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SUMMARY:Onset of Superactivation of Quantum Capacity - Marco Parentin\, Po
 litecnico di Torino
DTSTART:20250703T131500Z
DTEND:20250703T141500Z
UID:TALK233917@talks.cam.ac.uk
CONTACT:Bjarne Bergh
DESCRIPTION:The quantum capacity of a channel is a measure of its ability 
 to reliably transmit quantum information in the asymptotic memoryless sett
 ing. In 2008\, Smith and Yard demonstrated the striking phenomenon of supe
 ractivation\, where two quantum channels — each individually incapable o
 f transmitting quantum information — can exhibit a strictly positive qua
 ntum capacity when used in tandem. \nIn this talk\, we investigate this ph
 enomenon in the finite blocklength regime\, where only of a finite number 
 of channel uses\, say n\, is available. The goal is to determine the numbe
 r of channel uses required to observe this phenomenon in practice. By leve
 raging the Choi representation of quantum channels and semidefinite progra
 mming techniques\, we derive lower bounds on the n-shot quantum capacity o
 f two known zero-capacity channels and compare them with known analytical 
 bounds. These numerical results suggest that only a small number of channe
 l uses may suffice to achieve superactivation in practice.\n
LOCATION:Centre for Mathematical Sciences\, MR14
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