Nature Nanotech. 9, 886–890 (2014)

Cavity quantum electrodynamics using semiconductors has attracted considerable attention as a convenient solid-state means for studying quantum systems. Real-time control of the radiative processes would offer an additional and useful degree of freedom for exploring the quantum properties of such a system. Chao-Yuan Jin and co-workers from Eindhoven University of Technology in The Netherlands and the Max Planck Institute for the Physics of Complex Systems in Dresden, Germany have now demonstrated such control for the first time, using a photonic crystal cavity with an embedded quantum dot that is coupled to an adjacent Fabry–Pérot cavity. By changing the refractive index of the Fabry–Pérot cavity, one of its modes can be brought into resonance with the mode of the photonic crystal. As a result, the Q factor decreases as the vacuum field is redistributed and the coupling and loss rates are modified. The main control was achieved by increasing the power (and thus the local heating) and inducing a redshift, and the dynamical control was demonstrated through free-carrier injection into the Fabry–Pérot cavity using pulsed excitation and zero detuning as a starting point. Such tunability is deemed to be extremely useful for modifying the properties of the quantum system (Rabi oscillations, for example) while leaving the cavity population undisturbed.