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Physics Department Colloquium
Testing Landauer’s Principle in a feedback trap
Date: Friday, December 7th
Time: 3:30 pm
Place: 2241 Chamberlin Hall (coffee at 4:30 pm)
Speaker: John Bechhoefer, Simon Fraser University
Abstract: 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.

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.
Host: Coppersmith
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