Single-photon detector array technologies have advanced significantly in recent years. Cameras now exist that are not only sensitive to single photons but the individual pixels in the sensor provide photon time-of-arrival information the picosecond regime. Such unprecedented sensitivity and temporal resolution opens up a number of exiting new applications, such as light-in-flight imaging, looking around corners with laser echoes, and seeing through dense scattering media. I will discuss the recent developments of the camera technology and discuss our latest results. I will give details of our latest field trials, where we have been using single-photon detector array sensors to see through fog and smoke. I will also discuss our latest results for high-speed imaging in three dimensions. The latest sensor is able to capture 3D data at frame rates greater than 1000 frames per second. This technology is relevant for the analysis of rapidly changing systems where three dimensional information is necessary.
Since its first demonstration in 1995, ghost imaging has provided amazing insights into both classical and quantum physics as well as having found application in, for example, microscopy and imaging under low light conditions. Traditional ghost imaging uses correlations between two photons to reconstruct an image of an object from two systems which each individually know nothing about the object. In the quantum case, the state of the two photons is typically a symmetric, entangled state. Here we investigate the effect that changing the two-photon state's symmetry has on the reconstructed object, by using Dove prisms and a Hong-Ou-Mandel filter. Interestingly, it appears that post-selecting on the anti-symmetric Bell state results in a `double image': a juxtaposition of the original image rotated both clockwise and anti-clockwise. Furthermore, we consider a 4-photon experiment in which two photons, which originate from different entanglement sources and are hence completely independent initially, acquire correlations by way of entanglement swapping via appropriate post-selection on the remaining two photons. In such a setup, post-selecting on the symmetric Bell states results in the original object, but post-selecting on the anti-symmetric Bell state results in a contrast-reversed image of the object. These studies highlight the fundamental importance that state symmetry plays in quantum imaging.