This research program aims to demonstrate high-efficiency storage and retrieval of light pulses while preserving the quantum state of the photons. Such quantum memory for photons can be realized by mapping the quantum states of light to the collective excitation of spins inside an ensemble of identical atoms using a dynamic form of electromagnetically induced transparency. Some essential elements of practical quantum information "toolbox" will be developed, including universal quantum memory optimization techniques, low-loss/high-rejection optical filters, and sources of single photon pulses and continuous light with non-classical statistics ("squeezed light" or "squeezed vacuum") based on both nonlinear atomic media and high-quality crystalline microresonators.
These experiments will have significant educational and scientific broader impacts. Most of the experimental results are applicable for wide variety of atomic, solid-state and photonic systems, and an ensemble of warm rubidium atoms will serve as a prototype interaction medium, and they will advance practical realization of quantum information technologies, such as quantum repeaters. The other broader impact of the program is involvement of undergraduate and graduate students at different levels in cutting-edge scientific research, and educating them about basic concepts of atomic physics, quantum optics and quantum information science.
The goal of the program was to expand and improve the "toolbox" of experimental techniques that utilize atoms and light that scientists can use to implement quantum mechanical protocols. There were three specific goals: to demonstrate and improve a robust atom-based soars of quantum optical field (i.e. an optical field that cannot be completely described by the laws of classical physics; to improve the performance of quantum memory, in which a quantum state of light could be transferred to a collective ensemble of atoms and preserved for up to a millisecond before transferring it back to atoms; and finally to investigate the possibility to produce squeezed light using whispering gallery optical modes propagating inside a disc-shaped nonlinear crystal. We have achieved a significant progress in all direction which was the main intellectual merit. Specifically, we have developed a practical source of "squeezed vacuum", an optical field with modified quantum fluctuations that allows (with proper measurements techniques) to mitigate the unavoidable noise due to phase-amplitude Heisenberg uncertainty. To illustrate the advantage of such squeezed light, we used it to build a magnetometer prototype with 50% lower noise and better sensitivity compare to a standard laser source. We have advanced understanding of quantum memory, based on electromagnetically induced transparency, in which a strong control optical field eliminates usual absorption of a weak optical signal and creates a strong connection between its quantum state and a collective spin state of atoms. We demonstrated the efficiency of such a quantum memory up to 50% for arbitrary shaped optical pulses, and indicated an important nonlinear mechanism (resonant four-wave mixing) that prevents further improvements. Finally, using several hand-polished lithium niobate disks using a 1064nm pump laser we have achieved second harmonic generation at 532nm and several yellow-shifted hyper-Raman sidebands in wide range of temperatures far from phase matching conditions. The broad impact of this project is its various educational activities. There are four graduate students and sixteen undergraduate who were supported by this project, that lead to one Ph.D. and 7 BS senior theses. All graduates and most undergraduate students had presented their results in various regional and international conferences. To make our research progress available for educational purposes, we have published a paper in American Journal of Physics describing the experimental setup for observation and studies of Electromagnetically Induced Transparency and EIT-based atomic clocks. To further promote scientific education and inform public about scientific advances, PI with a group of undergraduate students have started an annual open house at the Physics Department of William and Mary, that attracts more than 200 people each year. She also established contacts with several local schools for organization of regular hand-on experiments and demonstrations.
