Earlier studies revealed that Maxwell's demon must obey the second law of thermodynamics. However, the presence of a physical principle explaining whether using information is profitable and inevitable remains uncertain. This paper reports a novel generalization of the second law of thermodynamics, answering whether such a physical principle exists in the affirmative. The entropy production can be split into two contributions: the entropy production of the individual subsystems and the reduction in the correlations between subsystems. This novel generalization of the second law implies that if an agent exploits the latter factor, then information is indispensable and provides free energy or mechanical work outweighing the operational cost. In particular, the total entropy production has a lower bound corresponding to the positive quantity that emerges when the internal correlations of the controlled target diminish, but the correlations between the agent and target do not exist. Therefore, the information about the target is indispensable for exploiting the internal correlations to extract free energy or work. Furthermore, as the internal correlations can grow linearly with the number of the subsystems constituting the target system, control with such correlations, i.e., feedback control, can yield substantial gain that exceeds the operational cost of performing feedback control, which is negligible in the thermodynamic limit. Thus, the generalized second law presented in this paper can be interpreted as a physical principle that ensures the benefit and inevitability of information processing.

翻译：早期研究表明，麦克斯韦妖必须服从热力学第二定律。然而，是否存在一个物理解释信息利用是否有利且不可避免的物理原理仍是未知的。本文报告了热力学第二定律的一种新颖推广，对该物理原理是否存在给出了肯定回答。熵产生可分解为两个贡献：各子系统的熵产生以及子系统之间相关性的减少。这一热力学第二定律的新推广意味着，若代理利用后者这一因素，则信息不可或缺，并能提供超过运行成本的自由能或机械功。特别地，总熵产生存在一个下界，该下界对应于当被控目标的内部相关性减弱但代理与目标之间不存在相关性时出现的正量。因此，关于目标的信息对于利用内部相关性提取自由能或功是必不可少的。此外，由于内部相关性可随构成目标系统的子系统数量线性增长，利用此类相关性的控制（即反馈控制）可产生远超运行反馈控制成本的可观收益，且在热力学极限下该成本可忽略不计。因此，本文提出的广义热力学第二定律可被解释为确保信息处理的利益与不可避免性的物理原理。