Energy-Efficient Stochastic Computing with Superparamagnetic Tunnel Junctions

Abstract

Superparamagnetic tunnel junctions have emerged as a competitive, realistic nanotechnology to support novel forms of stochastic computation in CMOS-compatible platforms. One of their applications is to generate random bitstreams suitable for use in stochastic computing implementations. We describe a method for digitally programmable bitstream generation based on pre-charge sense amplifiers which is more energy efficient than previously explored alternatives. The energy savings offered by this digital generator survive when we use them as the fundamental units of a neural network architecture. To take advantage of the potential savings, we codesign the algorithm with the circuit, rather than directly transcribing a classical neural network into hardware. The flexibility of the neural network mathematics compensates for explicitly energy efficient choices we make at the device level. The result is a convolutional neural network design operating at ≈ 150 nJ per inference with 97 % performance on MNIST-nearly an order of magnitude more energy efficiency than comparable proposals in the recent literature. * matthew.daniels@nist.gov † mark.stiles@nist.govThe low energy, truly random behavior, ease of control, and established compatibility with complementarymetal-oxide-semiconductor (CMOS) circuitry has led to the use of SMTJs as the basis for a number of novel computing schemes [11][12][13]. SMTJs were proposed to implement the concept of probabilistic bits, or "p-bits," which were leveraged for applications as Bayesian neural networks [14][15][16], invertible Boolean logic [17,18], reservoir computing [19], and Ising network models applied to optimization problems [20,21]. SMTJs were also proposed as stochastic neural units [22] that can interact with synaptic units, emulated by crossbar arrays of mag-

Voltage Controlled Domain Wall Motion based Neuron and Stochastic Magnetic Tunnel Junction Synapse for Neuromorphic Computing Applications

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Noise suppression beyond the thermal limit with nanotransistor biosensors

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Electrically programmable probabilistic bit anti-correlator on a nanomagnetic platform

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