Quantum Memory

Develop a memory so powerful, you're like a human computer. Learn how to remember names, faces, numbers, birthdays, dates, appointments, or any sequence of numbers you want. Dominic O'Brien is renowned for his phenomenal feats of memory and for outwitting the casinos of Las Vegas. He is barred from playing Blackjack in all UK casinos. A bestselling author of You Can Have An Amazing Memory and How to Develop a Brilliant Memory Week by Week, he has won the World Memory Championship eight times.

This thesis presents an experimental study of quantum memory based on cold atomic ensembles and discusses photonic entanglement. It mainly focuses on experimental research on storing orbital angular momentum, and introduces readers to methods for storing a single photon carried by an image or an entanglement of spatial modes. The thesis also discusses the storage of photonic entanglement using the Raman scheme as a step toward implementing high-bandwidth quantum memory.

Ultra-cold atomic ensembles have emerged in recent years as a powerful tool in many-body physics research, quantum information science and metrology. This thesis presents an experimental and theoretical study of the coherent properties of trapped atomic ensembles at high densities, which are essential to many of the aforementioned applications. The study focuses on how inter-particle interactions modify the ensemble coherence dynamics, and whether it is possible to extend the coherence time by means of external control. The thesis presents a theoretical model which explains the effect of elastic collision of the coherence dynamics and then reports on experiments which test this model successfully in the lab. Furthermore, the work includes the first implementation of dynamical decoupling with ultra-cold atomic ensembles. It is demonstrated experimentally that by using dynamical decoupling the coherence time can be extended 20-fold. This has a great potential to increase the usefulness of these ensembles for quantum computation.