Hoang Thai M, Pan Rui, Ahn Jonghoon, Bang Jaehoon, Quan H T, Li Tongcang
Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA.
School of Physics, Peking University, Beijing 100871, People's Republic of China.
Phys Rev Lett. 2018 Feb 23;120(8):080602. doi: 10.1103/PhysRevLett.120.080602.
Nonequilibrium processes of small systems such as molecular machines are ubiquitous in biology, chemistry, and physics but are often challenging to comprehend. In the past two decades, several exact thermodynamic relations of nonequilibrium processes, collectively known as fluctuation theorems, have been discovered and provided critical insights. These fluctuation theorems are generalizations of the second law and can be unified by a differential fluctuation theorem. Here we perform the first experimental test of the differential fluctuation theorem using an optically levitated nanosphere in both underdamped and overdamped regimes and in both spatial and velocity spaces. We also test several theorems that can be obtained from it directly, including a generalized Jarzynski equality that is valid for arbitrary initial states, and the Hummer-Szabo relation. Our study experimentally verifies these fundamental theorems and initiates the experimental study of stochastic energetics with the instantaneous velocity measurement.
诸如分子机器等小系统的非平衡过程在生物学、化学和物理学中普遍存在，但往往难以理解。在过去二十年中，已经发现了几个非平衡过程的精确热力学关系，统称为涨落定理，并提供了关键见解。这些涨落定理是第二定律的推广，可以通过一个微分涨落定理统一起来。在这里，我们使用光学悬浮纳米球在欠阻尼和过阻尼 regimes 以及空间和速度空间中对微分涨落定理进行了首次实验测试。我们还测试了几个可以直接从它得到的定理，包括对任意初始状态都有效的广义 Jarzynski 等式和 Hummer-Szabo 关系。我们的研究通过实验验证了这些基本定理，并通过瞬时速度测量开启了随机能量学的实验研究。
