CAREER: Quantum Measurements for Optical Communications

University Of New Mexico, Albuquerque NM

Investigators

Abstract

Optical communication enables high rates of information transfer over long distances. However, the amount of information that can be communicated is fundamentally limited by the intrinsic quantum noise of the states of light used as information carriers. This noise precludes any measurement from perfectly distinguishing different states and generates decoding errors. This project will investigate and experimentally demonstrate non-conventional measurements for coherent states of light, such as laser light, that exploit the properties of coherent states and single-photon detection to maximize the measurement sensitivity and enhance information transfer, and will develop methods to overcome noise, loss, and imperfections of real communication channels. These non-conventional measurements can in principle provide sensitivities beyond what is possible with current conventional technologies, and can be used to increase the rate of information transfer in optical communication. This project lies at the interface of optics, communication, and quantum information, and will provide an ideal environment for education of undergraduate and graduate students. The educational plan of the project will develop new experiments for laboratory courses at the University of New Mexico (UNM) that will strengthen the undergraduate and graduate curriculum. These new experiments will benefit undergraduate and graduate students in physics and optics including underrepresented minority students. Lab guides will be available online for use by students and instructors within and outside UNM. Quantum measurements for the discrimination of non-orthogonal coherent phase states can achieve sensitivities beyond the quantum noise limit (QNL), which corresponds to the ultimate limit for ideal coherent (Gaussian) measurements, and can be used to approach the ultimate quantum limits of information transfer. The goal of this project is to investigate and experimentally demonstrate new capabilities of measurements based on non-Gaussian operations for the discrimination of non-orthogonal coherent states for applications in quantum and classical communications. These measurements utilize photon counting, displacement operations and optimized adaptive measurements to enhance sensitivities for the discrimination of multiple states at arbitrary input power levels while being robust under realistic noise and loss of communication channels. These optimized methods can be applied to enhance the rate of information transfer in communications, and experiments will aim to demonstrate measurements with capacities beyond what is achievable with Gaussian measurements using coherent states. This work will make optimized measurements achieving sensitivities beyond the QNL a more realistic alternative to enhance information transfer beyond what can be achieved with conventional communication technologies.