Technology at the quantum limit promises significant advances in computing, communication, sensing and metrology, and imaging. The UK and many other countries around the world have recently provided significant investment in the development and realisation of such quantum technologies. In this talk, I will highlight my group’s activities in applied and fundamental quantum science, specifically focussing on advances in communication, imaging, and metrology. Much of our work relies on the detection of single photons via single-photons detectors, either in single-point or array formats. Such detectors enable unprecedented sensitivity to light and allow precise detection of arrival times, down to picosecond timescales. This is the key enabling feature that allows us to see around corners, detect objects through scattering media, and generate entanglement between photons that have never interacted.
In my talk, I will discuss in detail our work on entanglement swapping; this generates remote quantum correlations between particles that have not interacted and is the cornerstone of long-distance quantum communication, quantum networks, and fundamental tests of quantum science. The system is based on a new quantum protocol using a degenerate filter that cannot distinguish between different anti-symmetric states, and thus entanglement swapping occurs for several thousand pairs of spatial light modes simultaneously. I will also discuss a mechanism that allows high-dimensional entanglement swapping with only four photons, removing the need for scaling photon numbers with dimensions.