Energy Efficiency in Computing Logical Operations: Fundamental Limits with and Without Feedback

计算和存储大量数据的能力呈指数级增长，正在推动人类状况的变革。它导致了一个高度连接的世界，信息可以在世界的偏远地区获得。目前对电网、金融市场、医疗保健系统和物联网（IoT）等基础设施系统互连的关注都与集成芯片的进步有直接关系，集成芯片的复杂性和组件数量几乎每两年翻一番，遵循摩尔定律。鲜为人知的是，每次计算的能量耗散已经超过了摩尔定律，摩尔定律是移动的计算革命的核心，使小型设备具有高计算能力，包括轻型笔记本电脑、平板电脑和手机。随着这种指数增长，不可避免地达到了计算和存储器相关技术的当前方法和实践的极限。该建议解决了计算和存储器的基本操作相对于执行操作所需的能量耗散的基本限制。它还研究了与执行计算和内存管理操作的测量和反馈动作相关的能量成本。它提供了概念实验和方法的证明，以证明计算和存储器相关操作的可实现性，其能量比目前的实践小几十个数量级。计算操作的基本原语的相关分析和概念实验的证明将指导未来节能计算平台的实现，并将继续显着提高计算的速度和效率。该项目的重点是对计算和内存能量的基本限制。 该项目研究分析和实验计算操作的原语。它通过粒子在热浴中的双阱势中的位置来抽象存储位的状态。利用粒子在势面中的威尔斯阱上的迁移实现与、非和擦除操作。在此目标下，解析地推导出双势阱中粒子态转移的最小能量界限。 在这里，该方法的关键方面是估计从初始状态到最终状态的熵的变化，并且将熵的变化与状态转移相关联的能量相关联。状态的转移可以在测量或不测量双阱势中粒子的状态的情况下完成;在这里，将理解和分析反馈的效果，其中测量指导用于转移状态的协议。连接计算，统计力学和反馈的理论基础将伴随着一个多功能的实验平台。双阱势将通过控制具有适合于研究的能量尺度的光场来实现。实验协议将适应不同的速度转移状态的需要，重要的是模拟准静态过程。粒子位置的准确和精确测量将用于估计移动粒子穿过威尔斯所需的能量。测量协议将被精确地表征，这将使得能够研究基于测量改变传输协议的闭环策略。该项目将提供分析和概念验证实验实现的基本计算原语的数量级更小的能源足迹。这个奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

The exponential increase in the ability to compute and store massive amount of data is fueling transformative changes in the human condition. It has led to a highly connected world with information being accessible at remote parts of the world. The current focus on interconnection of infrastructural systems such as the, power grid, financial markets, health care systems, and the Internet of Things (IoT), all bear a direct relationship to the advances in the integrated chips, where the complexity and the number of components has doubled almost every two years, following the Moore's law. Less known is the fact that the energy dissipation per computation has outpaced Moore's law which is at the heart of the mobile computation revolution, enabling, small form-factor devices packed with high computational capabilities that include, light laptops, tablets, and cell-phones. With such exponential increases, it is inevitable that limits of current approaches and practices for computation and memory related technologies are reached. This proposal addresses the basic operations of computation and memory with respect to the fundamental limits on the energy dissipation needed to perform the operations. It also studies the energy cost associated with measurement and feedback actions for performing computing and memory management operations. It provides proof of concept experiments and methods to demonstrate realizability of the computational and memory related operations with energetics tens of order smaller than the current practices. The associated analysis of fundamental primitives of computational operations and the proof of concept experiments will guide realizations of future energy efficient computational platforms and will continue the remarkable increase in speed and efficiencies with which computations are performed.The focus of the project is on the fundamental limits on the energetics of computations and memory. The project investigates primitives of computational operations both analytically and experimentally. It uses the abstraction of the state of a memory bit via the position of a particle in a double well potential in a thermal bath. Transfer of particle across the wells in a potential landscape is used to realize AND, NOT and erasure operations. Under the project goals, bounds on the minimum energetics of transferring the state of the particle in the double well potential will be analytically derived. Here, key aspect of the approach is to estimate the change in entropy from the initial to the final state, and, relating the change in entropy to the energy associated with the transfer of state. The transfer of state can be accomplished with or without measuring the state of the particle in the double well potential; here, the effect of feedback where the measurement guides the protocol for transferring the state will be understood and analyzed. The theoretical foundations that link computations, statistical mechanics, and feedback will be accompanied by a versatile experimental platform. Double-well potentials will be realized by controlling optical fields which have the scale of energetics suited for the study. The experimental protocols will accommodate the need for different speeds of transferring the state; important to emulate quasi-static processes. Accurate and precise measurements of the position of the particle will be used for the estimation of the energy required in moving the particle across wells. The measurement protocols will be precisely characterized that will enable the study of closed-loop strategies that alter the transfer protocol based on measurements. The project will provide both analytics and proof-of-concept experimental realizations of basic primitives of computations with orders in magnitude smaller energy footprint.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.