Wei Cui: Randomly distilling W-class states into general configurations of two-party entanglement

Abstract:

In this talk we will discuss about the task of converting a single N-qubit W-class state (of the form sqrt(x_0)|00...0> + sqrt(x1)|10...0>+· · ·+ sqrt(x_N)|00...1>) into maximum entanglement shared between two random parties. Previous studies in random distillation have not considered how the particular choice of target pairs affects the transformation, and here we develop a strategy for distilling into general configurations of target pairs. We completely solve the problem of determining the optimal distillation probability for all three-qubit configurations and most four-qubit configurations when x0 = 0. Our proof involves deriving new entanglement monotones defined on the set of four-qubit W-class states. As an additional application of our results, we present new upper bounds for converting a generic W-class state into the standard W state |W_N>=sqrt(1/N)(|10...0> + ··· + |00...1>).