Quantum Queue-Channels as building blocks for Quantum Communication Networks
Motivated by the growing interest in designing and building quantum communication networks, we study the fundamental limits of classical communications over quantum networks. The inevitable buffering of quantum bits at intermediate nodes and quantum repeaters causes them to suffer a waiting time-dependent decoherence — the longer a qubit waits in a buffer, the more it decoheres, leading to an error/erasure. We model the sequential processing of qubits using a single server queue, and derive expressions for the classical capacity of such a quantum ‘queue channel’, focusing mainly on the case of erasures. More generally, whenever the underlying quantum noise model is additive, we obtain a single-letter upper bound on the classical capacity of the corresponding quantum queue-channel. Next, we study a quantum Jackson network, which is a network of Markovian queue-channels. Focusing on erasures, we characterize the classical capacity of a quantum Jackson network with waiting time-dependent erasures. Collaborative work with Avhishek Chatterjee, Prabha Mandayam, Jaswanthi Mandalapu.
Krishna Jagannathan obtained his B. Tech. in Electrical Engineering from IIT Madras in 2004, and the S.M. and Ph.D. degrees in Electrical Engineering and Computer Science from the Massachusetts Institute of Technology (MIT) in 2006 and 2010 respectively. During 2010-2011, he was a visiting post-doctoral scholar in Computing and Mathematical Sciences at Caltech, and an off-campus post-doctoral fellow at MIT. Since November 2011, he has been with the Department of Electrical Engineering, IIT Madras, where he is currently an associate professor. His research interests lie in the stochastic modeling and analysis of communication networks, network control, and queuing theory.