IEEE - Aerospace and Electronic Systems - March 2021 - 49

Amer et al.
telecom and also IoT markets. Before this, SK Telecom
has been actively partnering with IDQ having invested $2
million in 2016 and in 2017 they developed the world's
smallest quantum random number generator using technology licensed from IDQ [154].
SK Telecom is also planning to use technology from
ID Quantique in their future 5G network. Specifically,
they plan to apply this technology, first, to the SeoulAnsan section of its upcoming 5G network; they plan to
then expand and apply this technology to their customer
authentication server in early 2019 [155].
Having established their Quantum Technology Lab in
2011 specifically devoted to quantum technologies, SK
Telecom has been actively involved in the research and
development of quantum repeaters (needed to increase the
range of QKD networks without the use of trusted nodes).
They also applied quantum cryptography technology to
their commercial LTE network in Sejong City [156], [157].
Nippon Telegraph and Telephone Corporation (NTT):
NTT has been actively investing, since 2003 [158] in
quantum related technology and research. Most recent, in
2015, their researchers proposed an " all photonic intercity
QKD system. " This system requires A and B to send photons to a central server which will perform Bell measurements. The outcome of this measurement, announced by
the server, allows for A and B to share a correlated bit,
without the server actually knowing what that bit is. They
have been active in other areas of protocol development
also, including the development of a " Round-Robin Differential Phase Shift " protocol which can operate without
the need to constantly monitor error rates [159], [160].
In 2017, it was announced, in partnership with the
National Institute of Informatics and the University of
Tokyo, to construct a Quantum Neural Network based
computer. Their computer, using optical quantum computation, will also be made available to the public through a
cloud-based interface. The work in [161] and[162] while
not directly related to QKD, it shows their interest in general quantum technology.
Deutsche Telekom: Deutsche Telekom, partnering
with South Korea Telecom, created the Quantum Alliance
in 2017 to counter the threat posed by eventual development of quantum computers. Their initiative is currently
recruiting partners, including network operators and
equipment makers, to join their effort with a target to
develop commercial products [163].
As of October 2018, they are also investing in ID
Quantique (part of a joint agreement with SK Telecom) in
order to strengthen the competitiveness and security in 5G
services, the goal being to apply quantum cryptographic
services, with hardware developed by ID Quantique, to
future 5G operations [164].
Again, in partnership with SK Telecom, Deutsche Telekom is planning to incorporate quantum communication
technology, consisting of QKD nodes and quantum
MARCH 2021

random number generators, to a trial network. Their plan
is to incorporate this technology for commercial communication within their network [165], [166].

CLOSING REMARKS
QKD is a highly promising field of research and development. From humble beginnings in the 1980s, it is currently
seeing massive interest in the research community with
the development of more efficient protocols; the experimental community, with the demonstration of QKD over
various communication modes, including fiber, over-theair with mobile targets, and even satellites; and the commercial industry through the creation of several commercial QKD products in use today. It is also a technology
that is highly cross-disciplinary with numerous advances
made by fields not directly related to quantum physics.
While still, perhaps, in the relative early stages, this technology continues to grow in prominence and, we suspect,
will be highly visible in the very near future. There are
still several fascinating problems that remain open, some
of which were highlighted throughout this article; of particular interest and importance are improving efficiency
and distance along with combining alternative technologies to adapt QKD to new operating conditions and applications. With this survey paper, by focusing on a highlevel overview of this field, along with current practical
implementations, we hope to expand interest of QKD to
researchers and practitioners in many other fields so as to
further speed up its growth and eventual wide-scale
adoption.

ACKNOWLEDGMENTS
Walter O. Krawec and Omar Amer would like to thank the
Comcast Innovation Fund for their support. The authors
would also like to thank P. Quesada and B. Rashidi for
reading early versions of this article and providing very
valuable feedback which greatly improved its quality.
Finally, the authors would like to thank the anonymous
reviewers for their time and valuable comments which
greatly improved the quality of this article.

REFERENCES
[1] J. Katz and Y. Lindell, Introduction to Modern Cryptography. Boca Raton, FL, USA: CRC Press, 2014.
[2] W. Stallings, Network Security Essentials: Applications
and Standards. London, U.K.: Pearson, 2007.
[3] C. H. Bennett and G. Brassard, " Quantum cryptography: Public
key distribution and coin tossing, " in Proc. IEEE Int. Conf.
Comput., Syst. Signal Process., 1984, vol. 175, pp. 175-179.
[4] S. Wiesner, " Conjugate coding, " ACM Sigact News,
vol. 15, no. 1, pp. 78-88, 1983.

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