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UID:UW-Physics-Event-1163
DTSTART:20080409T160000Z
DURATION:PT1H0M0S
DTSTAMP:20260506T215448Z
LAST-MODIFIED:20080404T151835Z
LOCATION:5310 Chamberlin
SUMMARY:Reconstructing the Wigner function of a photonic Schrodinger c
 at in a cavity: a movie of decoherence\, Atomic Physics Seminar\, Serg
 e Haroche\, Laboratoire Kastler Brossel
DESCRIPTION:The development of super-high finesse cavities made of pai
 rs of mirrors which bounce microwave photons back and forth for times 
 up to a few tenths of a second has opened a new domain in quantum opti
 cs. It is now possible to &quot\;look&quot\; at stored light without d
 estroying it\, to prepare by quantum non-demolition (QND) measurements
  well-defined photons number states and to observe the quantum jumps b
 etween them(1). One can also generate and study mesoscopic non-classic
 al states containing several photons\, which survive long enough to be
  measured and fully characterized. We will describe how a single atom 
 passing between mirrors trapping a coherent field prepares a superposi
 tion of photonic states with opposite phases.  This state is called a 
 &quot\;Schroedinger cat&quot\;  by reference to the feline that the fo
 unding father of quantum physics imagined to be suspended in a superpo
 sition of life and death. This highly non-classical state is represent
 ed in phase space by a quasi-probability distribution\, called Wigner 
 function\, which exhibits Gaussian peaks corresponding to its classica
 l components (the &quot\;dead&quot\; and &quot\;alive&quot\;  parts of
  the cat) along with  interference fringes describing its quantum cohe
 rence. By performing QND measurements of the photon number parity\, we
  have reconstructed these Wigner function and recorded the progressive
  disappearance of their interference features. Movies of the decoheren
 ce process are realized in this way\, which directly illustrate how a 
 mesoscopic system evolves from quantum to classical.
URL:https://www.physics.wisc.edu/events/?id=1163
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