Cavity based ion entanglement via fibre optic connections.

Quantum entanglement between qubits (embodied for example in atoms, ions, photons, or superconducting circuits) is one of the essential resources required for quantum information processing. However, entanglement generation is often inefficient and utilises a large range of optical components, limiting the scalability of quantum computation and communication schemes.

In this project we aim to overcome these limitations with the help of optical resonators coupled via optical fibres. In particular, we focus on systems that employ trapped ultracold ions to store quantum information. Placing the ions inside high finesse cavities leads to strong optical coupling between the ions and single photons, which can then be transmitted and exchanged via the optical fibre connections. Such schemes will allow for more efficient entanglement generation, thus reducing the number of redundant qubits required for error correction, better scalability, and more cost effective quantum devices.

For quantum communications the key to near deterministic entanglement is the use of pulse shaping techniques (such as controlled emission) to increase re-absorption by the second cavity. This project will look at how the single photon pulse shape affects this re-absorption after travelling ~100m - ~10km scale distances through a single mode fibre.

For quantum computation the key to efficient entanglement is to balance the coupling of a cavity - ion system, the reflectivity of the mirrors, and the overall losses in the system. For an efficient system these parameters should be optimised to give the maximum chance of success for entanglement.

The goal of this project is to look at both of these use cases for trapped ion systems to determine optimal parameters and the experimental limits of these systems.