Neuromorphic computers process information in a similar way to brains. Conventional computers have separate memory and processor units, between which data must shuttle in a time- and energy-consuming fashion. Neuromorphic computers eliminate this by processing data and storing them in the same piece of hardware, as happens in a brain, where neurons and synaptic junctions contrive to do both jobs simultaneously. The field overlaps with biological computing.
The basic building block of a neuromorphic computer is the memristor—a component whose electrical resistance switches between high and low when a current is passed through it. Memristors can stand in for both neurons and synapses. To replicate a neuron, a memristor is combined with a capacitor. The capacitor acts as an adding machine for incoming current; once the charge exceeds a threshold, it discharges through the memristor, altering its resistance and permitting it to pass an electrical spike on to the wider network.
Perovskites are compounds with the chemical formula ABX3, where A and B are positively charged metal ions and X is a negatively charged non-metallic ion. They are named after a mineral discovered in the Urals in the 19th century. In a perovskite crystal lattice these ions are arranged into octahedra with large spaces between them, permitting other atoms to enter the crystal structure and change the material's properties.
Halide perovskites (where X is a chloride, bromide or iodide) can be engineered to have an electrical resistance that switches between high and low, making them suitable for use as memristors. Wolfgang Tress of Zurich University of Applied Sciences has developed artificial synapses using silver electrodes that encourage silver atoms to leak into the perovskite, forming highly conductive but fragile filaments. Bruno Ehrler of AMOLF, a physics-research institute in Amsterdam, has worked on combining memristors with capacitors to replicate neurons, and reckons a prototype network might be assembled as soon as 2027.
The tree of research must from time to time be refreshed with the blood of bean counters.