Quantum concepts have begun to invade classical optics and surprising results are being reported for coherence and entanglement. This is due to the fact that the mathematical structures of multiple independent degrees of freedom and their superposition properties are strictly analogous for a quantum wave function comparing to a classical light field. We have examined the unexplored territory of entanglement between the temporal and transverse spatial (time-space) degrees of freedom of a light beam. Surprisingly, this has led to the discovery of a generalized "polarization" and has consequently provided a new and comprehensive view of coherence. We have designed a novel spatial mode tomography apparatus and carried out experiments to obtain first quantitative measures of this new "polarization" with a Poincare sphere representation.

Dr. Xiaofeng Qian received his Ph.D. degree in physics from the Department of Physics and Astronomy, University of Rochester in April 2014. He then became a Visiting Scientist and subsequently an Instructor/Fellow at the same institute. Since July, 2015 he was employed as a Research Associate by the Institute of Optics, University of Rochester. His research focuses on both theoretical and experimental issues in quantum physics and coherence optics.