Semiconductor quantum dots combine many of the properties of atoms, such as discrete energy spectra, with the advantage that they can easily be embedded in solid-state systems. Moreover, quantum dots offer rich opportunities for generating non-classical light with "tunable" photon statistics. These properties make quantum dots attractive for novel device applications in the fields of quantum cryptography, quantum teleportation and quantum computation. As a result, physicists are devoting more and more effort into understanding the quantum optical properties of these systems.
Now two independent groups, led by David Gershoni of the Technion-Israel Institute of Technology in Haifa and Atac Imamoglu of the University of California at Santa Barbara in the US, have studied the emission of photons from a single semiconductor quantum dot as a function of time. Both teams measured the probability that a photon will be detected at a time tau + t after a photon had already been detected at an earlier time t.
In the March issue of Physics World, Peter Michler of the University of Bremen, Germany, describes how they have shown that it is possible to tune the way the photons are bunched together in time by changing the excitation power of the quantum dot (D Regelman et al. 2001 Phys. Rev. Lett. 87 257401; A Kiraz et al. 2002 Phys. Rev. B at press).