Cost of quantum secret key
Karol Horodecki, Leonard Sikorski, Siddhartha Das, and Mark M. Wilde
Quantum 10, 2098 (2026). https://doi.org/10.22331/q-2026-05-06-2098 In this paper, we develop the resource theory of quantum secret key. Operating under the assumption that entangled states with zero distillable key do not exist, we define the key cost of a quantum state, and device. We study its properties through the lens of a quantity that we call the key of formation. The main result of our paper is that the regularized key of formation is an upper bound on the key cost of a quantum state. T