Alastair Abbott - Communication through coherently controlled quantum channels

The coherent control of quantum systems plays a key role in quantum computation and communication, but discussion is usually limited to the coherent control of unitaries. I will consider instead the coherent control of quantum channels, and in particular two interesting possibilities: the coherent control of the order in which channels are used, and coherently controlled switching between different channels. I will focus in particular how these types of control can activate the capacity of quantum channels in new ways, where recent results have shown that, counterintuitively, it can allow information to be transmitted through completely depolarising channels. The operational meaning and relevance of these results will also be discussed.

Based on joint work with J. Wechs, D. Horsman, M. Mhalla and C. Branciard; arXiv:1810.09826