Researcher, Physics of Information Group, IBM TJ Watson Research Center
Graeme Smith is a Research Staff Member in the Physics of Information group at IBM's TJ Watson Research
Center, focusing on problems in noisy communication and computation. He was previously a postdoc at IBM
and the University of Bristol. Graeme got his Ph.D. in physics at Caltech as a member of the Institute for
Quantum Information, and was an undergraduate at the University of Toronto.
While quantum information theory is typically studied in the finite-dimensional regime, many real-world physical channels are best described in terms of continuous variables. The simplest such channels are gaussian bosonic channels, which result from a quadratic unitary interaction
between bosonic transmission modes and an inaccessible environment in the vacuum state. This class includes good approximations of most realistic optical channels. I'll review the theory of quantum information for continuous variables, then show that the set of bosonic gaussian channels is sufficently rich to allow superactivation: there are pairs of channels, neither of which can transmit quantum information on its own, that can nevertheless be used together for reliable quantum communication. I'll
discuss the potential for exhibiting this effect in the lab or, better yet, finding it "in the wild".