New life for conventional electronics

Modern electronics emphasizes miniaturization. Perhaps the most remarkable technological progress has come from reductions in the size of transistors, thereby increasing the number of transistors per chip. This number is predicted by the eponymous Moore’s law to double in about 18 months. However recently transistor technology approaches characteristic device sizes comparable to that of molecules, and correct description of the carrier dynamics requires the inclusion of quantum mechanical effects.

Nowadays quantum tunneling is widely used in tunnel field-effect transistors (FET) or tunneling diodes as well as in the floating gate operation in the flash memory technology. In today’s processor technology tunneling causes unwanted leakage currents, the main dissipation process and the limiting factor for the processor frequency. Due to this limitation, industrial companies cannot fulfill Moore’s law anymore without enhancing device and calculation complexity. Future technology will make use out of quantum effects without paying the price of the complexity increase. The quantum technology increases the level of control on the carrier transport and acts as a fundamental basis for applications in fast and high-performance devices.

Crucial applications of the quantum technology include high-speed switching devices while routing the signals between these devices is also of significant advantage. Both effects can be combined in ac-driven electron routers, that break the time reversal symmetry. The current generation of electron routers has large dimensions requiring sizes within the used operational wavelength (usually several centimeters) that is incompatible with nanoelectrical circuits. 

Devices such as Lissajous rocking ratchets offer an alternative solution while their size can be scaled down to a few nanometers. These devices combine well-known locomotion mechanisms of biomotors with elliptic Lissajous driving.

Here we presented its realization based on an ac driven quantum dot embedded in a semiconductor GaAs/AlGaAs heterostructure. Our Lissajous rocking ratchet encodes frequency, phase and amplitude information of the unknown signals in its dc-output and can be generalized to other fields of physics and biology.