Quantum Measurements for Continuous-Variable States with Photon Counting

University Of New Mexico, Albuquerque NM

Investigators

Abstract

Measurement of the state of an optical field is at the center of many technological applications across physics and engineering including optical communications, sensing and metrology, and information processing. When the optical state encodes information, optimal or near optimal measurements allow for decoding this information efficiently and reliably, enhancing the performance of different protocols in communications and information processing. The design and optimization of measurements critically depend on the intrinsic properties of the optical states and the available resources in the measurement to be realized. This project will investigate optimal and near optimal quantum measurements for optical states comprised of coherent states (light from lasers) and state superpositions, based on photon counting measurements and optimized coherent displacement operations. Optimized measurements for coherent states and their superpositions can provide a new tool for protocols in all-optical quantum information processing and long-distance quantum communications. Furthermore, the design of efficient quantum measurements for optical quantum states is essential for current and future developments in photonic quantum technologies, which are the subject of many academic and industrial efforts worldwide. Quantum measurement theory provides a fundamental understanding of the limits on the achievable sensitivity for determining the states of quantum systems. This project will demonstrate optimized quantum measurements for coherent states and their superpositions for applications in quantum communications, information processing, and computation. These optimized measurements are based on photon counting, coherent displacement operations, and adaptive measurements, which will allow for the design of a wide class of optimized quantum measurements for diverse states and measurement problems. The proposed quantum measurements of coherent states seek to realize complex projective and non-projective measurements with fidelities and sensitivities for state projection and discrimination beyond the reach of standard measurement paradigms including Gaussian measurements (homodyne/heterodyne). The project will advance new knowledge through the development of experimental techniques for ultrasensitive optical measurements with high fidelity, and through theoretical methods for the design and optimization of complex quantum measurements with finite resources. Theoretical efforts will focus on quantum measurements of coherent states and their superpositions based on photon counting, coherent displacements, and adaptive strategies. Experimental efforts will focus on the demonstrations of these strategies in tabletop experiments. 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.