Quantum Interference Devices

Abstract

Since 1985 experiments on submicron metallic and semiconducting structures have revealed three interrelated quantum effects: The Aharonov-Bohm effect, conductance fluctuations and non-local effects. The objective of this chapter is to explore theoretically the device implications of these exciting developments. The primary emphasis (Sect. 10.2) is on a new device concept based on the Aharonov-Bohm effect, where the current is modulated by controlling the quantum mechanical interference between alternative channels or paths connecting the source and the drain. The phase difference between the paths can be changed by π with a small potential difference (1 mV) so that a transistor based on this concept is expected to have high transconductance and low power dissipation. In Sect. 10.3 we discuss the possibility of quantum circuits relying on interference effects to implement individual resistors or resistor networks that can be programmed by a remote gate through non-local quantum effects. Though many hurdles remain to be overcome before these exotic devices become practical, the real power and utility of quantum devices may ultimately lie not in the implementation of conventional transistors having a source, a drain and a gate (where the low current capability is a major concern) but in the implementation of programmable multi-terminal quantum networks that could lead to radically new concepts for information processing with electronic devices.