states, i.e., control all 15 free parameters: scheme I requires several sets of crystals, while scheme II requires only a single set, but relies on decohering the pump beam. Additionally, we describe two further schemes which are much easier to implement. Although the total capability of these is still being studied, we show that they can synthesize all two-qubit Werner states, maximally entangled mixed states, Collins-Gisin states, and arbitrary Bell-diagonal states.