One-shot reverse Shannon theorem for Multiple Access Channel and the decoupling theorem in quantum information theory

Title of the Talk:One-shot reverse Shannon theorem for Multiple Access Channel and the decoupling theorem in quantum information theory
Host Faculty: Dr.Rakesh Venkat
Speaker: Dr. Aditya Nema
Date: 30th April 2026
Time: 11.:00 am
Venue: CSE Seminar hall, Ground floor, CSE-EECS-LH1 (Ground floor, CSE Department)

Abstract
We will start with a high level sketch of the research in the area of quantum information processing with emphasis on some Shannon theoretic tools used in certain fundamental tasks. We will explore two analytical tools in this talk - reverse Shannon theorem and the decoupling theorem. In the first half of the talk we will see the so-called reverse Shannon theorem which provides a quantitative bound for the simulation of a single instance of a given Multiple Access Channel (MAC) using shared randomness and classical communication. The goal is to derive a one-shot cost region for simulating (within the above framework) a MAC. The achievability is quite simple yet widely applicable and the non-trivial part is to show an almost matching converse. This task is very closely related to the task of message compression or the source coding. There are several interesting open directions in this area and I will briefly mention them. The second half of the talk will be purely quantum, focussing on the technique called decoupling in quantum information theory. Here the task is to determine when a given bipartite quantum state can be converted to a state that is close to a tensor product state. The nice result is that such a transformation is governed by the entropic quantities. This is used ubiquitously in Shannon theoretic tasks. We will see a tightest and a computationally efficient measure concentration result for this tool.

Bio
Dr. Aditya Nema is currently an Assistant Professor in the department of Electrical Engineering. Prior to this, he had a brief appointment as an Assistant Professor, jointly in the department of Electrical Engineering and Mathematics at IIT Gandhinagar. Even before that he has worked as a postdoc in the Institute of Quantum Information at RWTH Aachen University, Germany and a Research Assistant Professor in the Graduate School of Informatics at Nagoya University. He obtained his Masters and PhD from STCS TIFR Mumbai in quantum information theory and a Bachelor’s in Electronics and Telecommunication Engineering. His primary research interests are in classical and quantum information theory, quantum computation, quantum error correction and quantum machine learning. He likes to work broadly in the areas involving the use of probability theory and functional analysis.