FET: Small: Collaborative Research: A Probability Correlator for All-Magnetic Probabilistic Computing: Theory and Experiment

FET：小型：协作研究：全磁概率计算的概率相关器：理论与实验

• 批准号: 2006753
• 负责人: Jean Anne Incorvia
• 金额: $ 25万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-06-01 至 2024-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2006753&HistoricalAwards=false
• 关键词: FET; Small; Collaborative; Research; Probability

Probabilistic computing is a computing paradigm that can solve certain problems more efficiently than traditional digital computing. While digital computing deals with deterministic binary bits that are either 0 or 1, probabilistic computing deals with probabilistic bits (p- bits) that are sometimes 0 and sometimes 1. This is distinct from quantum computing that deals with quantum bits (q-bits) which are a superposition of 0 and 1 (and hence a mixture of both 0 and 1 all the time). Quantum computing usually requires the most hardware resources and digital computing the least, with probabilistic computing between the two. Most of the hardware resources in probabilistic computing are devoted to generating specific correlations between two or more p-bit streams. This project will study and demonstrate a system that will greatly reduce the hardware burden associated with generating correlations. The results will make probabilistic computing much more efficient than it currently is. The project will educate K-12, undergraduate, and graduate students in this field to increase the pool of skilled scientists and engineers while advancing the field of computing.One of the major challenges in probabilistic computing is the complex hardware needed to generate required correlations between probabilistic bit streams. This hardware usually consists of microcontrollers, analog-to-digital converters, shift registers, etc., that consume significant power and vastly expand the system’s footprint on a chip. In this project, an ultra-compact and extremely energy-efficient correlator or anti-correlator will be studied and demonstrated that can generate tunable degrees of anti-correlation between two p-bit streams. The approach is implemented with two magnetic tunnel junctions (MTJs) whose soft layers are in close proximity and hence dipole-coupled. Bit states are encoded in the resistance states (high or low) of the MTJs. One MTJ generates a p-bit when driven by a spin-polarized current delivering a spin-transfer-torque. The current sets the resistance state high or low with a probability determined by its magnitude, while the bit state of the other MTJ is determined by dipole coupling with the first. Very strong dipole coupling will result in perfect anti-correlation, while very weak dipole coupling will result in no correlation. The effect of dipole coupling will be controlled by applying (electrically generated) local strain to the second MTJ, which modulates its internal energy barrier, thereby modulating the degree of anti-correlation between the p-bits from 0% to 100%. This project will result in new understanding of devices that use emerging nanomagnetic physics for the next generation of computing.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.

概率计算是一种计算范式，可以比传统数字计算更有效地解决某些问题。虽然数字计算涉及0或1的确定性二进制位，但概率计算涉及有时为0，有时为1的概率位（p- lits）。这与量子计算不同的量子计算与量子位（q-bits）的量子计算不同，这些计算是0和1的叠加的量子（Q-bits）（并且是0和1的混合物）。量子计算通常需要最多的硬件资源和数字计算，而两者之间的概率计算。概率计算中的大多数硬件资源都致力于在两个或多个p位流之间生成特定的相关性。该项目将研究并展示一个系统，该系统将大大减轻与生成相关性相关的硬件负担。结果将使概率计算比目前更有效。该项目将教育该领域的K-12，本科生和研究生，以增加熟练的科学家和工程师的库，同时推进计算领域。概率计算中的主要挑战之一是在概率流中产生所需的相关性所需的复杂硬件。该硬件通常由微控制器，模数转换器，换档寄存器等组成，这些寄存器会消耗大量功率，并在芯片上大大扩展了系统的足迹。在这个项目中，将研究一个超紧凑且极其节能的相关器或抗相关器，并证明可以在两个P-PIT流之间产生可调的抗可相关程度。该方法是用两个磁性隧道连接（MTJ）实现的，这些磁力隧道连接处的软层紧邻，因此偶极耦合。位状态在MTJ的电阻状态（高或低）中编码。当由自旋偏振电流驱动时，一个MTJ会产生P-PIT。电流以由其大小确定的概率确定的电阻状态高或低，而另一MTJ的位状态是通过偶极子与第一个偶联来确定的。非常强的偶极子耦合将导致完美的抗相关性，而非常弱的偶极耦合将无相关性。偶极子耦合的效果将通过将（电产生的）局部应变应用于第二个MTJ来控制，该局部应变调节其内部能屏障，从而调节p-lits之间的抗相关程度从0％到100％至100％。该项目将使人们对使用新兴纳米磁物理学进行下一代计算的设备有了新的了解。该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响审查标准，通过评估被认为是珍贵的支持。

项目成果

Random Bitstream Generation Using Voltage-Controlled Magnetic Anisotropy and Spin Orbit Torque Magnetic Tunnel Junctions

• DOI: 10.1109/jxcdc.2022.3231550
• 发表时间: 2022-11
• 期刊: IEEE Journal on Exploratory Solid-State Computational Devices and Circuits
• 影响因子: 2.4
• 作者: Samuel Liu;J. Kwon;Paul W. Bessler;S. Cardwell;Catherine D. Schuman;J. D. Smith;J. Aimone;S. Misra;J. Incorvia