Fibre-based memory module for photonic quantum computing

We are developing photonic quantum computers that will use individual particles of light known as photons to carry out computational tasks in more powerful ways than conventional supercomputers. However, operations in photonic quantum computers are fundamentally unreliable, hence memory elements are required to store successful outcomes of quantum logic gates until all have functioned correctly.

One way of storing light in a material system is by mapping the quantum state of a photon into a collective excitation of a cloud of atoms using an energy level transition mediated by a bright laser beam. The photon can then be retrieved a few hundreds of nanoseconds later by switching the laser on again. Although the storage time seems short, it is sufficient to buffer enough gates to build large-scale photonic quantum processors. Unfortunately, the atoms with the best energy levels for this application are rubidium -- a highly reactive element that is difficult to handle -- and existing quantum memories are limited by the characteristics of the vapour cells in which the rubidium must be contained.

In this project, we will design, build, and test advanced vapour cells that contain clouds of rubidium atoms in the hollow cores of special optical fibres. This will ensure not only that the reactive rubidium remains protected from the environment but also that light can interact with atoms over the whole length of the hollow fibre. Combined with the ease with which our compact fibre memory modules will integrate with other optical components, the products that we develop will enable a much larger number of memories be operated simultaneously at much higher efficiencies than was previously possible. This will open up new markets both within the scientific and technological development of quantum computation and beyond in the applications of photonic quantum computers to societal challenges including drug discovery, industrial process optimisation, or modelling new materials for batteries and solar cells.