Thermodynamics of Information Processing in Small Systems
Thermodynamics of Information Processing in Small Systems
复制标题
小型系统信息处理的热力学
DOI：
10.1143/ptp.127.1
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发表时间：
2012
影响因子：
--
通讯作者：
Takahiro Sagawa
中科院分区：
文献类型：
--
作者：
T. Sagawa;M. Ueda;Takahiro Sagawa and Masahito Ueda;Takahiro Sagawa
我们回顾了信息处理热力学的一般理论。本课题的背景是最近发展的非平衡统计力学和量子（和经典）信息论。这些理论与操纵和观察小系统的现代技术密切相关；例如，经典体系中的大分子和胶体粒子，量子体系中的量子光学系统和量子点。首先，我们回顾了热力学第二定律在小型热力学系统受量子反馈控制的情况下的推广。广义第二定律是用一个不等式来表示的，这个不等式包括测量得到的信息项，以及热力学量，如自由能。这种不平等导致了可以由“麦克斯韦妖”提取的功的基本上限，它可以被视为一个具有存储测量结果的存储器的反馈控制器。其次，我们回顾了热力学第二定律对量子系统记忆的测量和信息擦除过程的概括。广义第二定律由不等式组成，这些不等式确定了测量和信息消除所需的能量成本的下界。擦除的不平等导致了一个特殊情况下著名的兰道尔原理。此外，这些不等式使我们能够调和麦克斯韦妖与热力学第二定律。在这些不等式中，热力学量和信息内容被同等对待。事实上，这些不等式是与模型无关的，因此它们可以应用于广泛的信息处理。因此，这些不等式可以称为“信息热力学”第二定律。
We review a general theory of thermodynamics of information processing. The background of this topic is the recently-developed nonequilibrium statistical mechanics and quantum (and classical) information theory. These theories are closely related to the modern technologies to manipulate and observe small systems; for example, macromolecules and colloidal particles in the classical regime, and quantum-optical systems and quantum dots in the quantum regime.First, we review a generalization of the second law of thermodynamics to the situations in which small thermodynamic systems are subject to quantum feedback control. The generalized second law is expressed in terms of an inequality that includes the term of information obtained by the measurement, as well as the thermodynamic quantities such as the free energy. This inequality leads to the fundamental upper bound of the work that can be extracted by a “Maxwell's demon”, which can be regarded as a feedback controller with a memory that stores measurement outcomes.Second, we review generalizations of the second law of thermodynamics to the measurement and information erasure processes of the memory of the demon that is a quantum system. The generalized second laws consist of inequalities that identify the lower bounds of the energy costs that are needed for the measurement and the information erasure. The inequality for the erasure leads to the celebrated Landauer's principle for a special case. Moreover, these inequalities enable us to reconcile Maxwell's demon with the second law of thermodynamics.In these inequalities, thermodynamic quantities and information contents are treated on an equal footing. In fact, the inequalities are model-independent, so that they can be applied to a broad class of information processing. Therefore, these inequalities can be called the second law of “information thermodynamics”.