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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-2529
DTSTART:20120127T160000Z
DURATION:PT1H0M0S
DTSTAMP:20260420T062257Z
LAST-MODIFIED:20120109T164047Z
LOCATION:5310 Chamberlin
SUMMARY:Preparation and stabilisation of a non-classical field in cavi
 ty by quantum feedback\, Atomic Physics Seminar\, Clément Sayrin\, La
 boratoire Kastler Brossel\, l'Ecole Normale Supérieure
DESCRIPTION:Feedback loops are central in most classical control proce
 dures. A controller compares the signal measured by a sensor with the 
 target value. It then adjusts an actuator to bring the signal close to
  the target value. Generalizing this scheme to the quantum world must 
 overcome a fundamental difficulty: the sensor measurement causes a ran
 dom back-action on the system. I will present how we have been able to
  continuously operate a quantum feedback loop stabilizing photon numbe
 r states in a very high finesse Fabry-Perot cavity. Circular Rydberg a
 toms repeatedly achieve weak quantum non-demolition measurements of th
 e photon number. A classical computer estimates in real-time the densi
 ty matrix of the field\, based on the outcome of these measurements\, 
 and taking into account all known experimental imperfections. It then 
 calculates the amplitude of small classical microwave fields injected 
 into the cavity to bring the field into the target state. We have been
  able to prepare on demand and stabilize Fock states containing from 1
  to 4 photons. This achievement opens interesting perspectives for the
  production and control of non-classical states for quantum informatio
 n processing.
URL:https://www.physics.wisc.edu/events/?id=2529
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