Josh Nunn

Myungshik Kim

NV Diamond Quantum Interface

In any practical architecture for quantum information processing (QIP), quantum photonics will no doubt play a key role - for instance, enabling the transmission of quantum information over large distances.

Since photons do not interact with one another, however, schemes to implement photon-photon interactions (necessary for computation) using linear-optical circuits make use of measurements with probabilistic outcomes and postselection for succesful results. As the probability of success for a series of gates falls exponentially with the size of the computation, in order for such protocols to be scaleable we seek a device which stores states following a successful outcome at each stage of the process would allow the user to actively synchronise elements from different stages of the operation using a “repeat until success” strategy for each stage.

Such a device is a quantum memory (QM), in other words, a system in which quantum states of light can be coherently stored and retrieved on demand. QMs are therefore a key element in the photonic QIP toolbox.

Particular applications of QMs would include synchronisation of single photons generated by spontanious paramatric down-conversion, or acting as repeaters in a large scale quantum network.

My project at Oxford builds upon previous experiments in a scheme for realising a single mode QM, based on Raman absorption of the signal field in room temperature atomic caesium.