Southwest Quantum Information and Technology

Bounding the energy-constrained quantum and private capacities of phase-insensitive quantum Gaussian channels

Presenting Author: Kunal Sharma, Louisiana State University
Contributing Author(s): Mark M. Wilde, Sushovit Adhikari, and Masahiro Takeoka

One of the main aims of quantum information theory is to characterize the capacities of quantum communication channels. Bosonic Gaussian channels are some of the most important channels to consider, as they model practical communication links in which the mediators of information are photons. Of particular interest is the bosonic thermal channel, which is a more realistic model than the pure-loss channel because it incorporates environmental imperfections. In our work, we establish three different upper bounds on the energy-constrained quantum and private capacities of bosonic thermal channels. We also discuss the closeness of these upper bounds to a known lower bound for different parameter regimes of background thermal radiation and transmission loss. In particular, our results establish strong limitations on any potential superadditivity of coherent information of the thermal channel. We also find improved achievable rates of private communication through bosonic thermal channels, by employing coding schemes that make use of displaced thermal states. Although we mainly focus on thermal channels, using the techniques developed in our work we also establish bounds on the energy-constrained quantum and private capacities of other important Gaussian channels such as quantum amplifier channels and additive-noise Gaussian channels. Hence, we establish bounds on energy-constrained quantum and private capacities of all phase-insensitive quantum Gaussian channels.

Read this article online: https://arxiv.org/pdf/1708.07257.pdf

(Session 5 : Thursday from 5:00pm - 7:00 pm)