Two Fundamental Forms of Quantum Optical Entanglement: Their Relationships, and Their Equivalences in Certain Measurement Contexts

An enduring, foundational question in quantum optics is whether entanglement between optical photons—namely, the particles of light—is equivalent to entanglement between their characteristic field modes. Typically, these modes are modeled using single-particle wavefunctions that are suitably composed and superposed, so as to describe identical particles within such modes. In my talk, I will approach this problem, in a novel manner, by describing a situation in which the entangling interactions between optical modes are distilled into genuine entanglement between the wavefunctional—that is, physical—degrees of freedom of the photons. This distillation is accomplished by making measurements on an ancillary photon. This measurement process—specifically, the detection of the ancillary photon—controls an anharmonic potential that is essential for creating the final entangled state of photons. This theoretical observation might be applied to formulate a new class of protocols for performing quantum information tasks using entangled photons within inseparable field modes. I will also describe several consequences of non-ideal photo-detection efficiencies, and how these limitations might be overcome. Finally, I will compare and contrast the above scheme with standard entanglement swapping procedures.