Important advances have been made in high-performance single-photon sources that bring such possibilities closer to reality. In particular, single photons can be used to implement absolutely secure optical communication, also known as quantum cryptography.
With this new source, recording a single-photon signature that took eight hours five years back can now be achieved on a millisecond time scale. This remarkable progress was achieved by developing a novel type of microcavity structure which strongly enhances the light extraction from the optically active material.
Moreover, with the help of embedded electrical gates, the researchers demonstrated suppression of unwanted dead-times in the emission process itself resulting in a net single photon generation rate of 100 MHz into an optical fiber.
Stefan Strauf, Assistant Professor in the Department of Physics & Engineering Physics at Stevens Institute of Technology, along with colleagues from the University of California, Santa Barbara and Leiden University (Netherlands), has authored the article, "High-frequency single-photon source with polarization control," the cover article of the December 2007 issue of Nature Photonics.
Strauf said "The traditional approach to generating single photons is to use weak laser pulses. In order to reach the single-photon level, you have to attenuate the light very strongly, limiting the efficiency of the device. Also, the photons emitted are governed by statistics. What we need is a high-efficiency source where we can generate photons one by one. Luckily, nature provides a solution in the form of the two-level system, just like the one we use: self-assembled quantum dots," said Strauf.
As described in the News & Views section of the issue, "More futuristic applications of single photon states include photonic networks designed to achieve scalable quantum computation, which one day will hopefully solve problems exponentially faster than classical computers."
Strauf's coauthors on the paper are Nick G. Stoltz (Materials Department, University of California, Santa Barbara); Matthew T. Rakher (Department of Physics, University of California, Santa Barbara); Larry A. Coldren (Materials Department and the ECE department, University of California, Santa Barbara); Pierre M. Petroff (Materials Department and the ECE department, University of California, Santa Barbara); and Dirk Bouwmeester (Department of Physics, University of California, Santa Barbara and Huygens Laboratory, Leiden University, the Netherlands).
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