Nanotube Stochastic Resonance: Noise–enhanced Detection of Subthreshold Signals

Noise can help signal detection at the nano–level. Experiments on a single–walled carbon nanotube transistor confirm that a threshold exhibits stochastic resonance: a judicious amount of noise can help a threshold–like nanotube transistor detect subthreshold signals while large amounts of noise overwhelm the signals. The nanotube produced this stochastic–resonance effect using three types of synchronized discrete–time white noise and two performance measures: mutual information and input– output correlation. Experiments in a cryostatic vacuum chamber added Gaussian, uniform, and impulsive (Cauchy) electrical noise. The electrical noise corrupted a random digital (Bernoulli) voltage sequence that acted as the subthreshold input for the nanotube transistor. The noisy signal stimulated the transistor’s gate and produced a sequence of random output (Bernoulli) current in the nanotube. Shannon’s mutual information and simple correlation measured the nanotube system’s performance gain by comparing the input and output sequences. Neither measure assumed any special nanotube structure. The observed nanotube SR effect was robust: it persisted even when infinite–variance Cauchy noise corrupted the signal stream. Such noise–enhanced signal processing at the nano–level promises applications to signal detection in wideband communication systems and biological and artificial neural networks.