Photon Blockade with Memory and Slow Light using a Single Atom in an Optical Cavity
Haytham Chibani
Abstract
The realization of nonlinear systems able to mediate strong interactions between light fields at the few photon level in an environment with minimal absorption represents a cornerstone for future developments of quantum information science and photonic quantum technologies.One approach to reach this goal is via strong coupling of single emitters to optical cavities as provided by cavity quantum electrodynamics (QED).The other one is via electromagnetically induced transparency (EIT) with single atoms or with atomic ensembles.This thesis reports on a system which merges both single-atom cavity QED in the strong coupling regime and EIT.First, we characterize this system theoretically and show that its energy eigenstates are very similar to the well known Jaynes-Cummings ladder of eigenstates.However, here, the eigenstates are optically controllable via the control field Rabi frequency provided by EIT.We show that increasing the control field Rabi frequency enhances the normalmode splitting, and therefore the effective light-matter coupling.Moreover, with this system we are able to observe photon blockade and a two-photon gateway for the same input probe field and to tune the behavior of the secondorder correlation function optically.Thanks to the long coherence times of EIT, photon blockade can be prolonged in time for longer times than the decay rates of the system.We refer to this effect as photon blockade with memory.Next, we verify our theoretical findings experimentally.By performing spectroscopy measurements on the single-atom cavity EIT system, we show an unprecedented EIT on/off contrast of about 80 % thanks to our strong atomcavity coupling rate.Later, we show experimentally, the ability to generate both, photon blockade and a two-photon gateway, for the same input field by just varying the control field Rabi frequency.Finally, by performing timedependent second-order correlations we observe strong oscillations in the correlations which are a result of the creation of a new light field in the cavity which beats with the impinging probe laser.We show experimentally that this new field has a coherence time longer than the decay rates of the system, confirming its EIT origin.In a final experiment, we take advantage of the strong atom-cavity coupling achieved to induce a group delay on probing pulses.Delays up to approximately 200 ns are measured.This is the first time a group delay is observed with a single atom as the delaying medium.iii