Vortrag 28.10.2019

Sprecher: Felix Ritort
Universität Barcelona, Spanien

Titel: Thermodynamic Information in the Maxwell Demon

“Take a single DNA molecule and pull from its extremities while recording the force-extension curve until it gets fully straightened”. This thought experiment, which was just a dream a few decades ago, has now become standard in many research labs worldwide. Force spectroscopy techniques (such as laser optical tweezers) are a fabulous tool for manipulating and monitoring the direct action of biological molecules at the individual level, as well as measuring forces in the piconewton range and energies of roughly equivalent to 1kT, the thermal energy unit. Recent advances in such technologies, combined with theoretical developments in nonequilibrium physics, offer the exciting prospective of experimentally testing fundamental physical principles and concepts in single molecule experiments [1].

Here I will focus on one example from the thermodynamics of feedback, i.e. the experimental realization of a Maxwell demon, a Gedanken experiment proposed in 1867 by J. C. Maxwell to violate the second law of thermodynamics. I will introduce the continuous Maxwell demon, a device capable of extracting arbitrarily large amounts of work per cycle by repeated measurements of the state of a system, and experimentally test it in single DNA hairpins manipulated by an optical trap [2,3]. I will also show how to implement continuous-time feedback in DNA pulling experiments by defining a novel fluctuation theorem for multiple repeated measurements. Information-to-energy conversion with continuous-time feedback paves the way to unambiguously define the information-content of emergent high-free-energy structures in noisy environments, an essential step to uncover principles underlying evolution and life.

1. F. Ritort, The noisy and marvelous molecular world of biology, Inventions, 4 (2019) 24

2. M. Ribezzi-Crivellari and F. Ritort, Large work extraction and the Landauer limit in the Continuous Maxwell Demon, Nature Physics 15 (2019) 660
3. M Ribezzi-Crivellari and F Ritort, Work extraction, information-content and the Landauer bound in the continuous Maxwell Demon, J. Stat. Mech. (2019) 084013