Hiding ignorance and finding knowledge: adventures using the shape of light

Speaker: Associate Professor Jacqui Romero
Affiliation: University of Queensland

Abstract

The transverse shape of light has emerged in recent years as a promising platform for encoding quantum information, for the multiple levels that it affords and the ease with which shape can be controlled. To demonstrate, I will discuss two recent experiments.  The first is on ignorance: One might ask if ignorance of a whole system implies ignorance of its parts.  Our classical intuition tells us yes, however quantum theory tells us no: it is possible to encode information in a quantum system so that despite some ignorance of the whole, it is impossible to identify the unknown part. I will give an experimental evidence that supports this counterintuitive fact.  The second is on learning: We used a tomographic technique inspired by machine learning to track a quantum state as the state changes. The method is computationally efficient and also robust—it converges to a good estimate even in the presence of strong noise.   Developing techniques like this is especially important for systems that are of high dimensionality, where making tomographically complete measurements become impractical.