IEEE - Aerospace and Electronic Systems - March 2021 - 48

An Introduction to Practical Quantum Key Distribution
three units: one " transmitter " and two " receivers. " The
transmitter, which sits between the two receivers, is
responsible for creating two entangled particle pairs, with
one particle each being sent to a receiver. The receivers,
controlled by the end-users A and B, perform measurements on the received states yielding a key.
Communication on their system can be done using traditional optical fibers with key rates of 100 kb/s over
20 km. Longer distances can be utilized, however with a
drop in key-rate performance. Generally, keys should be
used for AES256 encryption, however the application is
outside the scope of the product. Keys are transferred
through a serial interface using the Modbus protocol.
Beyond their primary commercial system, Qubitekk also
produces R&D equipment. One product, the QKD demonstrator, allows for experimental implementation of entanglement-based QKD protocols. As with their primary product,
this system utilizes three boxes. The receivers support an
HDMI output allowing users to visualize the key and error
rate in real time. The system can be configured using a Raspberry Pi 3 but is limited to 1 km at 1 kb/s.
Finally, Qubitekk also produces a " Hacker-box "
which is meant as an add-on device for their QKD demonstrator. This device simulates an adversary performing an
intercept-resend attack in a single basis. To support this,
the device consists of an optical switch; a polarizing
beamsplitter; two SPCs; and one laser source capable of
producing, with high probability, single photons.
Qubitekk, last year, has also created the " quantum
grid " initiative in an effort to commercialize QKD technology developed for the U.S. Department of Energy.
This initiative asked for interested industry partners to participate in a cost-shared field trial program. However,
while preliminary registration for interested participants
has already expired (as of March 2018), it will be interesting to see what reports may come out of this.

QUANTUM XCHANGE
Another U.S. company entering the commercial QKD
field is Quantum XChange (QX). Based in Bethesda, MD,
QX offers to connect clients using QKD devices supplied
by ID Quantique [147] and their own proprietary trusted
node technology developed with Battelle [148]. This service was launched in June, 2018, but as of yet is not publicly available, instead being used by only a select group
of early adopters.
More recently, QX, in partnership with ID Quantique has announced plans to use dark fiber purchased
for the Zayo Group [149], along with their Trusted
Node technology to launch a QKD network spanning
from Boston to Washington D.C. This network, dubbed
Phio [150], would offer QKD-as-a-service to clients
across the eastern seaboard. At the time of writing,
48

there is no information as to the specific capabilities
(key-rates, error-rates, etc.) but this network would be
the largest QKD network in North America and would
allow, for example, QKD secured communication to be
exchanged between traders on Wall Street and their
home offices in New Jersey.

JOINT WORK: FUJITSU, NEC CORP
As mentioned previously in this document, one of the limiting factors of QKD is the efficiency of the single photon
sources used to implement QKD protocols. In 2015, a
joint effort with the University of Tokyo, Fujitsu, and
NEC Corp created new single photon emitters which operate by exciting a quantum dot in a controlled manner causing it to emit photons for an infinitesimally small period of
time. As the time period for which photons can be emitted
is so small, this system reduces the probability of the
source emitting multiple photons to that of one in a million, greatly increasing the efficacy of this source (recall,
multiple photon emissions lead to leaked information to
an adversary).

TELECOM INVESTMENT IN QKD
Many telecommunication companies, globally, have been
showing interest in QKD, and other quantum related
research. Here, we summarize some of the major initiatives over the past decade.
United Kingdom: Beginning in 2016, British Telecom
(BT) and Toshiba have collaborated to open a quantum
communication showcase at a research and development
lab owned by BT in Ipswich [151]. Though BT had been
researching quantum communication for several years
before this; Toshiba has also been highly involved in
quantum research as noted above. Both companies are currently collaborating to build a complete quantum communication network to connect Cambridge, Bristol, London,
and Adastral Park.
Related to the above endeavor is the U.K. National
Quantum Technologies Programme [152]. Begun in 2013,
this program seeks to develop cross-collaboration among
many different research and industry groups to develop
marketable quantum technologies. While primarily consisting of academic groups, they are focused on deriving
commercial systems and working with industry partners.
They were also a lead partner with BT in developing a
QKD link over a distance of 120 km (running through several BT exchanges) in the Cambridge Metropolitan
area [153].
South Korea: SK Telecom has been active in quantum
related research and technology. As recently as February
2018, they invested US $65 million in ID Quantique for
the development of quantum technologies relevant to

IEEE A&E SYSTEMS MAGAZINE

MARCH 2021

IEEE - Aerospace and Electronic Systems - March 2021

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