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UID:6a972af5897ae
DTSTART:20260908T100000Z
SEQUENCE:0
TRANSP:OPAQUE
DTEND:20260908T110000Z
LOCATION:Seminar Room
SUMMARY:ICFO | STEFAN BÄUML
CLASS:PUBLIC
DESCRIPTION:A long standing open problem in the theory of quantum resources
  is whether there exist states that need quantum key as a resource when be
 ing created using only local operations and classical communication (LOCC)
 \, but from which no quantum key is obtainable using only LOCC. Motivated 
 by the analogous term in entanglement theory such states would be called b
 ound key states. A related question is whether there exist entangled state
 s from which no cryptographic key can be distilled\, or conversely whether
  the distillable key is faithful as a measure of entanglement. We refer to
  such states mathematical bound key. In this work we shed some light on th
 ose questions\, discussing the non-triviality of defining a measure of key
  cost in analogy to the entanglement cost.\nWe provide show a surprising d
 ichotomic relationship between the existence of mathematical bound key and
  an asymptotic version of the bound key conjecture. We also generalise the
  concept of bound key to the multipartite setting of conference key agreem
 ent and discuss ways in which a key cost can be defined. We show that ther
 e exist multipartite entangled states which cannot increase the key of any
  other state when provided as an additional resource. We further provide a
  lower bound on the dimension a bound entangled state needs to have to be 
 close to a private state in trace distance\, which indicates a non-negligi
 ble memory cost of networks safe from certain attack on its nodes.
DTSTAMP:20260901T194349Z
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