[QIP-Sem] MIT Quantum Information Processing Seminar Announcement

[QIP-Sem Mailing List]

Next week's MIT QIP seminar will take place on Monday, Oct. 4 at 
16:00 in 4-237, and features:


Capacity of Bosonic Communications

by Jeff Shapiro (MIT Research Laboratory of Electronics)

ABSTRACT

The capacity C for transmitting classical information is investigated 
for  Bosonic channels with isotropic Gaussian noise.  For the 
pure-loss channel -- in which signal photons may be lost in 
propagation -- the exact value of C is derived.  The Holevo 
information of this channel is shown to be additive, and a 
"classical'" encoding procedure employing coherent states is shown to 
achieve capacity.  For active channel models -- in which noise 
photons are injected from an external environment or the signal is 
amplified with unavoidable quantum noise -- upper and lower bounds 
are obtained for the capacity.  These bounds are asymptotically tight 
at low and high noise levels.  Exact capacity results -- given by the 
lower bounds -- would follow from proving the conjecture that a 
coherent-state input minimizes the output entropy from such channels.
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