Quantum dots are man-made "droplets" of charge that can contain anything from a single electron to a collection of several thousand. Their typical dimensions range from nanometres to a few microns, and their size, shape and interactions can be precisely controlled through the use of advanced nanofabrication technology.
The physics of quantum dots shows many parallels with the behaviour of naturally occurring quantum systems in atomic and nuclear physics. Indeed, quantum dots exemplify an important trend in condensed-matter physics in which researchers study man-made objects rather than real atoms or nuclei. As in an atom, the energy levels in a quantum dot become quantized due to the confinement of electrons. With quantum dots, however, an experimentalist can scan through the entire periodic table by simply changing a voltage.
In this month's Physics World magazine (information), Leo Kouwenhoven of Delft University of Technology, the Netherlands, and Charles Marcus of Stanford University, US, describe how quantum dots make it possible to explore new physics in regimes that cannot otherwise be accessed in the laboratory.