A group of experimental physicists developed a device that behaves like a memristor while acting on quantum states and encoding and transmitting quantum information. The device is a quantum memristor. Creating such a device is difficult because the dynamics of a memristor defy usual quantum behavior.
The physicists have overcome the challenge by using single photons or single quantum particles of lights and exploiting their unique ability to propagate simultaneously in a superposition of two or more paths. In their experiment, single photons propagate along waveguides laser-written on a glass substrate, guided on a superposition of several paths.
The researchers measured the flux of photons going through the device via one of these paths. This quantity modulates the transmission on the other output through a complex electronic feedback scheme, thus achieving the desired memristive behavior.
Besides demonstrating the quantum memristor, the researchers have provided simulations showing that optical networks with the device can help learn classical and quantum tasks, hinting that the device may be the missing link between artificial intelligence and quantum computing.