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

计算和存储海量数据能力的指数级增长正在推动人类状况的革命性变化。它导致了一个高度互联的世界，世界上遥远的地方都可以获得信息。目前对基础设施系统互连的关注，如电网、金融市场、医疗保健系统和物联网（IoT），都与集成芯片的进步有直接关系，按照摩尔定律，集成芯片的复杂性和组件数量几乎每两年翻一番。鲜为人知的事实是，每次计算的能量耗散已经超过了移动计算革命核心的摩尔定律，使具有高计算能力的小型设备成为可能，包括轻型笔记本电脑、平板电脑和手机。随着这种指数级的增长，不可避免地会达到当前计算和内存相关技术的方法和实践的极限。这一建议解决了计算和存储器的基本操作，并考虑了执行这些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操作相关的能源成本。它提供了概念验证实验和方法来证明计算和存储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。对计算操作基本原语的相关分析和概念验证实验将指导未来节能计算平台的实现，并将继续显著提高计算的速度和效率。该项目的重点是计算和内存能量学的基本限制。该项目以分析和实验两种方式研究计算操作的原语。它通过热浴中双阱势中粒子的位置来抽象记忆位的状态。在潜在景观中，粒子在井间的转移用于实现AND、NOT和擦除操作。在项目目标下，将解析推导出双阱势中粒子态转移的最小能量界。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，并将熵的变化与状态转移相关的能量联系起来。状态的转移可以在双阱势中测量粒子的状态或不测量粒子的状态时完成；在这里，反馈的影响，其中测量指导协议转移状态将被理解和分析。理论基础，连接计算，统计力学，和反馈将伴随着一个多功能的实验平台。通过控制具有适合研究的能量学尺度的光场，可以实现双阱势。实验协议将适应不同状态转移速度的需要；模拟准静态过程很重要。对粒子位置的精确测量将用于估计粒子穿过井所需的能量。测量协议将被精确地表征，这将使研究基于测量改变传输协议的闭环策略成为可能。该项目将提供基本计算原语的分析和概念验证实验实现，其能量足迹将减少几个数量级。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.