Biophysics and Soft Matter Seminar

Landauer’s principle and irreversibility

Wed, 27 Jan 2016
Biophysics and Soft Matter Seminar
Momcilo Gavrilov
SFU Physics
Landauer’s principle and irreversibility
Jan 27, 2016


A feedback trap is a device that can precisely trap and manipulate a single microscopic object in an arbitrary virtual potential.  It can also impose any time dependant transformation of a potential and measure thermodynamic quantities such as work and entropy.  We used a feedback trap to test the Landauer’s principle, which states that erasing a symmetric one-bit memory requires an average work of at least kTln2.  If, on the other hand, a memory is represented by a non-equilibrium state in an asymmetric double-well potential, theoretical studies predict that one can measure work below kTln2.  In our attempt to test this prediction, we found that two different erasure protocols give two different values for the asymptotic work depending on protocol symmetry in time.  To clarify this unexpected observation, we also perform related experiments that show the same observation in a simpler context, divorced from the context of Landauer's principle.  We find that although some protocols are done isothermally and arbitrarily slowly, they are still not uniformly quasistatic.

In the first part of my talk, I am going to show you measurements of work to erase symmetric and asymmetric one-bit memory.  In the second part, I will show two arbitrarily slow transformations of a system between two identical states, where one transformation does require work, while the other does not.