Entangled states of atomic ensembles have the potential to overcome various limits in quantum measurements, including the so-called standard quantum limit associated with measurements on a collection of independent particles. To realize entanglement in a many-body system, internal states of cold, trapped atoms that are strongly coupled to laser light inside an optical resonator will be used. The photons inside the cavity act as messengers between distant atoms, and can be used to induce effective state-dependent long-range atom-atom interactions. These interactions, in turn, can be utilized to redistribute quantum noise so as to enhance the signal-to-noise ratio of atomic clocks and atom interferometers ("spin squeezing"). In this project we implement a modified spin squeezing method that allows one to disentangle the outgoing light from the atoms while maintaining the light-mediated atom-atom interaction. This new method provides not only much stronger spin squeezing than previously possible, it also enables the generation of non-Gaussian entangled states and even Schroedinger cat states in mesoscopic atomic ensembles. Furthermore, using the strong interaction between an atom and a mode of the optical resonator, we hope to demonstrate a variety of novel quantum optical devices, including a single-photon all-optical switch, a dispersive photon-number-state filter, and a deterministic quantum gate between two photons.
A major frontier of physics is the control of quantum mechanical many-body systems. Such control will enable novel devices for storing and processing quantum information, improve fundamental precision measurements, and enhance and deepen our understanding of key concepts of many-body quantum physics. Of particular interest is the quantum control of precision systems such as atomic clocks. Atomic clocks are the most accurate devices ever made by mankind, and have many important technological applications, including the Global Positioning System and telecommunication networks. This research program could significantly improve the precision of optical-transition atomic clocks beyond current limits, and enable many new technologies linked to the ability to precisely keep time. The project will train graduate students and undergraduate students. Exceptional high-school students will be integrated into the research effort. Efforts are made to include underrepresented minority students.
