Secret key capacity of the thermal-loss channel: improving the lower bound
Carlo Ottaviani, Riccardo Laurenza, Thomas Cope, Gaetana Spedalieri, Samuel L. Braunstein, Stefano Pirandola · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2016
We consider the secret key capacity of the thermal loss channel, which is modeled by a beam splitter mixing an input signal mode with an environmental thermal mode. This capacity is the maximum value of secret bits that two remote parties can generate by means of the most general adaptive protocols assisted by unlimited and two-way classical communication. To date, only upper and lower bounds are known. The present work improves the lower bound by resorting to Gaussian protocols based on suitable trusted-noise detectors.