Dartmouth Events

Physics & Astronomy Quantum/Nano Seminar - Prof. Mary Beth Ruskai, UMASS-Lowell

Title: "Local Additivity Revisited with Implications for Demonstrating Superadditivity"

Tuesday, November 16, 2021
4:00pm – 5:00pm
In-person: Wilder 102 / Via Zoom (email for link & password)
Intended Audience(s): Public
Categories: Lectures & Seminars
Abstract:  It is by now well known that both the minimal output entropy of a quantum 
channel and its capacity for transmitting quantum information are non-additive. 
However, explicit examples remain elusive.
 
 Gour and Friedland showed that the minimal output entropy of a quantum channel
 is locally additive.  This result can be extended to the
maximal output relative entropy  H(P,Q) = Tr P ( log P - log Q )   
when the second argument Q  is fixed.  This can be used to obtain a necessary
and sufficient condition for superadditivity of the classical capacity of a quantum
channel which does not require finding either the capacity or the optimal input 
average of the product channel.
 
I'll sketch the proof of local additivity and discuss the implications for a
numerical search for superadditivity.
For more information, contact:
Tressena Manning
603-646-2854

Events are free and open to the public unless otherwise noted.