Quantum dots in photonic crystals: From quantum information processing to single photon nonlinear optics

Photons are attractive candidates for both quantum and classical information processing where they act as essential carriers of information and can greatly reduce the operating power, respectively. Efficient photon routing and switching devices are required for both applications, and necessitate the development of optical nonlinearities that work at single photon-single emitter levels. This work presents experimental and theoretical efforts toward the realization of nonlinear optical devices that operate at low photon numbers and reach single photon levels that are suitable for quantum information processing. We show that a single quantum dot coupled to a photonic crystal cavity can be used to realize a controlled phase gate between photons. In addition, this work also describes attempts at improving the operation of all-optical switches and modulators with the use of photonic band gap devices where the density of photon states is modified and tight photon confinement leads to enhanced field strengths. We show that the combination of cavities with standard nonlinearities can be used to realize fast optoelectronic modulators and switches. Finally we review efforts to combine this photonic technology with novel light emitters that operate at room temperature and have the potential to realize functional and cost effective quantum information processing devices. The main results of this work are the development of an experimental technique for coherent probing of a quantum dot inside a photonic crystal cavity and the realization of a controlled phase shift interaction between photons on the semiconductor chip. This interaction is enabled by the nonlinearity of a single quantum dot that is embedded in an optical microcavity.