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Topic Name: A new prototype high-speed quantum key distribution (QKD) system
Category: STAR (Space, Telecommunications & Radioscience)
Research persons: H. Xu, L. Ma, A. Mink, B. Hershman and X. Tang
Location: 100 Bureau Drive, Stop 8423,Gaithersburg, MD 20899-8423, United States
Details
Researchers at the National Institute of Standards and Technology (NIST) have built a
prototype high-speed quantum key distribution (QKD) system, based on a new
detector system that achieves dramatically lower noise levels than similar
systems. The new system, they say, can perform a theoretically unbreakable
“one-time pad” encryption, transmission and decryption of a video signal in
real-time over a distance of at least 10 kilometers.
Key distribution—Quantum
Information Networks-the problem of
ensuring that both the sender and receiver of an encrypted message (and no one
else) share the same long string of random digits (the so-called “key”) used
to encode and decode the message—has always been one of the most important
challenges in cryptography. Since the 1980’s it’s been recognized that the
unique properties of quantum mechanics—the fact that certain measurements
cannot be made without altering the thing measured—offered the possibility of
a system that could transmit as long a key as desired between two parties with
no chance that it could be copied undetectably by a third party.
Since then the race has
been on to build a fast, practical and reliable QKD system. One important
requirement for any candidate system is that it be compatible with existing
fiber-optic telecom networks that transmit at wavelengths of either 1550 or 1310
nanometers (nm) to reach the greatest distance. Another requirement is a highly
efficient photon detector that can detect single photons reliably without
introducing significant amounts of “noise.” One of the best low-noise
detectors, a silicon-based avalanche photo diode (Si-APD), does not function at
the telecom wavelengths. Instead, it operates best at much shorter wavelengths
around 700 nm. To take advantage of the Si-APD, the NIST group designed a
sub-system to “up-convert” single photons from a transmission wavelength of
1310 nm to 710 nm for high-efficiency detection.
Their QKD system that
incorporates this up-conversion technique, described in a recent paper,*
generates and transmits secure keys at a rate of over half a million bits per
second over 10 km of optical fiber, fast enough to encrypt streaming digital
video using one-time pad in real time. The group also has transmitted secure
keys at rates near 10 kilobits per second at five times that distance. The same
team last year set a speed record for transmission of secure keys over a
kilometer of fiber (see www.nist.gov/public_affairs/releases/quantumfiber.htm).
This work improves the distance by at least 10 times.
Advantages of the new
system, according to the research team, include high speed, high efficiency, low
noise and convenience of operation. The fact that it uses a 1310 nm transmission
wavelength somewhat limits the propagation distance but adds the advantage that
the parallel “classical-quantum” communication, which is needed for a full
QKD system, can be realized in a single fiber without significant interference.
About Researchers-
Dr Alice Xiao-Jing Tang
BSc Material Protection
PhD Biosensors
Managing Editor of Biosensors & Bioelectronics, Elsevier
Managing Editor of the journal, Biosensors & Bioelectronics, Cranfield Health
Tel:+44 (0) 1525 863032
email: a.tang@cranfield.ac.uk
Mink, Alan (Gaithersburg) -
alan.mink@nist.gov
Mink, Alan (Gaithersburg)
phone: (301) 975-5681
agency: NIST
address: 100 Bureau Drive, Stop 8920
: Gaithersburg, MD 20899-8920
email: alan.mink@nist.gov
Last Updated: Fri Jun 15 2:30:07 EDT 2007
Funded:
Workshops
on Quantum Information Science and Emerging Technologies
In The Images
Detection stage of the
NIST prototype quantum key distribution (QKD) system: Photons are
“up-converted” from 1310 to 710 nm by one of the two NIST-designed
converters at right, then sent to one of two commercial silicon avalanche photo
diode units to the left.
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