Unit Quantum Efficiency, Nondestructive, Photon Counting Detector

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EIA-0323463John HowellUniversity of RochesterUnit Efficiency, nondestructive, photon counting detectorThe startling behaviors that have led to the dramatic slowing and stopping of light also have promise in the field of quantum information. Following a theoretical proposal by Schmidt and Imamoglu, an ultra-sensitive photon-counting detector is currently under construction. At the heart of this experiment is electromagnetically induced transparency (EIT). EIT allows a laser beam (probe beam), on resonance with an atomic transition, to pass unattenuated through an atomic gas of the relevant atoms. However, when a signal beam passes through the sample the EIT effects are dramatically changed. The effects are so strong that single photons in the signal field can change the macroscopic properties such as phase and attenuation of a classical probe beam. Nondestructively counting photons with high efficiency is of great interest to many quantum communications protocols. The experiment is in the construction phase. The electronics are being developed that will allow two New Focus Vortex lasers, one as the probe field and the other as the coupling field, to be locked to the top of a resonance peak in a Doppler-free saturated absorption spectrum of Rb 87. The effort is to achieve a linewidth stability on the order of 100 KHz or better for both lasers. The locked lasers will then be nearly collinearly passed through a relatively high buffer gas density vapor cell. Two sources for the signal photons are in production. The first source is from a third dramatically attenuated diode laser. The detector will project the otherwise Poissonian distribution of the signal laser into pure number states, which is an exciting result in and of itself. The second source is from narrow band entangled photons. Concurrent with the construction of the detector, is a narrow-band frequency-locked source of entangled photons, which is an important part of the test of this detector. Two women, three Hispanic and one African-American students are being trained under this project. The investigators are also heavily involved in Research Experiences for Undergraduates (REU) and undergraduate teaching.