Cold atoms will be used to slow and stop optical images demonstrating a new technologically powerful technique for information management. The effort will include realizing an optical buffer or memory with the ability to load, store and retrieve weak and quantum transverse images. The combined expertise of Professor Howell's Slow Light and Quantum Optics group and the cold atoms experience and capabilities of Professor Bigelow's Cooling and Trapping group are ideally suited to achieve this goal. Encoded optical pulses will first pump a cold atom sample. Once the pump light is extinguished, the optical fields will have been interconverted to spin waves in the atomic medium, thereby storing the local electric field information of the pump. One key goal will be to stack images in the medium and then, using transverse excitation, pull out images one a time. There will also be studies to explore the capabilities of the system for making transverse entangled photons, which can then be stored in a similar medium. Preliminary studies indicate that microsecond pulses may have the possibilities of being stored for up to minutes.
It is expected that this research will make a significant contribution to the field of quantum information and image processing as it will provide a new means for information storage. There are also many aspects of the research which will be of fundamental interest to the broader community including: adiabatic pulse compression and decompression, image storage and distortion, transverse coherences and narrow bandwidth pulsed entangled photons. In addition to having impact on the frontiers of physics, the work will involve the training of the next-generation workforce in AMO physics and quantum information science. This training involves students at all levels: Professors Howell & Bigelow annually participate in the Research Experiences for Undergraduates program and the Research Experiences for Teachers program and both groups educate a diverse set of graduate students.
When attempting to understand the apparent bending of a straw in a glass of water or the focusing power of a lens, we learn about the index of refraction of a substance. In a simplified way, we can think of light moving more slowly in that substance. However, the index of refraction for every wavelength of light is different. It turns out that atoms can have very rapid changes in the index of refraction over a small range of wavelengths. With our NSF funding, we studied some of the effects of a rapidly changing index of refraction. Slow light has been one of these popular effects in which a pulse of light can be slowed from hundreds to trillions of times slower than the speed of light in vacuum. In this program, one of the things we showed is that we could create and turn off resonances in an otherwise transparent Rubidium gas. This demonstrated ability allows us to delay and then release, on demand, a pulse or even an image. We also showed that the rapid change in index in refraction in Rubidium gas could be used as a very strong dispersive prism (separating wavelengths very close apart). Everyone has seen the pretty rainbow that can be made by passing sunlight through a prism or wedged glass. The separation of the different colors of light from the sun can be used as a tool for scientists. While only over a small range of wavelengths, we built an atomic Rubidium prism with 100,000 times more dispersing power than a standard glass prism. This means we can separate very close wavelengths, which is useful for studying atomic emissions of light that are often difficult to study. Lastly, using slightly misaligned laser beams, we were able to create a standing wave in a hot Rubidium gas with tunable spacing. This standing wave caused a periodic index of refraction modulation. If another weak probe laser, on resonance with an atomic transition, is put into the gas, the laser observes a photonic bandgap and is reflected from the gas.
