Researchers at the National Institute of Standards and Technology want cut the cost of quantum cryptography.A team of researchers at the National Institute of Standards and Technology is
touting a new method of cutting the costs associated with quantum key
distribution.
In a soon-to-be-published paper, researchers at NIST outline a technique
that simplifies the structure of a QKD system, slashing its costs by reducing
the number of single photon detectors it needs.
In the paper, which will be published next month in IEEE Communications
Letters, researchers present a DTBS (detection-time-bin-shift) scheme based on
their previously developed conventional fiber-based QKD system.
DTBS uses time-division multiplexing of a single photon detector between two
photon bases in a QKD system. The researchers’ DTBS QKD system generated sifted
keys at a rate of more than 1M bps with a quantum bit error rate of less than 2
percent over 1.1 kilometers of fiber.
Quantum cryptography uses the principles of quantum mechanics to enable two
parties to produce a shared random bit string known only to them to encrypt and
decrypt messages. QKD is considered by many to be highly secure because it
enables the two communicating users to detect any attempts by an outside party
to gain knowledge of the key. However, the price of implementation can be a
barrier for many enterprises, said NIST researcher Xiao Tang.
Check out these 10 ways employees put your company at risk.
With quantum cryptography, "I would say the technology itself is there,
[and it is] very clear how to do it,” he said. “Still, when you want to have an
experimental result transfer to the market, there are a lot of steps to do, and
one of the most important things is just [to] reduce the cost, [and] then it
would make it easier to make it a product.”
In quantum cryptography, a recipient needs to measure a sequence of photons,
or particles of light transmitted by the sender. In the most common
polarization-based protocol, known as BB84, the recipient uses four
single-photon detectors at a cost of roughly $5,000 to $20,000 each, according
to NIST. One pair of detectors records photons with horizontal and vertical
polarization, which could indicate 0 and 1, respectively. The other pair
detects photons with diagonal, or plus or minus 45 degree polarization, in
which the northeast and northwest directions alternatively denote 0 and 1.
In the new method, the researchers set up an optical component to make the
diagonally polarized photons rotate another 45 degrees so they arrive later and
in a separate time bin at the same detector than the horizontal/vertical polarized
ones. Therefore, one pair of detectors can be used to record information from
both kinds of polarized photons in succession, reducing the required number of
detectors from four to two. In another protocol, called B92, the researchers
were able to cut the necessary number of detectors from two to one.
Since writing the paper, the researchers have gone a step further so that
the BB84 method now only requires one detector instead of four.
“In the beginning QKD is just point to point, only two parties talk to each
other,” Tang said. “Now we’re trying to build a network. In our laboratory we
actually demonstrated three users, which is a very simple network, but it’s
very complicated technology. ... The next step will be how to use this kind of
setup [in] the existing fiber network environment.”
