Granular nanoelectronics

Engineers have been proposing a new class of electronic devices that utilize quantum-mechanical principles (as opposed to classical principles) for their operation. These devices are often referred to as quantum devices or nanoelectronic devices since their physical dimensions are typically smaller than 100 nm. The granularity of electric charge (namely that it can be found only in quanta of a single electron's charge) is a quantum-mechanical property. Similarly, the granularity of an electron's "spin" (namely that only certain polarizations may be allowed) is also a quantum-mechanical property. These two "granular" properties are quite robust; they, therefore, show much promise in actual device applications. Ultrafast and ultrasmall electronic devices that utilize the granularity of electric charge (and an associated effect known as Coulomb blockade) have been proposed for years. Boolean logic gates, combinational circuits and sequential memory have been designed with them. "Single electron transistors" (SET) built on this concept have been demonstrated experimentally. A newly proposed class of Boolean logic gates utilize a single electron as the primitive logic element (a bistable switch). Physical wires between devices are replaced by quantum-mechanical spin-spin couplings which communicate signals across the chip. These are unusual features which distinguish a "quantum circuit" from a conventional classical architecture.