Shaping up high-dimensional quantum information
High-dimensional quantum information using the shape of light has moved to the mainstream over the last few years. In this talk, I will provide a brief background of quantum information using the transverse shape of light. I will then focus on a recently published experiment on causality and quantum physics. In everyday life, it is natural to think of events happening in a fixed causal order--if we have two events, A and B, either A is before B, or B is before A. I will present an experimental demonstration of a device called a quantum switch, where the order of two operations depends on a control qubit, such that the statements "A is before B" and "B is before A" can both be true. I will then use this experiment to discuss the challenges that remain and how nanophotonics can help.