Towards Quantum Teleportation from a Spontaneous Parametric Down-Conversion Source to a Quantum Dot Spin by Hong-Ou-Mandel Interference.

Abstract

In this thesis, we will discuss results on quantum optical measurements in InAs self-assembled quantum dots (QDs). A single electron confined to a QD provides an attractive ground state qubit for many quantum information architectures. The excitation of an exciton in the QD structure via optical radiation will produce an electron-hole pair and, when combined with the ground state electron, form a quasi three-particle state called a trion. The trion transitions allow us to optically manipulate and readout the spin state. Narrow linewidth continuous wave lasers are used to probe the properties of the trion transitions in the frequency domain. We recover atomic like behavior for the QD resonances. The time dynamics of the trion system are studied by time gating a CW laser with an electro-optic modulator (EOM) and time tagging the scattered single photons from the transition using single photon detectors. These techniques are utilized in an entanglement protocol where a photon emitted during decay from the trion state to one of the electron spin states creates an entangled state between the electron spin and the photon. Under the influence of a transverse magnetic field the optical transitions from the spin states to the trion states are orthogonally polarized. The entangled state we are demonstrating is between the polarization state of the photon and the polarization state of the electron spin. We extract a corresponding fidelity of 0.6. The entangled nature of the spin state and the photon allows for the possibility to transport entanglement by means of this photonic channel. We study the coherence properties of the emitted photon using Hong Ou Mandel interference, which shows the indistinguishability of the photons (a required property for quantum information transport). Finally, we develop an experimental protocol to teleport quantum states from cavity enhanced photon pairs created in spontaneous parametric down conversion (SPDC) to a QD spin state by the interference between entangled photons from the QD and the SPDC photons.