# Dresden 2006 – wissenschaftliches Programm

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# DY: Dynamik und Statistische Physik

## DY 14: Statistical Physics far from Thermal Eqilibrium

### DY 14.2: Vortrag

### Montag, 27. März 2006, 15:00–15:15, H\"UL 186

**Entropy Production of a Single Two Level System. Experimental Proof of a Fluctuation Theorem** — •Carsten Tietz^{1}, Sebastian Schuler^{1}, Thomas Speck^{2}, Udo Seifert^{2}, and Jörg Wrachtrup^{1} — ^{1}3. Physikalisches Institut, Universität Stuttgart — ^{2}II. Institut für Theoretische Physik, Universität Stuttgart

The entropy of small systems – e.g. from a single two-level-system (TLS) as used in this work – seems to be not obviously defined in Boltzmann’s definition of entropy. Nonetheless, in the last decade the concept of entropy was expanded to entropy along single trajectories. So called fluctuation theorems valid for systems driven out from equilibrium quite generally relate the probability of entropy generation to entropy annihilation.

In this work we use the fluorescence trajectories of a single defect centre in diamond to experimentally determine the entropy along a trajectory of a single TLS driven out of equilibrium. We visualise the entropy evolution along a trajectory of the pure system and the entropy production of the surrounding medium, respectively. The total entropy obey several fluctuation theorems which relate the entropy producing trajectories to the entropy annihilating ones. We proof a Jarzynski like integral fluctuation theorem as well as the more general transient fluctuation theorem.

[1] S. Schuler, T. Speck, C. Tietz, J. Wrachtrup, U. Seifert Phys. Rev. Lett. 94, 180602 (2005).