Experimental
set-up The rubidium atoms are trapped around the optical nanofiber and
absorb light of
wavelength 780 nm and 776 nm that has leaked out of the nanofiber.
This effect can be
used to create on/off switches.
(December 8, 2015) Researchers
in the Light-Matter Interactions Unit led by Professor Síle Nic Chormaic at the
Okinawa Institute of Science and Technology Graduate University (OIST) have
developed an on-off switch with ultrathin optical fibers, which could be used
for data transfer in the future. This research was published in the New Journal
of Physics.
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means “Physics is fun” in binary code. Computers translate every letter,
number, sign, space, image and sound to a set of 8 ones and zeros. For example,
01010000 corresponds to the letter P. While you type, your computer transfers
your words to another distant computer by sending a series of ones and zeros
encoded in light through standard optical fibers. Switching the light beam on
and off very quickly generates the ones and zeros. These bits of information
are converted to electronic signals at a node, usually a router or server, and
finally appear as text on the screen of your recipient. While this is the
classical way of transferring information online, OIST researchers are
exploring more efficient ways of transferring data, using the quantum
properties of light and matter. They have managed to create an on/off switch
based on the quantum characteristics of rubidium atoms in the presence of light
of different wavelengths. This proof-of-concept system could be used as a
building block in a quantum network, the future of our internet.
The OIST team’s experimental setup consists of two lasers
that produce light at different wavelengths, an optical nanofiber used to guide
light, and rubidium atoms trapped around it. The peculiarity of optical
nanofibers is their super-thin diameter. For this study the diameter was 350
nanometers, about 300 times thinner than the thickness of a sheet of paper. The
diameter is even smaller than the wavelength of the light guided by the fiber.
Some of the light, therefore, leaks outside the nanofiber and interacts with
the rubidium atoms that are trapped around it. These atoms can function as a
quantum node, a redistribution point of a network, the equivalent of today’s
servers.
Ravi Kumar, one of
the authors of this study, in front of
the machine used for the experiment
The off switch condition is obtained when only the laser
producing 780 nm is on. In this case, at the point where light leaks outside of
the optical nanofiber, the rubidium atoms absorb the maximum amount of light
and almost no light can continue to pass along the fiber. In contrast, the
switch is turned on when both 776 nm and 780 nm lights are present. In this
situation, most of the light is transmitted through the optical nanofiber and
the rubidium atoms absorb it only minimally.
Since the optical nanofiber is directly connected to a
standard optical fiber, the light can, in principle, be transferred to another
quantum system or node some distance away, in the same way you can send a
message from your computer to that of your friend’s in another location.