IEEE Spectrum March, 2007 - 10

Commercializing
Quantum Keys

companies link spooky techniques to off-the-shelf
distribution technology

hArry CAMpBEll

It's a strange business, turning the
esoteric quantum properties of light into
money. But there are a few brave companies that have been trying to do just
that for the last five years, and they may
have hit on the right way to do it. What
these firms, ID Quantique, MagiQ, and
SmartQuantum, are trying to sell is a
way of distributing a cryptographic key
that is theoretically theft-proof, because
it relies on the quirky quantum physics
of photons. Such a "quantum key" distribution system could allow entities
with secrets-banks, large technology
firms, governments, and militaries-
to encode and decode their data for
transmission over optical fiber.
In the hopes of finally gaining customers, the companies involved have retooled
their wares. Some are tying their quantum key distribution technology to highbandwidth commercial devices that can
use the keys to encrypt data. And some
are looking to redesign their systems so
that they can be integrated into telecom
networks to make it more attractive for
big carriers to offer quantum encrypted
lines to their customers.
Quantum key distribution lets two
computers generate a key between them
by taking advantage of a quantum property of photons-the fact that a characteristic such as phase or polarization

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cannot be measured without changing
it. A quantum key can be generated by
transmitting a series of bits encoded
using one or a few photons per bit and
two types of polarization filters.
The bit the photon represents can be
accurately read only by using the right
filter. Use the wrong filter, and you change
the bit. An interloper won't know which
filter the encoder used even though the
sender and receiver can share that information. So the would-be thief can't just
insert himself between the sender and the
receiver to read the bits, and any attempt
he makes to do so will be easily noticed.
Making it even more difficult for such data
thieves, the systems these companies have
developed commonly generate a new key
about once a second.
ID Quantique, a spin-off of the
University of Geneva, debuted the first
commercial key distributor in 2002,
followed quickly by MagiQ Technologies
of New York City. By 2004 those
two were joined by a French start-up,
SmartQuantum, in Lannion. Big firms
such as Mitsubishi, NEC, NTT, and
Toshiba have been researching such
systems as well.
What customers really wanted, says ID
Quantique CEO Grégoire Ribordy, was not
just a key distributor but an integrated
system that could both distribute the keys

and do the data encryption at gigabit-persecond rates-a hybrid of quantum and
classical encryption machines. All three
firms initially focused on developing such
devices in-house.
ID Quantique built a 100-megabitper-second device that distributed keys
on one fiber and transmitted encrypted
data on a second, and MagiQ produced
one that operates at 2 gigabits per second.
Meanwhile, SmartQuantum built a 2-Gb/s
device that did both the key distribution
and the encrypted data transfer on the
same fiber.
But it has proved too difficult for
small start-ups to get such a system on
the market quickly enough to compete
with more established firms selling standard high-bandwidth encryptors. Before
customers will accept a new encryptor,
it must pass a certification process
that can take two or three years, says
SmartQuantum's commercialization and
marketing director, François Guignot. "In
the short term, we do not have the knowledge to develop a fully certified classical
encryption system," he says.
So ID Quantique and SmartQuantum
have shifted gears. Instead of focusing
on building their own encryption
systems, they are partnering with
classical encryption providers to
integrate quantum key distribution into
established products. In January, ID
Quantique announced an arrangement
with Melbourne, Australia-based data
security firm Senetas Corp. that gave
birth to a 1-Gb/s hybrid. In a hybrid, a
single key distributor can serve multiple encryptors. "When your bandwidth

March 2007 | IEEE Spectrum | NA 15

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Table of Contents for the Digital Edition of IEEE Spectrum March, 2007