Quantum dot spins in photonic structures for quantum information applications

Single photons are the cornerstone of linear-optical quantum computing their unique quantum-mechanical properties mean that they may be produced in superposed and entangled states that form the basis of a quantum bit. A quantum computer, however, also requires a way to store the information in a photon superposition for longer times: a quantum 
memory is needed. 

While photons are very difficult to store for times more than a few picoseconds, a much better solution is to transfer the photon information into a single electron spin.  In this talk I will discuss the techniques required to achieve this.  I will show that electron spins are in principle able to store photon information for microseconds, by using a semiconductor nanostructure known as a quantum dot.  I will then discuss the necessity to embed the quantum dot inside a photonic structure to increase the efficiency of the photon-spin 
interface.  I will discuss micropillar structures used in Bristol University to achieve this, and then highlight the advantages and disadvantages of other systems, such as photonic crystal cavities and metal optical nanoantennas.  Finally I will discuss the complications arising from focusing of polarized light on the nanoscale and the fundamental physics that arises.