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PRODID:UW-Physics-TWaP
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UID:UW-Physics-Event-2588
DTSTART:20121207T153000
DURATION:PT1H0M0S
LOCATION:2241 Chamberlin Hall (coffee at 4:30 pm)
SUMMARY:Testing Landauer’s Principle in a feedback trap\, Physics Department Colloquium\, John Bechhoefer\, Simon Fraser University
DESCRIPTION:Landauer's principle\, formulated in 1961\, postulates that irreversible logical or computational operations such as memory erasure require work\, no matter how slowly they are performed.  For example\, to "reset to one" a one-bit memory  requires a work of at least kT ln2\, which is dissipated as heat.  In 1982\, Bennett pointed out a link to Maxwell's Demon:  Were Landauer's principle to fail\, it would be possible to repeatedly extract work from a heat bath.<br>
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We report tests of Landauer's principle in an experimental system\, where a "virtual"  double-well potential is created via a feedback loop.  We observe the position of a charged\, fluorescent\, colloidal particle in water and calculate and then apply the appropriate force using an electric field.  In a first experiment\, the probability of "erasure" (resetting to one) is unity\, and at long cycle times\, we observe that the work is compatible with kT ln2.  In a second\, the probability of erasure is zero; the system may end up in two states; and\, at long cycle times\, the measured work tends to zero.<br>

URL:http://www.physics.wisc.edu/twap/view.php?id=2588
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