Fundamental limitations on communication over phase-insensitive Gaussian channels - Kunal Sharma

One of the main goals of quantum information theory is to find the optimal rates of communicating classical or quantum information when allowing for quantum effects. In particular, the characterization of the quantum and private capacities of a thermal channel is of principal interest, as thermal channels model free-space communication with background thermal radiation affecting the input state, in addition to transmission loss. In our work, we establish upper bounds on the energy-constrained quantum and private capacities of the thermal channel. In this seminar talk, I will discuss three different techniques to establish our upper bounds on the energy-constrained quantum capacity of a thermal channel, and additionally, I will compare these bounds for different parameter regimes of background thermal radiation and transmission loss. I will also discuss a strategy that leads to an improved lower bound on the energy-constrained private capacity of a thermal channel.
Joint work with Mark M. Wilde (LSU), Sushovit Adhikari (LSU), and Masahiro Takeoka (NICT), and available at