Technical Program

Paper Detail

Paper Title Entropy Bound for the Classical Capacity of a Quantum Channel Assisted by Classical Feedback
Paper IdentifierMO2.R5.1
Authors Dawei Ding, Yihui Quek, Stanford University, United States; Peter Shor, Massachusetts Institute of Technology, United States; Mark M. Wilde, Louisiana State University, United States
Session Quantum Channel Capacity and Codes
Location Saint Victor, Level 3
Session Time Monday, 08 July, 11:40 - 13:00
Presentation Time Monday, 08 July, 11:40 - 12:00
Manuscript  Click here to download the manuscript
Abstract We prove that the classical capacity of an arbitrary quantum channel assisted by a free classical feedback channel is bounded from above by the maximum average output entropy of the quantum channel. As a consequence of this bound, we conclude that a classical feedback channel does not improve the classical capacity of a quantum erasure channel, and by taking into account energy constraints, we conclude the same for a pure-loss bosonic channel. The method for establishing the aforementioned entropy bound involves identifying an information measure having two key properties: 1) it does not increase under a one-way local operations and classical communication channel from the receiver to the sender and 2) a quantum channel from sender to receiver cannot increase the information measure by more than the maximum output entropy of the channel. This information measure can be understood as the sum of two terms, with one corresponding to classical correlation and the other to entanglement.