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Topic Name: New paired-photon source
Category: Optoelectronics
Research persons: J. Fan, A. Migdall and L. Wang
Location: NIST Physics Laboratory,100 Bureau Drive, Stop 8400,Gaithersburg, MD 20899-8400, United States
Details
For a variety of applications in physics and technology, ranging from quantum
information theory to telecommunications, it’s handy to have access to pairs of
photons created simultaneously, with a chosen energy. In a significant
improvement on previous designs, physicists at the National Institute of
Standards and Technology (NIST) have devised a system that delivers such pairs
with great efficiency over a wide range of energy, and with very little noise
from extraneous photons*.
Paired photons can be generated—albeit very inefficiently—in standard optical
media such as glass optical fibers. Photons normally travel through glass
independently, without interacting, but if monochromatic laser light is sent
down even an ordinary optical fiber, very occasionally two of the input photons
will interact, producing an output photon pair with one higher in energy than
the original photons and the other lower by the same amount.
Because the vast majority of photons go through the fiber unchanged, the
relative intensity of these pairs is very small. Worse, the fiber generates the
pairs randomly with a range of possible energies, so picking out those with some
specific energy reduces the number of useful photon pairs still further. Worse
yet, there is noise in the system due to the phenomenon called “Raman
scattering,” in which individual photons bounce off the fiber’s molecular
structure and change their energies. Scattering produces photons that look
as if they might be one half of a pair, but aren’t.
To
beat these odds, the new NIST two-photon source relies on a microstructured
optical fiber. The fiber has a slender glass core at the center of an array of
hollow channels, giving it a honeycomb appearance in cross-section. The
geometrical structure of the fiber tightly restricts the way light can travel
down it, increasing the intensity of light in the thin central core. Higher
intensity means that photons are crowded more densely together, making events
such as pair production more likely.
That greater efficiency allows the NIST researchers to get significant
production of photon pairs by sending laser light through a mere 1.8 meters of
the microstructured fiber, in contrast to the hundreds of meters of ordinary
fiber that might be used in other systems. In addition, modifying the size of
the channels in the microstructured fiber allows its properties to be optimized
to reduce the amount of Raman scattering relative to the two-photon light of
interest. The result is a source that produces significantly more pairs of
photons over a wide frequency range, and with greatly reduced contamination by
spurious Raman photons.
Photon pairs from the new source could be useful, for example, in exploring
quantum “entanglement,” in which measurements on one of a pair of quantum
particles with a common origin exert a subtle influence on the properties of the
other, or in quantum cryptography
About researchers::
Fan,
Jingyun Dr. (Gaithersburg) -
jingyun.fan@nist.gov
name: Fan,
Jingyun Dr. (Gaithersburg)
phone: (301) 975-8112 agency:
NIST
address: 100 Bureau Drive, Stop 8441
:
Gaithersburg, MD 20899-8441
email: jingyun.fan@nist.gov
Last Updated: Fri Apr 13 2:30:08 EDT 2007
Migdall, Alan L Dr. (Gaithersburg) -
alan.migdall@nist.gov
name: Migdall, Alan L Dr. (Gaithersburg)
phone: (301) 975-2331
agency: NIST
address: 100 Bureau Drive, Stop 8441
: Gaithersburg, MD 20899-8441
email: alan.migdall@nist.gov
Last Updated: Fri Apr 13 2:30:08 EDT 2007
Lili Wang
NIST Building 227, Room A215
100 Bureau Drive
Gaithersburg, MD 20899-8312 USA
Phone: 301-975-2447
Email: lili.wang@nist.gov
Funded:
Funded by The Physics Laboratory,NIST.
The Physics
Laboratory is one of the major operating units of the National Institute of
Standards and Technology (NIST). Its mission is to support United States
industry by providing measurement services and research for electronic, optical,
and radiation technologies. The Laboratory
- pursues
directed research in the physical sciences;
- develops new
physical standards, measurement methods, and data;
- conducts an
aggressive dissemination program; and
- collaborates
with industry to commercialize inventions and discoveries.
The Laboratory
programs span the full range from tests of fundamental postulates of physics
through generic technology to the more immediate needs of industry and commerce.
Its constituency is broadly distributed throughout academia, government, and
industry
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