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VERSION:2.0
PRODID:Icfo
X-PUBLISHED-TTL:P1W
BEGIN:VEVENT
UID:6a47317a87085
DTSTART:20260710T100000Z
SEQUENCE:0
TRANSP:OPAQUE
DTEND:20260710T110000Z
LOCATION:Seminar Room
SUMMARY:ICFO | MOHAMMAD MEHBOUDI
CLASS:PUBLIC
DESCRIPTION:Famously\, the quantum Fisher information&ndash\;&ndash\;the ma
 ximum Fisher information over all physical measurements&ndash\;&ndash\;is 
 additive for independent copies of a system and the optimal measurement ac
 ts locally. We are left to wonder: does the same hold when the set of acce
 ssible measurements is constrained? Such constraints are necessary to acco
 unt for realistic experimental restrictions. Here\, we consider a fully Ga
 ussian scenario focusing on only Gaussian measurements. We prove that the 
 optimal Gaussian measurement protocol remains local\, if the information i
 s encoded in either the displacement or the covariance matrix. However\, w
 hen the information is imprinted on both\, this no longer holds true: we p
 rovide with a necessary and sufficient condition for super additivity of t
 he Gaussian Fisher information\, and when the condition is met we construc
 t a simple global Gaussian measurement where the Fisher information become
 s super additive. These results can improve parameter estimation tasks via
  feasible tools. Namely\, in quantum optical platforms our proposed global
  operation requires only passive global operations and single mode Gaussia
 n measurements. We demonstrate this in two examples where we estimate sque
 ezing and losses. While in the former case there is a significant gap betw
 een the Fisher information of the optimal Gaussian measurement and the qua
 ntum Fisher information for a single copy\, this gap can be reduced with j
 oint Gaussian measurements and closed in the asymptotic limit of many copi
 es.
DTSTAMP:20260703T035018Z
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