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arXiv 1708.03030cond-mat.stat-mechcs.ITmath.ITnlin.CD
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Landauer界限之上与之外:模块化的热力学

Above and Beyond the Landauer Bound: Thermodynamics of Modularity

Alexander B. Boyd, Dibyendu Mandal, James P. Crutchfield

摘要:

信息处理通常通过模块化单元的组合发生,例如通用逻辑门。与全局集成信息处理相比,模块化信息处理的好处在于,复杂的全局计算可以通过一系列简单的、局部化的信息处理操作更容易和灵活地实现,这些操作仅控制和改变局部自由度。我们表明,尽管有这些好处,有不可避免的热力学成本模块化-成本,直接从本地化处理的操作,并超越兰道的耗散界限擦除信息。然而,当它们全局协调控制信息库的所有自由度时,集成计算可以达到朗道界。不幸的是,模块化实现很容易丢失信息承载自由度之间的全局相关性。这是昂贵的,因为这种相关性是热力学燃料。我们量化模块化计算的最小不可挽回的耗散在全球非平衡自由能的变化之间的差异,它捕获这些全球的相关性,和本地(边际)的非平衡自由能的变化,这限制了模块化的工作生产。这种模块化耗散与模块化地执行计算任务所需的额外工作量成比例。它对物理嵌入式传感器有直接的影响,称为信息棘轮。我们展示了如何通过设计内部棘轮状态来规避模块化耗散,这些棘轮状态捕获棘轮信息库中的全局相关性和模式。通过这种方式设计,信息棘轮与全球集成计算的最佳热力学效率相匹配。

英文摘要:

Information processing typically occurs via the composition of modular units, such as universal logic gates. The benefit of modular information processing, in contrast to globally integrated information processing, is that complex global computations are more easily and flexibly implemented via a series of simpler, localized information processing operations which only control and change local degrees of freedom. We show that, despite these benefits, there are unavoidable thermodynamic costs to modularity---costs that arise directly from the operation of localized processing and that go beyond Landauer's dissipation bound for erasing information. Integrated computations can achieve Landauer's bound, however, when they globally coordinate the control of all of an information reservoir's degrees of freedom. Unfortunately, global correlations among the information-bearing degrees of freedom are easily lost by modular implementations. This is costly since such correlations are a thermodynamic fuel. We quantify the minimum irretrievable dissipation of modular computations in terms of the difference between the change in global nonequilibrium free energy, which captures these global correlations, and the local (marginal) change in nonequilibrium free energy, which bounds modular work production. This modularity dissipation is proportional to the amount of additional work required to perform the computational task modularly. It has immediate consequences for physically embedded transducers, known as information ratchets. We show how to circumvent modularity dissipation by designing internal ratchet states that capture the global correlations and patterns in the ratchet's information reservoir. Designed in this way, information ratchets match the optimum thermodynamic efficiency of globally integrated computations.

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