Conventional logic and memory devices are built out of deterministic units
such as transistors, or magnets with energy barriers in excess of 40-60 kT. We
show that stochastic units, p-bits, can be interconnected to create robust
correlations that implement Boolean functions with impressive accuracy,
comparable to standard circuits. Also they are invertible, a unique property
that is absent in digital circuits. When operated in the direct mode, the input
is clamped, and the network provides the correct output. In the inverted mode,
the output is clamped, and the network fluctuates among possible inputs
consistent with that output. We present an implementation of an invertible gate
to bring out the key role of a three-terminal building block to enable the
construction of correlated p-bit networks. The results for this implementation
agree well with those from a universal model, showing that p-bits need not be
magnet-based: any three-terminal tunable random bit generator should be
suitable. We present an algorithm for designing a Boltzmann machine (BM) with
symmetric connections that implements a given truth table. We then show how BM
Full Adders can be interconnected in a partially directed manner to implement
large operations such as 32-bit addition. Hundreds of p-bits get precisely
correlated such that the correct answer out of 2^33 possibilities can be
extracted by looking at the mode of a number of time samples. With perfect
directivity a small number of samples is enough, while for less directed
connections more samples are needed, but even in the former case invertibility
is largely preserved. This combination of accuracy and invertibility is enabled
by the hybrid design that uses bidirectional units to construct circuits with
partially directed connections. We establish this result with examples
including a 4-bit multiplier which in inverted mode functions as a factorizer.

使用随机单元（如 p 位元）和混合设计实现了可逆的布尔逻辑门和 BM 加法器，同时保持了高度准确性和可逆性。