Experimental confirmation of Landauer's principle

Landauer's principle, formulated in 1961, postulates that irreversible logical or computational operation such as memory erasure must dissipate heat, no matter how slowly they are performed. For example, to ``reset to one'' a memory that can be in state 0 or 1 requires at least kT ln2 of work, 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 the first confirmation 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 a force = -grad U(x,t) via 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.