Quantum engineering of matter from the laboratory to the market: an interview with Dieter Bimberg and Kang Wang

Abstract

Abstract Quantum dots introduce a new form of quantum engineering of materials properties based purely on size and dimensionality. Whereas we traditionally think of materials as having intrinsic properties such as strength, electrical conductivity and light absorption or emission spectra due to their composition and atomic-scale structure, when their size is very small, such properties can be altered by quantum-mechanical effects, for example due to confinement of the quantum wavefunctions that determine the energies of charge carriers like electrons. As it became possible in the 1990s to control the size of material structures with a precision of less than a nanometre in all three dimensions of space, quantum effects began to be exploited for technological applications. Quantum dots are particles with a nanoscale extent in three dimensions—in effect, tiny fragments of material, often made of one type of semiconductor embedded in another. Quantum dots in which the wavelength of absorption and fluorescent emission of light is tuned by the nanoparticle size are being explored for uses ranging from colour displays to biomedical imaging. Films of semiconducting materials thin enough to exhibit one-dimensional quantum-confinement effects, meanwhile, are routinely used to make efficient optical devices such as lasers. Such applications have depended on the availability of techniques for precise control of particle size, composition and thickness. NSR spoke to two leading researchers in this field of quantum engineering about its development and prospects. Dieter Bimberg is founding director of the Center of Nanophotonics at the Technical University of Berlin in Germany. He pioneered the use of quantum dots in photonic devices such as lasers and optical amplifiers, as well as developing non-volatile ‘dynamic’ random-access memories (DRAMs), which retain their information when the power is switched off. Kang Wang is a professor of electrical engineering at the University of California at Los Angeles, whose work on nanoscale quantum devices has focused on electronic and magnetic properties, and in particular on the development of non-volative RAMs and the manipulation and control of electron spin as a new parameter for information processing (a technology called spintronics).