Research and Development


A higher priority in applications of our high-speed QKD systems is the one for state secret communications. Secure crypto-keys for one-time pad are conventionally delivered by trusted couriers. This system can be replaced with an automatic key delivery by a QKD network. Another important one is an application to secure data-backup communications. After the Great East Japan Earthquake, the importance of business continuity planning and constructing data backup networks for it has been widely recognized. QKD should be used to tightly protect transmission of confidential data between data centers. and to make a mission-critical-secure communications system for the above purposes. We also develop an architecture of secure photonic network to provide multiuser secure services for medical networks, smart community networks, and so on.

We develop secure photonic network architecture by the following four subthemes:

Subtheme 1: Base-line model

We derive baseline models for point-to-point link and point-to-multipoint network, which define the elements and specifications of the network, taking into account target applications. Figure 1 depicts a rough image of a baseline model.

Subtheme 2: Application of related peripheral technologies for management

A secure photonic network must provide functions, such as authentication, key distribution and synchronization between several nodes, management of valid key. We develop an architecture for QKD network by integrating and customizing various technologies developed in modern cryptographic networks. The result will be integrated with quantum technology developed in subtheme 3.

Subtheme 3: Quantum cryptography technology for secure network management

We explore quantum cryptographic technology useful to construct secure network. We collaborate with Subjects 157A, 157B, and 157C, to modify the QKD system suitable to be adopted in the network. Finally, subtheme 2 and subtheme 3 develop optimized architecture in terms of security and network resource.

Subtheme 4: Construction of test environment / Operation verification

We evaluate technologies developed by subtheme 2 and subtheme 3 in practice. We develop a test environment according to the base-line model defined in subtheme 1.

We study methods to combine the QKD technologies from Subjects 157A, 157B and 157C.

We construct a test service network according to the specification of the systems developed by Subjects 157A, 157B and 157C. It includes a sensor network system to monitor environmental conditions of optical fibers, interfaces, and status of the key management server and agents. Through test runs, data for quality guarantee of our secure photonic network will be extracted.


Fig. 1Concept


Final results for Team 157D-T01

Task title Outcome Date Note
1: Research for baseline model
(Fig. 2-1,2-2,3,4)
We defined communication model of 1 to 1 and communication model of 1 vs. many as a baseline model. Oct. 2013  
We defined a three-layered structure (QKD layer, key management layer and key supply layer) and I/Fs between each layer for key distribution. Mar. 2016 It became possible to supply secure-key from QKD equipment to various applications. Administration of key supply and applications were separated.
QKD platform: key supplier
Applications: key user
We confirmed that an optical fiber tapping and an obstacle can be detected by statistics informations of QKD (QBER, key generation rate) monitoring. Mar. 2016  
2: Application of related technologies for management
(Fig. 5-1,5-2)
We have developed applications to prove the baseline model (Layer 2 network encryptors and Encrypted smartphone). Mar. 2016  
We introduced authentication systems for key synchronization and identification in the QKD platform (Wegman-Carter authentication). Mar. 2016  
We implemented general-purpose physical I/F for key supply. Mar. 2016  
3: Quantum technology for secure network management
(Fig. 6)
We have developed method and technique to characterize working QKD machines. Mar. 2016  
We proposed a key relay protocol using less-trusted nodes, with the help of classical secret sharing. Mar. 2015  
We have developed low-cost photon detectors for monitoring QKD equipment. Mar. 2015  
We proposed entanglement recovering from bound entanglement by super-activation. Mar. 2014  
4: Construction of test environment/ Operation verification
(Fig. 4,7,8,9,10)
We integrated the research results of Subject 157A and 157C which were improved by suggestion from Subject 157B, and constructed the proof environment which consists of 5 nodes (Tokyo QKD Network). Mar. 2016  
We constructed a sensor network system to monitor environmental climate, where temperature and other climate data are displayed. We examined the effects of the climate on the performances of the QKD systems. Mar. 2016  
When detecting a fiber tapping or an obstacle, the most suitable route of a key relay was selected and the route was switched automatically. We added the function to find the location of the tapping or the obstacle. Mar. 2016  

Figure 2-1

Fig. 2-1Communication model of 1 to 1

Figure 2-2

Fig. 2-2Communication model of 1 to many

Figure 3

Fig. 3Three layer structure for qucantum key distribution

Figure 4
  • (1) QKD-key is generated at (Red line) between Koganei-1 – Koganei-3 via Koganei-4.
  • (2) Tapping occurs between Koganei-1 – Koganei-4.
  • (3) A route is changed to (purple line) between Koganei-1 – Koganei-3 via Koganei-2 and Koganei-4.

Fig. 4Tokyo QKD Network

We have developed applications to prove the baseline model (Layer 2 network encryptors and Encrypted smartphone).

Figure 5-1

Fig. 5-1Integration with NEC's layer 2 network encryptor product COMCIPHER(AES)

Figure 5-2

Fig. 5-2Multiuser-adoptive encrypted smartphone

Figure 6 link area for fig 6: Risk of trusted node key relay link area for fig 6: Solution with group secter sharing link area for fig 6: A simple receiver design with a balanced mixer

Fig. 6Quantum technology for secure network management

 Risk of trusted node key relay   A simple receiver design with a balanced mixer   Only one compromised node leaks all information   Solution with group secter sharing   A photon detector works without sharp filter   Key is distributed many nodes, which can be regenerated by classical distributed computing.
Nodes can be compromised up to threshold number 

Construction of test environment in collaboration with Subject 157A, 157B and 157C

Figure 7

Fig. 7Tokyo QKD Network

Construction of test environment in collaboration with Subject 157A, 157B, and 157C

Figure 8  NEC's QKD equipment operates stably despite the change of temperature and climate 

Fig. 8Temperature and climate effect

Figure 9

Fig. 9open Web site(1/2) link to the page

Figure 10

Fig. 10open Web site(2/2) in detail


item pointWe developed the secure network which combined modern cipher with quantum key distribution, and demonstrated secure communications on the Tokyo QKD Network in cooperation with Subject 157A and 157C.

item pointWe will make effort to expand and diffuse the development of finding through ImPACT (FY2014-2018) project.