A test conducted in Melbourne, Australia, demonstrated successful coexistence of classical and quantum
communication over fiber. Courtesy of QuintessenceLabs.
Yuan, the quantum key distribution project
leader. This self-referencing removes an
unwanted periodic signal that interferes
with sensitive detection of single photons,
enabling devices to recover faster because
the detectors are in a more favorable configuration.
“The detector can be moderately biased
for efficient single-photon detection, and
the detector recovery time is substantially
reduced. We have confirmed that the
detector recovery time is less than two
nanoseconds,” Yuan said.
These and other developments have
made quantum key distribution at acceptable data rates viable, said Grégoire
Ribordy, CEO of the Geneva-based ID
Quantique SA, a company commercializing the technology.
Unfortunately, the quantum nature of
the communication presents other hurdles.
For instance, it’s difficult to mix quantum
traffic with traditional telecom data. The
latter involves a multitude of photons,
and crosstalk from these can destroy the
single-photon signature.
One solution is to dedicate optical fiber to
quantum communication, but keeping fiber
dark for all other traffic is expensive. A possible solution is to spread the cost among
many users, something that can be done if
quantum key distribution is sold as a service
by a telecom provider, Ribordy said.
“They would offer an optical network
which would be shared by several QKD
systems. You can do wavelength division
multiplexing,” he said.
He noted that quantum key distribution
as a service is now a reality, with the first
customer using it announced in December.
Another firm involved in applications of
the new technology is MagiQ Technolo-
gies Inc. of Somerville, Mass. Because
quantum key distribution has yet to gener-
ate sufficient sales, companies are turning
to other revenue streams (see sidebar,
“Making More Money in the Meantime”
on p. 46).
A fully developed commercial entangled LED,
with an artist’s rendering of the entangled photon
pairs streaming forth. Courtesy of Toshiba Research
Europe.
Peaceful coexistence
Another advantage can be seen in a test
done with Telstra – Australia’s largest
telecommunications carrier – in Melbourne. In the test, one quantum channel
operated at one frequency. Running beside
it, but at another frequency, was a second
channel that carried synchronization and
timing information using classical
telecommunications.
“It offers the possibility of having
multiple quantum channels coexisting with
existing traffic,” Sharma said of this proof
of successful mixing of quantum and
standard communications.
In November 2011, QuintessenceLabs
partnered with prime defense contractor
Lockheed Martin to showcase its technol-
ogy. QuintessenceLabs also plans to bring
out a commercial product in the third
quarter of 2012.
