NSF BSF: Nonlinear Photon Interactions in Cooperative Quantum Optical Systems

Harvard University, Cambridge MA

Investigators

Abstract

One of the basic building blocks of quantum mechanics and quantum information science is the photon, the smallest possible amount of light. Unfortunately, photons can be made to interact (i.e., "talk to each other") only through matter. The implementation of such single-photon interactions is thus the topic of much fundamental and applied research efforts. Classically, interacting ("nonlinear") single photons constitute the fundamental limit of low-power optical switches, transistors, modulators, etc. On the quantum level, they provide the building blocks for quantum-enhanced technology and the so-called "third quantum revolution." The proposed work suggests 2D ordered arrays of atoms in traps. If these atoms are close enough to each other, they provide excellent effective photon interactions and are highly controllable. This project introduces a novel interaction platform that takes advantage of intrinsically nonlinear quantum media that can enhance single-photon nonlinearities such as cooperative and subradiant systems. Furthermore, adding an impurity to a cooperative 2D array allows light to couple to the medium, introducing a “quantum antenna.” Photons coupling to several such impurities can in this setup interact through the medium even stronger. Further enhancement can be reached through integration of Rydberg levels of the atoms or by additionally modifying the response of the material to display, e.g., a zero index of refraction. The questions that will be answered in this work are: (i) How can nonlinear material help create and harvest nonlinear interactions between photons? (ii) How, conversely, can photons be used to control cooperative materials? (iii) How can one implement these concepts experimentally and what applications are possible? Possible applications include quantum information processing, metrology, and quantum metamaterials, i.e., a class of materials exhibiting inherent quantum material response to light. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.