Engineering Photonic Quantum States for Quantum Information

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

A single particle of light, or a photon, can be correlated with another photon such that measuring the properties of one instantaneously affects the properties of the other even if they are not in the same location. Such correlations make photons useful for creating new technologies that allow for faster and more powerful computing and completely secure communication as well as for testing fundamental physical theories. Yet creating photons with just the right correlations for such applications remains challenging. This research project addresses these difficulties by creating and demonstrating new techniques for measuring and controlling single photons and the matter with which they interact. By adjusting the energy source and medium in which photons are created, photons are created whose correlations are close to ideal for new technologies and fundamental tests of physics principles. It has been shown that single photons with properties suitable for secure long-distance communication can be stored in a memory made of a gas of atoms that preserves their correlations. In this project the interaction of light with the environment itself, such as how light is absorbed and transferred between different forms of energy in molecules, will be studied. The correlations of single photons will be used to gain more insight into how such processes occur. Extending the ability to control the properties of single photons and their interactions with matter has implications for creating new types of computing based on the laws of quantum mechanics that can solve otherwise prohibitive mathematical problems and simulate complex physical systems. It also enables methods of sending information completely securely, with clear indications of any eavesdropping, and improves the ability to test the theory of quantum mechanics. Understanding light-matter interaction in molecules supports the creation of new drugs and improvement of technologies that use such molecules. This research project also provides students training in quantum optics and atomic and molecular physics and informs the public about quantum technologies through demonstrations, museum exhibits and public lectures. This research project extends our understanding and ability to control the spatial and spectral-temporal properties of quantum states and their correlations. Quantum applications that utilize photonic quantum states often have specific requirements for the photons' spatial and spectral-temporal properties and correlations in order to perform protocols. Through this work new techniques will be developed and applied to measure with unprecedented speed and resolution the joint correlations of photonic quantum states produced via spontaneous four-wave mixing. The spectral tunability of photon-pairs created in artificially structured materials will be explored using a new scheme based on dual-pump spontaneous four-wave mixing. Photonic quantum states will be engineered using self- and cross-phase modulation and by tuning the group velocity difference between two distinct pumps, to create photon pairs that are completely uncorrelated (except for the existence of one indicating the other). Quantum memories, are critical components for quantum information processing applications. High-bandwidth storage and retrieval of telecom-wavelength photons using an off-resonant Raman protocol in atomic barium vapor will be demonstrated. The inherent correlations of the atomic system will be utilized to generate pure photons useful for quantum applications relying on high-visibility two-photon interference and demonstrate entanglement of atomic ensembles. Quantum information research has resulted in techniques to measure the spatial, spectral and temporal correlations of photonic quantum states. These techniques will be extended and applied to better understand and control the materials with which the photons interact. New spectroscopies based on single-photon level interference and coincidence detection will be used to gain unique insight into the coherence and population dynamics of molecular liquids, including the intricate redistribution of energy among vibrational states. By extending the understanding and ability to control ultrafast photonic quantum states and their interactions with material systems, the research contributes significantly to the goals of quantum information research in the areas of quantum communication, quantum computation, and fundamental tests of quantum mechanics. The new techniques demonstrated for quantum control in the spectral, temporal and spatial domains of photonic, atomic and molecular quantum states have the potential to open up exciting new avenues of research and technology development. The research is integrated with outreach components to inform the public and K-12 students about the amazing properties of single photons. The PI prepares interactive demonstrations of the applications of single photons in quantum communication for display in the University of Illinois physics building, and for presentation at public outreach lectures, engineering open houses, and for exhibit in a local children's museum. The research provides professional training to graduate students in quantum optics and atomic and molecular physics.