Corporate Research & Development Center

Toshiba verifies a system for distributing quantum encryption keys between multiple transmitters and a single receiver for the first time in the world



Quantum encryption key distribution is a cryptographic technology which ensures data security by utilizing the quantum mechanical properties of photons. Previous research and development of quantum encryption key distribution has been conducted using a system for connecting one transmitter with one receiver. However, for the first time in the world the Cambridge Research Laboratory of Toshiba Research Europe has succeeded in testing and verifying a technique for distributing quantum encryption keys using a system connecting one receiver with multiple transmitters (quantum access network) based on its own high-speed photon detection technology. This result was published in Nature, one of the most prestigious scientific magazines in the world.

Development background

Previous studies on quantum encryption key distribution technology have been conducted using a system connecting one transmitter with one receiver, but this requires as many communication paths as the number of users. The center communicating with multiple users must provide an optical fiber wire and receiver for each user of the quantum encryption key distribution system, making the system impractical.

Quantum access network

To solve this problem, Toshiba developed the quantum access network technology, in which one receiver is connected with multiple transmitters, and tested and verified its effect. Specifically, we used our own technology to detect a photon every nanosecond and succeeded in detecting photons from multiple users in one receiver. We also designed the transmitter to actively eliminate the effect of changes of fiber length due to temperature deviation to ensure stable and continuous communication. This time, we connected two transmitters with one optical splitter to communicate with one receiver through one optical fiber. As a result, we confirmed the feasibility of transmitting quantum encryption keys at more than 250 kilobits per second, with stable operation for 12 hours and connection with up to 64 users. The quantum access network technology allows users to create a network, which collects signals from multiple users and sends them through one fiber to the center, using standard optical communication parts. The technology will satisfy the needs of users who want to reduce costs and space, without having to install receivers, in order to build a system based on quantum encryption key distribution.


We are verifying a quantum access network that allows access to more users with faster distribution of quantum encryption keys, and are confirming the usability of the technology in field tests.

* A part of the result was obtained through “Research and development on secure photonic network technology” run by the National Institute of Information and Communications Technology (NICT).