One of the great successes of quantum physics is the description of the long-lived Rydberg
states of atoms and ions. Of particular interest, because they can be employed in quantum control of one atom by another, are excited Rydberg states, where wavefunctions are expanded from their ground-state extents of less than 0.1 nm to several nanometers and even beyond; this allows atoms far enough apart to be non-interacting in their ground states to strongly interact in their excited states. For eventual application of such states, a solid-state implementation is very desirable. I demonstrate here the coherent optical control of impurity wavefunctions in the most ubiquitous donors and acceptors in silicon. In our experiments, I take advantage of a terahertz radiation from a free-electron laser to stimulate and observe population lifetimes, photon echoes for coherent lifetimes - the orbital analogue of the Hahn spin echo, and Rabi oscillations familiar from magnetic
resonance spectroscopy. As well as extending atomic physicists’ explorations of quantum
phenomena to the solid state, the work adds coherent terahertz radiation, as a particularly precise regulator of orbitals in solids, to the list of controls, such as pressure and chemical composition, already familiar to materials scientists.
[1]. N. Q. Vinh, et al., P. Natl. Acad. Sci. USA 105, 10649 (2008)
[2]. P. T. Greenland, et al., Nature 465, 1057 (2010).