Quantum information processing and communications are new and exciting research fields that have currently attracted much attention. These techniques enable the faithful transfer of unknown quantum states, truly secure transmission of secret messages and even faster computation by directly utilizing quantum mechanical phenomena, which are unable or difficult to be achieved on the basis of classical mechanics. Furthermore the growth of quantum information technology makes it possible to observe new quantum phenomena, for example "quantum entanglement", which promises a full understanding of quantum mechanical phenomena.
Light is the most suitable system to transmit quantum information, since it maintains the quantum coherence for the longest time. However, light has some drawbacks in that it is difficult to be stored and to implement quantum gate operations. Therefore, it is strongly desired to realize "quantum memory (QM)" in the near future. QM plays an important role in transfer, storage, manipulation, and retrieval of the quantum state of light on demand. QM promises a breakthrough for implementations of optical quantum networks and optical quantum computers. Furthermore, the faithful transfer of the quantum state between light and a material gives a chance to observe novel macroscopic quantum states of material, for example quantum entanglement via light between spatially separated materials. This would break a novel exciting research field, namely quantum light-matter physics.
It is required to realize solid-state QM which has many advantages to make QM devices, though the research of QM goes ahead in demonstration in atomic systems so far. Generally, it is much difficult to transfer quantum states between light and solid states with high fidelity, because the quantum state is very fragile to loss. Therefore, it efficiency remains an important and big challenges.
The aim of this project is to develop a new technology to implement optical QM using semiconductor quantum dots which are known as artificial atoms. I try to prove the principle of new QM technique via a photon echo process using ultrashort optical pulse sequence whose phase is highly controlled. This technique is much different from previously demonstrated QM techniques utilizing electromagnetically induced transparency. Moreover, a new method and sample structure to increase optical nonlinearity will be developed for QM operations with weak light. |